> -----Original Message-----
> From: Richard Biener <rguent...@suse.de>
> Sent: Wednesday, February 26, 2025 12:30 PM
> To: Tamar Christina <tamar.christ...@arm.com>
> Cc: gcc-patches@gcc.gnu.org; nd <n...@arm.com>
> Subject: Re: [3/3 PATCH v3]middle-end: delay checking for alignment to load
> [PR118464]
> 
> On Tue, 25 Feb 2025, Tamar Christina wrote:
> 
> > Hi All,
> >
> > This fixes two PRs on Early break vectorization by delaying the safety 
> > checks to
> > vectorizable_load when the VF, VMAT and vectype are all known.
> >
> > This patch does add two new restrictions:
> >
> > 1. On LOAD_LANES targets, where the buffer size is known, we reject uneven
> >    group sizes, as they are unaligned every n % 2 iterations and so may 
> > cross
> >    a page unwittingly.
> >
> > 2. On LOAD_LANES targets when the buffer is unknown, we reject vectorization
> if
> >    we cannot peel for alignment, as the alignment requirement is quite 
> > large at
> >    GROUP_SIZE * vectype_size.  This is unlikely to ever be beneficial so we
> >    don't support it for now.
> >
> > There are other steps documented inside the code itself so that the 
> > reasoning
> > is next to the code.
> >
> > Note that for VLA I have still left this fully disabled when not working on 
> > a
> > fixed buffer.
> >
> > For VLA targets like SVE return element alignment as the desired vector
> > alignment.  This means that the loads are never misaligned and so annoying 
> > it
> > won't ever need to peel.
> >
> > So what I think needs to happen in GCC 16 is that.
> >
> > 1. during vect_compute_data_ref_alignment we need to take the max of
> >    POLY_VALUE_MIN and vector_alignment.
> >
> > 2. vect_do_peeling define skip_vector when PFA for VLA, and in the guard 
> > add a
> >    check that ncopies * vectype does not exceed POLY_VALUE_MAX which we use
> as a
> >    proxy for pagesize.
> >
> > 3. Force LOOP_VINFO_USING_PARTIAL_VECTORS_P to be true in
> >    vect_determine_partial_vectors_and_peeling since the first iteration has 
> > to
> >    be partial. If LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P we have to fail to
> >    vectorize.
> >
> > 4. Create a default mask to be used, so that
> vect_use_loop_mask_for_alignment_p
> >    becomes true and we generate the peeled check through loop control for
> >    partial loops.  From what I can tell this won't work for
> >    LOOP_VINFO_FULLY_WITH_LENGTH_P since they don't have any peeling
> support at
> >    all in the compiler.  That would need to be done independently from the
> >    above.
> >
> > In any case, not GCC 15 material so I've kept the WIP patches I have
> downstream.
> >
> > Bootstrapped Regtested on aarch64-none-linux-gnu,
> > arm-none-linux-gnueabihf, x86_64-pc-linux-gnu
> > -m32, -m64 and no issues.
> >
> > Ok for master?
> >
> > Thanks,
> > Tamar
> >
> > gcc/ChangeLog:
> >
> >     PR tree-optimization/118464
> >     PR tree-optimization/116855
> >     * doc/invoke.texi (min-pagesize): Update docs with vectorizer use.
> >     * tree-vect-data-refs.cc (vect_analyze_early_break_dependences): Delay
> >     checks.
> >     (vect_compute_data_ref_alignment): Remove alignment checks and move
> to
> >     get_load_store_type, increase group access alignment.
> >     (vect_enhance_data_refs_alignment): Add note to comment needing
> >     investigating.
> >     (vect_analyze_data_refs_alignment): Likewise.
> >     (vect_supportable_dr_alignment): For group loads look at first DR.
> >     * tree-vect-stmts.cc (get_load_store_type):
> >     Perform safety checks for early break pfa.
> >     * tree-vectorizer.h (dr_set_safe_speculative_read_required,
> >     dr_safe_speculative_read_required, DR_SCALAR_KNOWN_BOUNDS):
> New.
> >     (need_peeling_for_alignment): Renamed to...
> >     (safe_speculative_read_required): .. This
> >     (class dr_vec_info): Add scalar_access_known_in_bounds.
> >
> > gcc/testsuite/ChangeLog:
> >
> >     PR tree-optimization/118464
> >     PR tree-optimization/116855
> >     * gcc.dg/vect/bb-slp-pr65935.c: Update, it now vectorizes because the
> >     load type is relaxed later.
> >     * gcc.dg/vect/vect-early-break_121-pr114081.c: Update.
> >     * gcc.dg/vect/vect-early-break_22.c: Reject for load_lanes targets
> >     * g++.dg/vect/vect-early-break_7-pr118464.cc: New test.
> >     * gcc.dg/vect/vect-early-break_132-pr118464.c: New test.
> >     * gcc.dg/vect/vect-early-break_133_pfa1.c: New test.
> >     * gcc.dg/vect/vect-early-break_133_pfa10.c: New test.
> >     * gcc.dg/vect/vect-early-break_133_pfa2.c: New test.
> >     * gcc.dg/vect/vect-early-break_133_pfa3.c: New test.
> >     * gcc.dg/vect/vect-early-break_133_pfa4.c: New test.
> >     * gcc.dg/vect/vect-early-break_133_pfa5.c: New test.
> >     * gcc.dg/vect/vect-early-break_133_pfa6.c: New test.
> >     * gcc.dg/vect/vect-early-break_133_pfa7.c: New test.
> >     * gcc.dg/vect/vect-early-break_133_pfa8.c: New test.
> >     * gcc.dg/vect/vect-early-break_133_pfa9.c: New test.
> >     * gcc.dg/vect/vect-early-break_39.c: Update testcase for misalignment.
> >     * gcc.dg/vect/vect-early-break_53.c: Likewise.
> >     * gcc.dg/vect/vect-early-break_56.c: Likewise.
> >     * gcc.dg/vect/vect-early-break_57.c: Likewise.
> >     * gcc.dg/vect/vect-early-break_81.c: Likewise.
> >
> > ---
> > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> > index
> ca8e468f3f2dbf68c959f74d8fec48c79463504d..fff2874b326d605fc2656adf4ab
> 6eb5bd5d42d71 100644
> > --- a/gcc/doc/invoke.texi
> > +++ b/gcc/doc/invoke.texi
> > @@ -17256,7 +17256,7 @@ Maximum number of relations the oracle will
> register in a basic block.
> >  Work bound when discovering transitive relations from existing relations.
> >
> >  @item min-pagesize
> > -Minimum page size for warning purposes.
> > +Minimum page size for warning and early break vectorization purposes.
> >
> >  @item openacc-kernels
> >  Specify mode of OpenACC `kernels' constructs handling.
> > diff --git a/gcc/testsuite/gcc.dg/vect/bb-slp-pr65935.c
> b/gcc/testsuite/gcc.dg/vect/bb-slp-pr65935.c
> > index
> 9ef1330b47c817e16baaafa44c2b15108b9dd3a9..4c8255895b976653228233d
> 93c950629f3231554 100644
> > --- a/gcc/testsuite/gcc.dg/vect/bb-slp-pr65935.c
> > +++ b/gcc/testsuite/gcc.dg/vect/bb-slp-pr65935.c
> > @@ -55,7 +55,9 @@ int main()
> >       }
> >      }
> >    rephase ();
> > +#pragma GCC novector
> >    for (i = 0; i < 32; ++i)
> > +#pragma GCC novector
> >      for (j = 0; j < 3; ++j)
> >  #pragma GCC novector
> >        for (k = 0; k < 3; ++k)
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_121-pr114081.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_121-pr114081.c
