On Thu, 12 Oct 2023, Richard Biener wrote:
> The following handles byte-aligned, power-of-two and byte-multiple
> sized BIT_FIELD_REF reads in SRA. In particular this should cover
> BIT_FIELD_REFs created by optimize_bit_field_compare.
>
> For gcc.dg/tree-ssa/ssa-dse-26.c we now SRA the BIT_FIELD_REF
> appearing there leading to more DSE, fully eliding the aggregates.
>
> This results in the same false positive -Wuninitialized as the
> older attempt to remove the folding from optimize_bit_field_compare,
> fixed by initializing part of the aggregate unconditionally.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu for all languages.
>
> Martin is on leave so I'll push this tomorrow unless the Fortran
> folks have objections.
Err, and I forgot that hunk. It's
diff --git a/gcc/fortran/trans-expr.cc b/gcc/fortran/trans-expr.cc
index 7beefa2e69c..1b8be081a17 100644
--- a/gcc/fortran/trans-expr.cc
+++ b/gcc/fortran/trans-expr.cc
@@ -12015,7 +12015,10 @@ gfc_trans_assignment_1 (gfc_expr * expr1, gfc_expr *
expr2, bool init_flag,
&& !is_runtime_conformable (expr1, expr2);
/* Only analyze the expressions for coarray properties, when in coarray-lib
- mode. */
+ mode. Avoid false-positive uninitialized diagnostics with initializing
+ the codimension flag unconditionally. */
+ lhs_caf_attr.codimension = false;
+ rhs_caf_attr.codimension = false;
if (flag_coarray == GFC_FCOARRAY_LIB)
{
lhs_caf_attr = gfc_caf_attr (expr1, false, &lhs_refs_comp);
> Thanks,
> Richard.
>
> PR tree-optimization/111779
> gcc/
> * tree-sra.cc (sra_handled_bf_read_p): New function.
> (build_access_from_expr_1): Handle some BIT_FIELD_REFs.
> (sra_modify_expr): Likewise.
> (make_fancy_name_1): Skip over BIT_FIELD_REF.
>
> gcc/fortran/
> * trans-expr.cc (gfc_trans_assignment_1): Initialize
> lhs_caf_attr and rhs_caf_attr codimension flag to avoid
> false positive -Wuninitialized.
>
> gcc/testsuite/
> * gcc.dg/tree-ssa/ssa-dse-26.c: Adjust for more DSE.
> * gcc.dg/vect/vect-pr111779.c: New testcase.
> ---
> gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-26.c | 4 +-
> gcc/testsuite/gcc.dg/vect/vect-pr111779.c | 56 ++++++++++++++++++++++
> gcc/tree-sra.cc | 24 ++++++++--
> 3 files changed, 79 insertions(+), 5 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/vect/vect-pr111779.c
>
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-26.c
> b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-26.c
> index e3c33f49ef6..43152de5616 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-26.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-26.c
> @@ -31,5 +31,5 @@ constraint_equal (struct constraint a, struct constraint b)
> && constraint_expr_equal (a.rhs, b.rhs);
> }
>
> -/* { dg-final { scan-tree-dump-times "Deleted dead store: x = " 1 "dse1" } }
> */
> -/* { dg-final { scan-tree-dump-times "Deleted dead store: y = " 1 "dse1" } }
> */
> +/* { dg-final { scan-tree-dump-times "Deleted dead store: x = " 2 "dse1" } }
> */
> +/* { dg-final { scan-tree-dump-times "Deleted dead store: y = " 2 "dse1" } }
> */
> diff --git a/gcc/testsuite/gcc.dg/vect/vect-pr111779.c
> b/gcc/testsuite/gcc.dg/vect/vect-pr111779.c
> new file mode 100644
> index 00000000000..79b72aebc78