> > index
> 423ff0b566b18bf04ce4f67a45b94dc1a021a4a0..f99c57be0adc4d49035b8a75c
> 72d4a5b04cc05c7 100644
> > --- a/gcc/testsuite/gcc.dg/vect/vect-early-break_121-pr114081.c
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_121-pr114081.c
> > @@ -5,7 +5,8 @@
> >  /* { dg-additional-options "-O3" } */
> >  /* { dg-additional-options "-mavx2" { target { x86_64-*-* i?86-*-* } } } */
> >
> > -/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> > +/* Arm and -m32 create a group size of 3 here, which we can't support yet.
> AArch64 makes elementwise accesses here.  */
> > +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" { target { 
> > aarch64*-*-
> * } } } } */
> >
> >  typedef struct filter_list_entry {
> >    const char *name;
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_132-pr118464.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_132-pr118464.c
> > new file mode 100644
> > index
> 0000000000000000000000000000000000000000..9bf0cbc8853f74de550e8a
> c83ab569fc9fbde126
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_132-pr118464.c
> > @@ -0,0 +1,25 @@
> > +/* { dg-do compile } */
> > +/* { dg-add-options vect_early_break } */
> > +/* { dg-require-effective-target vect_early_break } */
> > +/* { dg-require-effective-target vect_int } */
> > +/* { dg-additional-options "-O3" } */
> > +
> > +int a, b, c, d, e, f;
> > +short g[1];
> > +int main() {
> > +  int h;
> > +  while (a) {
> > +    while (h)
> > +      ;
> > +    for (b = 2; b; b--) {
> > +      while (c)
> > +        ;
> > +      f = g[a];
> > +      if (d)
> > +        break;
> > +    }
> > +    while (e)
> > +      ;
> > +  }
> > +  return 0;
> > +}
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa1.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa1.c
> > new file mode 100644
> > index
> 0000000000000000000000000000000000000000..dc771186efafe25bb65490
> da7a383ad7f6ceb0a7
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa1.c
> > @@ -0,0 +1,19 @@
> > +/* { dg-do compile } */
> > +/* { dg-add-options vect_early_break } */
> > +/* { dg-require-effective-target vect_early_break } */
> > +/* { dg-require-effective-target vect_int } */
> > +/* { dg-additional-options "-O3" } */
> > +
> > +char string[1020];
> > +
> > +char * find(int n, char c)
> > +{
> > +    for (int i = 1; i < n; i++) {
> > +        if (string[i] == c)
> > +            return &string[i];
> > +    }
> > +    return 0;
> > +}
> > +
> > +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> > +/* { dg-final { scan-tree-dump "Alignment of access forced using peeling" 
> > "vect"
> } } */
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa10.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa10.c
> > new file mode 100644
> > index
> 0000000000000000000000000000000000000000..82d473a279ce060c55028
> 9c61729d9f9b56f0d2a
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa10.c
> > @@ -0,0 +1,24 @@
> > +/* { dg-add-options vect_early_break } */
> > +/* { dg-do compile } */
> > +/* { dg-require-effective-target vect_early_break } */
> > +/* { dg-require-effective-target vect_int } */
> > +
> > +/* { dg-additional-options "-Ofast" } */
> > +
> > +/* Alignment requirement too big, load lanes targets can't safely 
> > vectorize this.
> */
> > +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" { target { !
> vect_load_lanes } } } } */
> > +/* { dg-final { scan-tree-dump-not "Alignment of access forced using 
> > peeling"
> "vect" { target { ! vect_load_lanes } } } } */
> > +
> > +unsigned test4(char x, char *restrict vect_a, char *restrict vect_b, int n)
> > +{
> > + unsigned ret = 0;
> > + for (int i = 0; i < (n - 2); i+=2)
> > + {
> > +   if (vect_a[i] > x || vect_a[i+2] > x)
> > +     return 1;
> > +
> > +   vect_b[i] = x;
> > +   vect_b[i+1] = x+1;
> > + }
> > + return ret;
> > +}
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa2.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa2.c
> > new file mode 100644
> > index
> 0000000000000000000000000000000000000000..7d56772fbf380ce42ac758
> ca29a5f3f9d3f6e0d1
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa2.c
> > @@ -0,0 +1,19 @@
> > +/* { dg-do compile } */
> > +/* { dg-add-options vect_early_break } */
> > +/* { dg-require-effective-target vect_early_break } */
> > +/* { dg-require-effective-target vect_int } */
> > +/* { dg-additional-options "-O3" } */
> > +
> > +char string[1020];
> > +
> > +char * find(int n, char c)
> > +{
> > +    for (int i = 0; i < n; i++) {
> > +        if (string[i] == c)
> > +            return &string[i];
> > +    }
> > +    return 0;
> > +}
> > +
> > +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> > +/* { dg-final { scan-tree-dump-not "Alignment of access forced using 
> > peeling"
> "vect" } } */
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa3.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa3.c
> > new file mode 100644
> > index
> 0000000000000000000000000000000000000000..374a051b945e97eedb9be
> 9da423cf54b5e564d6f
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa3.c
> > @@ -0,0 +1,20 @@
> > +/* { dg-do compile } */
> > +/* { dg-add-options vect_early_break } */
> > +/* { dg-require-effective-target vect_early_break } */
> > +/* { dg-require-effective-target vect_int } */
> > +/* { dg-additional-options "-O3" } */
> > +
> > +char string[1020] __attribute__((aligned(1)));
> > +
> > +char * find(int n, char c)
> > +{
> > +    for (int i = 1; i < n; i++) {
> > +        if (string[i] == c)
> > +            return &string[i];
> > +    }
> > +    return 0;
> > +}
> > +
> > +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> > +/* { dg-final { scan-tree-dump "Alignment of access forced using peeling" 
> > "vect"
> } } */
> > +/* { dg-final { scan-tree-dump "force alignment of string" "vect" } } */
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa4.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa4.c
> > new file mode 100644
> > index
> 0000000000000000000000000000000000000000..297fb7e9b9beffa25ab8f25
> 7ceea1c065fcc6ae9
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa4.c
> > @@ -0,0 +1,20 @@
> > +/* { dg-do compile } */
> > +/* { dg-add-options vect_early_break } */
> > +/* { dg-require-effective-target vect_early_break } */
> > +/* { dg-require-effective-target vect_int } */
> > +/* { dg-additional-options "-O3" } */
> > +
> > +char string[1020] __attribute__((aligned(1)));
> > +
> > +char * find(int n, char c)
> > +{
> > +    for (int i = 0; i < n; i++) {
> > +        if (string[i] == c)
> > +            return &string[i];
> > +    }
> > +    return 0;
> > +}
> > +
> > +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> > +/* { dg-final { scan-tree-dump-not "Alignment of access forced using 
> > peeling"
> "vect" } } */
> > +/* { dg-final { scan-tree-dump "force alignment of string" "vect" } } */
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa5.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa5.c
> > new file mode 100644
> > index
> 0000000000000000000000000000000000000000..ca95be44e92e32769da1d
> 1e9b740ae54682a3d55
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa5.c
> > @@ -0,0 +1,23 @@
> > +/* { dg-add-options vect_early_break } */
> > +/* { dg-do compile } */
> > +/* { dg-require-effective-target vect_early_break } */
> > +/* { dg-require-effective-target vect_int } */
> > +
> > +/* { dg-additional-options "-Ofast" } */
> > +
> > +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> > +
> > +unsigned test4(char x, char *vect, int n)
> > +{
> > + unsigned ret = 0;
> > + for (int i = 0; i < n; i++)
> > + {
> > +   if (vect[i] > x)
> > +     return 1;
> > +
> > +   vect[i] = x;
> > + }
> > + return ret;
> > +}
> > +
> > +/* { dg-final { scan-tree-dump "Alignment of access forced using peeling" 
> > "vect"
> } } */
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa6.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa6.c
> > new file mode 100644
> > index
> 0000000000000000000000000000000000000000..ee123df6ed2ba97e92307c
> 64a61c97b1b6268743
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa6.c
> > @@ -0,0 +1,23 @@
> > +/* { dg-add-options vect_early_break } */
> > +/* { dg-do compile } */
> > +/* { dg-require-effective-target vect_early_break } */
> > +/* { dg-require-effective-target vect_int } */
> > +
> > +/* { dg-additional-options "-Ofast" } */
> > +
> > +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> > +
> > +unsigned test4(char x, char *vect_a, char *vect_b, int n)
> > +{
> > + unsigned ret = 0;
> > + for (int i = 1; i < n; i++)
> > + {
> > +   if (vect_a[i] > x || vect_b[i] > x)
> > +     return 1;
> > +
> > +   vect_a[i] = x;
> > + }
> > + return ret;
> > +}
> > +
> > +/* { dg-final { scan-tree-dump "Versioning for alignment will be applied" 
> > "vect" }
> } */
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa7.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa7.c
> > new file mode 100644
> > index
> 0000000000000000000000000000000000000000..51bad4e745b67cfdaad20f
> 50776299531824ce9c
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa7.c
> > @@ -0,0 +1,23 @@
> > +/* { dg-add-options vect_early_break } */
> > +/* { dg-do compile } */
> > +/* { dg-require-effective-target vect_early_break } */
> > +/* { dg-require-effective-target vect_int } */
> > +
> > +/* { dg-additional-options "-Ofast" } */
> > +
> > +/* This should be vectorizable through load_lanes and linear targets.  */
> > +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> > +
> > +unsigned test4(char x, char * restrict vect_a, char * restrict vect_b, int 
> > n)
> > +{
> > + unsigned ret = 0;
> > + for (int i = 0; i < n; i+=2)
> > + {
> > +   if (vect_a[i] > x || vect_a[i+1] > x)
> > +     return 1;
> > +
> > +   vect_b[i] = x;
> > +   vect_b[i+1] = x+1;
> > + }
> > + return ret;
> > +}
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa8.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa8.c
> > new file mode 100644
> > index
> 0000000000000000000000000000000000000000..dbb14ba3239c91b9bfdf56
> cecc60750394e10f2b
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa8.c
> > @@ -0,0 +1,25 @@
> > +/* { dg-add-options vect_early_break } */
> > +/* { dg-do compile } */
> > +/* { dg-require-effective-target vect_early_break } */
> > +/* { dg-require-effective-target vect_int } */
> > +
> > +/* { dg-additional-options "-Ofast" } */
> > +
> > +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> > +
> > +char vect_a[1025];
> > +char vect_b[1025];
> > +
> > +unsigned test4(char x, int n)
> > +{
> > + unsigned ret = 0;
> > + for (int i = 1; i < (n - 2); i+=2)
> > + {
> > +   if (vect_a[i] > x || vect_a[i+1] > x)
> > +     return 1;
> > +
> > +   vect_b[i] = x;
> > +   vect_b[i+1] = x+1;
> > + }
> > + return ret;
> > +}
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa9.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa9.c
> > new file mode 100644
> > index
> 0000000000000000000000000000000000000000..31e209620925353948325
> 3efc17499a53d112894
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_133_pfa9.c
> > @@ -0,0 +1,28 @@
> > +/* { dg-add-options vect_early_break } */
> > +/* { dg-do compile } */
> > +/* { dg-require-effective-target vect_early_break } */
> > +/* { dg-require-effective-target vect_int } */
> > +
> > +/* { dg-additional-options "-Ofast" } */
> > +
> > +/* Group size is uneven, load lanes targets can't safely vectorize this.  
> > */
> > +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> > +/* { dg-final { scan-tree-dump-not "Alignment of access forced using 
> > peeling"
> "vect" } } */
> > +
> > +
> > +char vect_a[1025];
> > +char vect_b[1025];
> > +
> > +unsigned test4(char x, int n)
> > +{
> > + unsigned ret = 0;
> > + for (int i = 1; i < (n - 2); i+=2)
> > + {
> > +   if (vect_a[i-1] > x || vect_a[i+2] > x)
> > +     return 1;
> > +
> > +   vect_b[i] = x;
> > +   vect_b[i+1] = x+1;
> > + }
> > + return ret;
> > +}
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_39.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_39.c
> > index
> 9d3c6a5dffe3be4a7759b150e330d18144ab5ce5..b3f40b8c9ba49e41bd283e46
> a462238c3b5825ef 100644
> > --- a/gcc/testsuite/gcc.dg/vect/vect-early-break_39.c
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_39.c
> > @@ -23,4 +23,5 @@ unsigned test4(unsigned x, unsigned n)
> >   return ret;
> >  }
> >
> > -/* { dg-final { scan-tree-dump "vectorized 1 loops in function" "vect" } } 
> > */
> > +/* cannot safely vectorize this due due to the group misalignment.  */
> > +/* { dg-final { scan-tree-dump-times "vectorized 1 loops in function" 0 
> > "vect" } }
> */
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_53.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_53.c
> > index
> a02d5986ba3cfc117b19305c5e96711299996931..d4fd0d39a25a5659e3d9452
> b79f3e0fabba8b3c0 100644
> > --- a/gcc/testsuite/gcc.dg/vect/vect-early-break_53.c
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_53.c
> > @@ -2,6 +2,7 @@
> >  /* { dg-do compile } */
> >  /* { dg-require-effective-target vect_early_break } */
> >  /* { dg-require-effective-target vect_int } */
> > +/* { dg-require-effective-target vect_partial_vectors } */
> >
> >  void abort ();
> >  int a[64], b[64];
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_56.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_56.c