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/vect-pr111779.c
> @@ -0,0 +1,56 @@
> +#include <stdbool.h>
> +#include "tree-vect.h"
> +
> +struct C
> +{
> + int c;
> + int d;
> + bool f :1;
> + float e;
> +};
> +
> +struct A
> +{
> + unsigned int a;
> + unsigned char c1, c2;
> + bool b1 : 1;
> + bool b2 : 1;
> + bool b3 : 1;
> + struct C b4;
> +};
> +
> +void __attribute__((noipa))
> +foo (const struct A * __restrict x, int y)
> +{
> + int s = 0, i = 0;
> + for (i = 0; i < y; ++i)
> + {
> + const struct A a = x[i];
> + s += a.b4.f ? 1 : 0;
> + }
> + if (s != 0)
> + __builtin_abort ();
> +}
> +
> +int
> +main ()
> +{
> + struct A x[100];
> + int i;
> +
> + check_vect ();
> +
> + __builtin_memset (x, -1, sizeof (x));
> +#pragma GCC novect
> + for (i = 0; i < 100; i++)
> + {
> + x[i].b1 = false;
> + x[i].b2 = false;
> + x[i].b3 = false;
> + x[i].b4.f = false;
> + }
> + foo (x, 100);
> + return 0;
> +}
> +
> +/* { dg-final { scan-tree-dump "LOOP VECTORIZED" "vect" { target vect_int }
> } } */
> diff --git a/gcc/tree-sra.cc b/gcc/tree-sra.cc
> index 56a8ba26135..24d0c20da6a 100644
> --- a/gcc/tree-sra.cc
> +++ b/gcc/tree-sra.cc
> @@ -1113,6 +1113,21 @@ disqualify_base_of_expr (tree t, const char *reason)
> disqualify_candidate (t, reason);
> }
>
> +/* Return true if the BIT_FIELD_REF read EXPR is handled by SRA. */
> +
> +static bool
> +sra_handled_bf_read_p (tree expr)
> +{
> + uint64_t size, offset;
> + if (bit_field_size (expr).is_constant (&size)
> + && bit_field_offset (expr).is_constant (&offset)
> + && size % BITS_PER_UNIT == 0
> + && offset % BITS_PER_UNIT == 0
> + && pow2p_hwi (size))
> + return true;
> + return false;
> +}
> +
> /* Scan expression EXPR and create access structures for all accesses to
> candidates for scalarization. Return the created access or NULL if none
> is
> created. */
> @@ -1123,7 +1138,8 @@ build_access_from_expr_1 (tree expr, gimple *stmt, bool
> write)
> struct access *ret = NULL;
> bool partial_ref;
>
> - if (TREE_CODE (expr) == BIT_FIELD_REF
> + if ((TREE_CODE (expr) == BIT_FIELD_REF
> + && (write || !sra_handled_bf_read_p (expr)))
> || TREE_CODE (expr) == IMAGPART_EXPR
> || TREE_CODE (expr) == REALPART_EXPR)
> {
> @@ -1170,6 +1186,7 @@ build_access_from_expr_1 (tree expr, gimple *stmt, bool
> write)
> case COMPONENT_REF:
> case ARRAY_REF:
> case ARRAY_RANGE_REF:
> + case BIT_FIELD_REF:
> ret = create_access (expr, stmt, write);
> break;
>
> @@ -1549,6 +1566,7 @@ make_fancy_name_1 (tree expr)
> obstack_grow (&name_obstack, buffer, strlen (buffer));
> break;
>
> + case BIT_FIELD_REF:
> case ADDR_EXPR:
> make_fancy_name_1 (TREE_OPERAND (expr, 0));
> break;
> @@ -1564,7 +1582,6 @@ make_fancy_name_1 (tree expr)
> }
> break;
>
> - case BIT_FIELD_REF:
> case REALPART_EXPR:
> case IMAGPART_EXPR:
> gcc_unreachable (); /* we treat these as scalars. */
> @@ -3769,7 +3786,8 @@ sra_modify_expr (tree *expr, gimple_stmt_iterator *gsi,
> bool write)
> tree type, bfr, orig_expr;
> bool partial_cplx_access = false;
>
> - if (TREE_CODE (*expr) == BIT_FIELD_REF)
> + if (TREE_CODE (*expr) == BIT_FIELD_REF
> + && (write || !sra_handled_bf_read_p (*expr)))
> {
> bfr = *expr;
> expr = &TREE_OPERAND (*expr, 0);
>
--
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)