> > index
> 9096f66647c7b3cb430562d35f8ce076244f7c11..b35e737fa3b9137cd745c14f
> 7ad915a3f81c38c4 100644
> > --- a/gcc/testsuite/gcc.dg/vect/vect-early-break_56.c
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_56.c
> > @@ -4,6 +4,7 @@
> >  /* { dg-require-effective-target vect_int } */
> >  /* { dg-add-options bind_pic_locally } */
> >  /* { dg-require-effective-target vect_early_break_hw } */
> > +/* { dg-require-effective-target vect_partial_vectors } */
> >
> >  #include <stdarg.h>
> >  #include "tree-vect.h"
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_57.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_57.c
> > index
> 319bd125c3156f13c300ff2b94d269bb9ec29e97..a4886654f152b2c0568286fe
> bea2b31cb7be8499 100644
> > --- a/gcc/testsuite/gcc.dg/vect/vect-early-break_57.c
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_57.c
> > @@ -5,8 +5,9 @@
> >
> >  /* { dg-additional-options "-Ofast" } */
> >
> > -/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> > -/* { dg-final { scan-tree-dump "epilog loop required" "vect" } } */
> > +/* Multiple loads of different alignments, we can't peel this. */
> > +/* { dg-final { scan-tree-dump-not "LOOP VECTORIZED" "vect" } } */
> > +/* { dg-final { scan-tree-dump-not "epilog loop required" "vect" } } */
> >
> >  void abort ();
> >
> > diff --git a/gcc/testsuite/gcc.dg/vect/vect-early-break_81.c
> b/gcc/testsuite/gcc.dg/vect/vect-early-break_81.c
> > index
> 8a8c076ba92ca6fef419cb23b457a23555c61c64..b58a4611d6b8d86f0247d9ea
> 44ab4750473589a9 100644
> > --- a/gcc/testsuite/gcc.dg/vect/vect-early-break_81.c
> > +++ b/gcc/testsuite/gcc.dg/vect/vect-early-break_81.c
> > @@ -5,8 +5,9 @@
> >
> >  /* { dg-additional-options "-Ofast" } */
> >
> > -/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" } } */
> > -/* { dg-final { scan-tree-dump "epilog loop required" "vect" } } */
> > +/* Multiple loads with different misalignments.  Can't peel need partial 
> > loop
> support.  */
> > +/* { dg-final { scan-tree-dump-not "LOOP VECTORIZED" "vect" } } */
> > +/* { dg-final { scan-tree-dump-not "epilog loop required" "vect" } } */
> >  void abort ();
> >
> >  unsigned short sa[32];
> > diff --git a/gcc/tree-vect-data-refs.cc b/gcc/tree-vect-data-refs.cc
> > index
> 6d5854ac7c7a18e09ec7ad72c534abdc55cb6efa..3df48c8611c8fd843efb145c7c
> 1a0afeee25edfa 100644
> > --- a/gcc/tree-vect-data-refs.cc
> > +++ b/gcc/tree-vect-data-refs.cc
> > @@ -731,7 +731,9 @@ vect_analyze_early_break_dependences (loop_vec_info
> loop_vinfo)
> >       if (is_gimple_debug (stmt))
> >         continue;
> >
> > -     stmt_vec_info stmt_vinfo = loop_vinfo->lookup_stmt (stmt);
> > +     stmt_vec_info stmt_vinfo
> > +       = vect_stmt_to_vectorize (loop_vinfo->lookup_stmt (stmt));
> > +     stmt = STMT_VINFO_STMT (stmt_vinfo);
> >       auto dr_ref = STMT_VINFO_DATA_REF (stmt_vinfo);
> >       if (!dr_ref)
> >         continue;
> > @@ -748,26 +750,16 @@ vect_analyze_early_break_dependences
> (loop_vec_info loop_vinfo)
> >          bounded by VF so accesses are within range.  We only need to check
> >          the reads since writes are moved to a safe place where if we get
> >          there we know they are safe to perform.  */
> > -     if (DR_IS_READ (dr_ref)
> > -         && !ref_within_array_bound (stmt, DR_REF (dr_ref)))
> > +     if (DR_IS_READ (dr_ref))
> >         {
> > -         if (STMT_VINFO_GATHER_SCATTER_P (stmt_vinfo)
> > -             || STMT_VINFO_STRIDED_P (stmt_vinfo))
> > -           {
> > -             const char *msg
> > -               = "early break not supported: cannot peel "
> > -                 "for alignment, vectorization would read out of "
> > -                 "bounds at %G";
> > -             return opt_result::failure_at (stmt, msg, stmt);
> > -           }
> > -
> > -         dr_vec_info *dr_info = STMT_VINFO_DR_INFO (stmt_vinfo);
> > -         dr_info->need_peeling_for_alignment = true;
> > +         dr_set_safe_speculative_read_required (stmt_vinfo, true);
> > +         bool inbounds = ref_within_array_bound (stmt, DR_REF (dr_ref));
> > +         DR_SCALAR_KNOWN_BOUNDS (STMT_VINFO_DR_INFO (stmt_vinfo))
> = inbounds;
> >
> >           if (dump_enabled_p ())
> >             dump_printf_loc (MSG_NOTE, vect_location,
> > -                            "marking DR (read) as needing peeling for "
> > -                            "alignment at %G", stmt);
> > +                            "marking DR (read) as possibly needing peeling 
> > "
> > +                            "for alignment at %G", stmt);
> >         }
> >
> >       if (DR_IS_READ (dr_ref))
> > @@ -1326,9 +1318,6 @@ vect_record_base_alignments (vec_info *vinfo)
> >     Compute the misalignment of the data reference DR_INFO when vectorizing
> >     with VECTYPE.
> >
> > -   RESULT is non-NULL iff VINFO is a loop_vec_info.  In that case, *RESULT 
> > will
> > -   be set appropriately on failure (but is otherwise left unchanged).
> > -
> >     Output:
> >     1. initialized misalignment info for DR_INFO
> >
> > @@ -1337,7 +1326,7 @@ vect_record_base_alignments (vec_info *vinfo)
> >
> >  static void
> >  vect_compute_data_ref_alignment (vec_info *vinfo, dr_vec_info *dr_info,
> > -                            tree vectype, opt_result *result = nullptr)
> > +                            tree vectype)
> >  {
> >    stmt_vec_info stmt_info = dr_info->stmt;
> >    vec_base_alignments *base_alignments = &vinfo->base_alignments;
> > @@ -1365,63 +1354,29 @@ vect_compute_data_ref_alignment (vec_info
> *vinfo, dr_vec_info *dr_info,
> >      = exact_div (targetm.vectorize.preferred_vector_alignment (vectype),
> >              BITS_PER_UNIT);
> >
> > -  /* If this DR needs peeling for alignment for correctness, we must
> > -     ensure the target alignment is a constant power-of-two multiple of the
> > -     amount read per vector iteration (overriding the above hook where
> > -     necessary).  */
> > -  if (dr_info->need_peeling_for_alignment)
> > +  if (loop_vinfo
> > +      && dr_safe_speculative_read_required (stmt_info))
> >      {
> > -      /* Vector size in bytes.  */
> > -      poly_uint64 safe_align = tree_to_poly_uint64 (TYPE_SIZE_UNIT 
> > (vectype));
> > -
> > -      /* We can only peel for loops, of course.  */
> > -      gcc_checking_assert (loop_vinfo);
> > -
> > -      /* Calculate the number of vectors read per vector iteration.  If
> > -    it is a power of two, multiply through to get the required
> > -    alignment in bytes.  Otherwise, fail analysis since alignment
> > -    peeling wouldn't work in such a case.  */
> > -      poly_uint64 num_scalars = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
> > +      poly_uint64 vf = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
> > +      auto vectype_size
> > +   = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (TREE_TYPE (vectype)));
> > +      poly_uint64 new_alignment = vf * vectype_size;
> > +      /* If we have a grouped access we require that the alignment be N * 
> > elem.  */
> >        if (STMT_VINFO_GROUPED_ACCESS (stmt_info))
> > -   num_scalars *= DR_GROUP_SIZE (stmt_info);
> > +   new_alignment *= DR_GROUP_SIZE (DR_GROUP_FIRST_ELEMENT
> (stmt_info));
> > -      auto num_vectors = vect_get_num_vectors (num_scalars, vectype);
> > -      if (!pow2p_hwi (num_vectors))
> > -   {
> > -     *result = opt_result::failure_at (vect_location,
> > -                                       "non-power-of-two num vectors %u "
> > -                                       "for DR needing peeling for "
> > -                                       "alignment at %G",
> > -                                       num_vectors, stmt_info->stmt);
> > -     return;
> > -   }
> > -
> > -      safe_align *= num_vectors;
> > -      if (maybe_gt (safe_align, 4096U))
> > -   {
> > -     pretty_printer pp;
> > -     pp_wide_integer (&pp, safe_align);
> > -     *result = opt_result::failure_at (vect_location,
> > -                                       "alignment required for correctness"
> > -                                       " (%s) may exceed page size",
> > -                                       pp_formatted_text (&pp));
> > -     return;
> > -   }
> > -
> > -      unsigned HOST_WIDE_INT multiple;
> > -      if (!constant_multiple_p (vector_alignment, safe_align, &multiple)
> > -     || !pow2p_hwi (multiple))
> > +      unsigned HOST_WIDE_INT target_alignment;
> > +      if (new_alignment.is_constant (&target_alignment)
> > +     && pow2p_hwi (target_alignment))
> >     {
> >       if (dump_enabled_p ())
> >         {
> >           dump_printf_loc (MSG_NOTE, vect_location,
> > -                          "forcing alignment for DR from preferred (");
> > -         dump_dec (MSG_NOTE, vector_alignment);
> > -         dump_printf (MSG_NOTE, ") to safe align (");
> > -         dump_dec (MSG_NOTE, safe_align);
> > -         dump_printf (MSG_NOTE, ") for stmt: %G", stmt_info->stmt);
> > +                          "alignment increased due to early break to ");
> > +         dump_dec (MSG_NOTE, new_alignment);
> > +         dump_printf (MSG_NOTE, " bytes.\n");
> >         }
> > -     vector_alignment = safe_align;
> > +     vector_alignment = target_alignment;
> >     }
> >      }
> >
> > @@ -2487,6 +2442,8 @@ vect_enhance_data_refs_alignment (loop_vec_info
> loop_vinfo)
> >        || !slpeel_can_duplicate_loop_p (loop, LOOP_VINFO_IV_EXIT 
> > (loop_vinfo),
> >                                    loop_preheader_edge (loop))
> >        || loop->inner
> > +      /* We don't currently maintaing the LCSSA for prologue peeled 
> > inversed
> > +    loops.  */
> >        || LOOP_VINFO_EARLY_BREAKS_VECT_PEELED (loop_vinfo))
> >      do_peeling = false;
> >
> > @@ -2950,12 +2907,9 @@ vect_analyze_data_refs_alignment (loop_vec_info
> loop_vinfo)
> >       if (STMT_VINFO_GROUPED_ACCESS (dr_info->stmt)
> >           && DR_GROUP_FIRST_ELEMENT (dr_info->stmt) != dr_info->stmt)
> >         continue;
> > -     opt_result res = opt_result::success ();
> > +
> >       vect_compute_data_ref_alignment (loop_vinfo, dr_info,
> > -                                      STMT_VINFO_VECTYPE (dr_info->stmt),
> > -                                      &res);
> > -     if (!res)
> > -       return res;
> > +                                      STMT_VINFO_VECTYPE (dr_info->stmt));
> >     }
> >      }
> >
> > @@ -7219,7 +7173,7 @@ vect_supportable_dr_alignment (vec_info *vinfo,
> dr_vec_info *dr_info,
> >
> >    if (misalignment == 0)
> >      return dr_aligned;
> > -  else if (dr_info->need_peeling_for_alignment)
> > +  else if (dr_safe_speculative_read_required(stmt_info))
> 
> space after dr_safe_speculative_read_required
> 
> Depending on vectorizable_load this might be a bit restrictive (it
> makes peeling do the magic, but we could check
> dr_safe_speculative_read_required there as well).  But it's OK for
> now at least.
> 
> >      return dr_unaligned_unsupported;
> >
> >    /* For now assume all conditional loads/stores support unaligned
> > diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
> > index
> 6bbb16beff2c627fca11a7403ba5ee3a5faa21c1..e0e5598babc7b119d408d8351
> 2ae8c6047d4924c 100644
> > --- a/gcc/tree-vect-stmts.cc
> > +++ b/gcc/tree-vect-stmts.cc
> > @@ -2597,6 +2597,165 @@ get_load_store_type (vec_info  *vinfo,
> stmt_vec_info stmt_info,
> >        return false;
> >      }
> >
> > +  /* If this DR needs alignment for correctness, we must ensure the target
> > +     alignment is a constant power-of-two multiple of the amount read per
> > +     vector iteration or force masking.  */
> > +  if (dr_safe_speculative_read_required (stmt_info))
> > +    {
> > +      /* We can only peel for loops, of course.  */
> > +      gcc_checking_assert (loop_vinfo);
> > +
> > +      /* Check if we support the operation if early breaks are needed.  
> > Here we
> > +    must ensure that we don't access any more than the scalar code would
> > +    have.  A masked operation would ensure this, so for these load types
> > +    force masking.  */
> > +      if (LOOP_VINFO_EARLY_BREAKS (loop_vinfo)
> > +     && (*memory_access_type == VMAT_GATHER_SCATTER
> > +         || *memory_access_type == VMAT_STRIDED_SLP))
> > +   {
> > +     if (dump_enabled_p ())
> > +       dump_printf_loc (MSG_NOTE, vect_location,
> > +                        "early break not supported: cannot peel for "
> > +                        "alignment. With non-contiguous memory
> vectorization"
> > +                        " could read out of bounds at %G ",
> > +                        STMT_VINFO_STMT (stmt_info));
> > +     LOOP_VINFO_MUST_USE_PARTIAL_VECTORS_P (loop_vinfo) = true;
> > +   }
> > +
> > +      /* Vector size in bytes.  */
> > +      poly_uint64 safe_align;
> > +      if (nunits.is_constant ())
> > +   safe_align = tree_to_poly_uint64 (TYPE_SIZE_UNIT (vectype));
> > +      else
> > +   safe_align = estimated_poly_value (LOOP_VINFO_VECT_FACTOR
> (loop_vinfo),
> > +                                      POLY_VALUE_MAX);
> > +
> > +      auto num_vectors = ncopies;
> 
> You can't rely on ncopies for SLP, so in practice you'll see
> num_vectors == 1 always (unless you force --param vect-force-slp=0).
> I'm not sure why you need this test given you have the target alignment
> check below?

Yeah for SLP it doesn't matter, but as you said the param still exists and I 
don't
think we've introduced any SLP only code yet have we?

If you prefer I can drop it. What I don't actually remember for the non-SLP case
is if the VF accounts for the ncopies growth as well? If so I agree this is 
completely
superfluous for SLP and non-SLP.

> 
> > +      if (!pow2p_hwi (num_vectors))
> > +   {
> > +     if (dump_enabled_p ())
> > +       dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> > +                        "non-power-of-two num vectors %u "
> > +                        "for DR needing peeling for "
> > +                        "alignment at %G",
> > +                        num_vectors, STMT_VINFO_STMT (stmt_info));
> > +     return false;
> > +   }
> > +
> > +      auto target_alignment
> > +   = DR_TARGET_ALIGNMENT (STMT_VINFO_DR_INFO (stmt_info));
> > +      unsigned HOST_WIDE_INT target_align;
> > +      bool inbounds
> > +   = DR_SCALAR_KNOWN_BOUNDS (STMT_VINFO_DR_INFO (stmt_info));
> > +
> > +      /* If the scalar loop is known to be in bounds, and we're using 
> > scalar
> > +    accesses then there's no need to check further.  */
> > +      if (inbounds
> > +     && *memory_access_type == VMAT_ELEMENTWISE)
> > +   {
> > +     *alignment_support_scheme = dr_aligned;
> > +     return true;
> > +   }
> > +
> > +      bool group_aligned = false;
> > +      if (target_alignment.is_constant (&target_align)
> > +     && nunits.is_constant ())
> > +   {
> > +     poly_uint64 vf = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
> > +     auto vectype_size
> > +       = TREE_INT_CST_LOW (TYPE_SIZE_UNIT (TREE_TYPE (vectype)));
> > +     poly_uint64 required_alignment = vf * vectype_size;
> > +     /* If we have a grouped access we require that the alignment be N * 
> > elem.
> */
> > +     if (STMT_VINFO_GROUPED_ACCESS (stmt_info))
> > +       required_alignment *=
> > +           DR_GROUP_SIZE (DR_GROUP_FIRST_ELEMENT (stmt_info));
> > +     if (maybe_ne (target_alignment, required_alignment))
> 
> Note ->target_alignment only holds if *alignment_support_scheme ==
> dr_aligned but you don't seem to test this?  It would be OK to
> have target_alignment be a multiple of required_alignment.
> 

ACK, will change.

> > +       {
> > +         if (dump_enabled_p ())
> > +           dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> > +                        "desired alignment %wu not met. Instead got %wu "
> > +                        "needed for DR alignment at %G",
> 
> 'needed' sounds odd, omit it?
> 
> > +                        required_alignment.to_constant (),
> > +                        target_align, STMT_VINFO_STMT (stmt_info));
> > +         return false;
> > +       }
> > +
> > +     if (!pow2p_hwi (target_align))
> > +       {
> > +         if (dump_enabled_p ())
> > +           dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> > +                        "non-power-of-two vector alignment %wd "
> > +                        "needed for DR alignment at %G",
> 
> likewise.
> 
> > +                        target_align, STMT_VINFO_STMT (stmt_info));
> > +         return false;
> > +       }
> > +     group_aligned = true;
> > +   }
> > +      else if (inbounds)
> 
> so you have those early outs (return false) above, but here is a fallback?
> Shouldn't this then be not an else if but
> 
>     if (!group_aligned && inbounds)
> 
> ?

Ack, so you mean that those cases could still be handled by partial vectors.
Hmm that's true.

> 
> > +   LOOP_VINFO_MUST_USE_PARTIAL_VECTORS_P (loop_vinfo) = true;
> > +      else
> 
> and this else if (!group_aligned)?
> 
> > +   return false;
> > +
> > +      /* Even if uneven group sizes are aligned on the first load, the 
> > second
> > +    iteration won't be.  As such reject non-power of 2 group sizes.  */
> 
> isn't this covered above?

Ack, the group_size * above on the power of two alignment check should cover it.

> 
> > +      if (STMT_VINFO_GROUPED_ACCESS (stmt_info))
> > +   {
> > +     auto group_size = DR_GROUP_SIZE (DR_GROUP_FIRST_ELEMENT
> (stmt_info));
> > +     if (!pow2p_hwi (group_size))
> > +       {
> > +         if (group_aligned || inbounds)
> > +           LOOP_VINFO_MUST_USE_PARTIAL_VECTORS_P (loop_vinfo) =
> true;
> > +         else
> > +           {
> > +             if (dump_enabled_p ())
> > +               dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> > +                        "early break not supported: uneven group size, "
> > +                        "vectorization could read out of bounds at %G ",
> > +                        STMT_VINFO_STMT (stmt_info));
> > +             return false;
> > +           }
> > +       }
> > +   }
> > +
> > +      safe_align *= num_vectors;
> > +      /* For VLA we have to insert a runtime check that the vector loads
> > +    per iterations don't exceed a page size.  For now we can use
> > +    POLY_VALUE_MAX as a proxy as we can't peel for VLA.  */
> 
> And this should be a check on required_alignment computed above,
> resulting in group_aligned = false but still handling it in the
> inbounds case?
> 

ACK, since if larger than a pagesize it can be handled with partial
loops for the inbound case. and I guess out of bound case should be
handled through partial vectors.

> > +      if (maybe_gt (safe_align, (unsigned)param_min_pagesize))
> > +   {
> > +     if (dump_enabled_p ())
> > +       {
> > +         dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> > +                          "alignment required for correctness (");
> > +         dump_dec (MSG_MISSED_OPTIMIZATION, safe_align);
> > +         dump_printf (MSG_NOTE, ") may exceed page size\n");
> > +       }
> > +     return false;
> > +   }
> > +
> > +      /* There are multiple loads that have a misalignment that we couldn't
> > +    align.  We would need LOOP_VINFO_MUST_USE_PARTIAL_VECTORS_P to
> > +    vectorize. */
> > +      if (!STMT_VINFO_GROUPED_ACCESS (stmt_info)
> > +     && *misalignment != 0)
> 
> that's probably the missing dr_aligned check?
> 
> So, what I'm confused about is the following: we set ->target_alignment
> (if possible) to sth that peeling can ensure the accesses will be
> aligned - this then results in dr_aligned.  Here we verify if the
> access is aligned and aligned enough.
> 
> Now as said above, that we end up with dr_unaligned_unsupported is
> off, so we probably shouldn't use that to indicate the higher
> desired alignment to the peeling code.
> 

This is because of cases like in 
/work/gcc/gcc/testsuite/gcc.dg/vect/vect-early-break_56.c

Where

  /* check results:  */
  for (i = 0; i < n; i++)
    {
      if (sa[i+7] != sb[i] + sc[i] || ia[i+3] != ib[i] + ic[i])
        abort ();
    }

Where there is no group loads, but sa and ia have different misalignments and
peeling can't do anything here as there's no way to peel them to a mutual 
alignment
(it's even not something we even try).

So this is to reject these cases. If we get to vectorizable_load with any 
misalignment
still set, it means we had multiple known misalignments which we can't 
vectorize.

So explicitly, these cases *won't* be dr_aligned but will be marked as requiring
alignment.

> > +   return false;
> > +
> > +      /* When using a group access the first element may be aligned but the
> > +    subsequent loads may not be.  For LOAD_LANES since the loads are based
> > +    on the first DR then all loads in the group are aligned.  For
> > +    non-LOAD_LANES this is not the case. In particular a load + blend when
> > +    there are gaps can have the non first loads issued unaligned, even
> > +    partially overlapping the memory of the first load in order to simplify
> > +    the blend.  This is what the x86_64 backend does for instance.  As
> > +    such only the first load in the group is aligned, the rest are not.  */
> > +      else if (STMT_VINFO_GROUPED_ACCESS (stmt_info)
> > +          && *misalignment != 0
> > +          && *memory_access_type != VMAT_LOAD_STORE_LANES)
> > +   *alignment_support_scheme = dr_unaligned_supported;
> 
> this looks definitely bogus, some targets cannot do unaligned accesses.
> 

This is because of cases like 
/work/gcc/gcc/testsuite/gcc.dg/vect/vect-early-break_26.c:

  for (int i = 2; i < 64; i+=2)
    if (b[i] != a[i] - a[i-2]
        || b[i+1] != a[i+1] - a[i-1])
      abort ();

Where we have a group load with a with a gap.  On x86_64 this results in two 
loads
+ a blend.  But the second load isn't aligned.

I guess as we put all the alignment requirements on the group leader, that 
perhaps
this code in get_load_store_type should be gated on

STMT_VINFO_GROUPED_ACCESS (stmt_info)
&& DR_GROUP_FIRST_ELEMENT (stmt_info) == stmt_info

?

Enforcing the alignment on every group member would be wrong I think since
that ends up higher overall alignment than they need.

> So besides these issues in get_load_store_type the change looks good now.
> 

Thanks for the reviews.

Tamar
> Richard.
> 
> > +      else
> > +   *alignment_support_scheme = dr_aligned;
> > +    }
> > +
> >    if (*alignment_support_scheme == dr_unaligned_unsupported)
> >      {
> >        if (dump_enabled_p ())
> > diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
> > index
> b0cb081cba0ae8b11fbfcfcb8c6d440ec451ccb5..97caf61b345735d297ec49fd6ca
> 64797435b46fc 100644
> > --- a/gcc/tree-vectorizer.h
> > +++ b/gcc/tree-vectorizer.h
> > @@ -1281,7 +1281,11 @@ public:
> >
> >    /* Set by early break vectorization when this DR needs peeling for 
> > alignment
> >       for correctness.  */
> > -  bool need_peeling_for_alignment;
> > +  bool safe_speculative_read_required;
> > +
> > +  /* Set by early break vectorization when this DR's scalar accesses are 
> > known
> > +     to be inbounds of a known bounds loop.  */
> > +  bool scalar_access_known_in_bounds;
> >
> >    tree base_decl;
> >
> > @@ -1997,6 +2001,35 @@ dr_target_alignment (dr_vec_info *dr_info)
> >    return dr_info->target_alignment;
> >  }
> >  #define DR_TARGET_ALIGNMENT(DR) dr_target_alignment (DR)
> > +#define DR_SCALAR_KNOWN_BOUNDS(DR) (DR)-
> >scalar_access_known_in_bounds
> > +
> > +/* Return if the stmt_vec_info requires peeling for alignment.  */
> > +inline bool
> > +dr_safe_speculative_read_required (stmt_vec_info stmt_info)
> > +{
> > +  dr_vec_info *dr_info;
> > +  if (STMT_VINFO_GROUPED_ACCESS (stmt_info))
> > +    dr_info = STMT_VINFO_DR_INFO (DR_GROUP_FIRST_ELEMENT (stmt_info));
> > +  else
> > +    dr_info = STMT_VINFO_DR_INFO (stmt_info);
> > +
> > +  return dr_info->safe_speculative_read_required;
> > +}
> > +
> > +/* Set the safe_speculative_read_required for the the stmt_vec_info, if 
> > group
> > +   access then set on the fist element otherwise set on DR directly.  */
> > +inline void
> > +dr_set_safe_speculative_read_required (stmt_vec_info stmt_info,
> > +                                  bool requires_alignment)
> > +{
> > +  dr_vec_info *dr_info;
> > +  if (STMT_VINFO_GROUPED_ACCESS (stmt_info))
> > +    dr_info = STMT_VINFO_DR_INFO (DR_GROUP_FIRST_ELEMENT (stmt_info));
> > +  else
> > +    dr_info = STMT_VINFO_DR_INFO (stmt_info);
> > +
> > +  dr_info->safe_speculative_read_required = requires_alignment;
> > +}
> >
> >  inline void
> >  set_dr_target_alignment (dr_vec_info *dr_info, poly_uint64 val)
> >
> >
> >
> 
> --
> Richard Biener <rguent...@suse.de>
> SUSE Software Solutions Germany GmbH,
> Frankenstrasse 146, 90461 Nuernberg, Germany;
> GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)

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