Hi!
The following patch handles VECTOR_TYPE_P CONSTRUCTORs in
count_nonzero_bytes, including handling them if they have some elements
non-constant.
If there are still some constant elements before it (in the range queried),
we derive info at least from those bytes and consider the rest as unknown.
The first 3 hunks just punt in IMHO problematic cases, the spaghetti code
considers byte_size 0 as unknown size, determine yourself, so if offset
is equal to exp size, there are 0 bytes to consider (so nothing useful
to determine), but using byte_size 0 would mean use any size.
Similarly, native_encode_expr uses int type for offset (and size), so
padding it offset larger than INT_MAX could be silent miscompilation.
I've guarded the test to just a couple of targets known to handle it,
because e.g. on ia32 without -msse forwprop1 seems to lower the CONSTRUCTOR
into 4 BIT_FIELD_REF stores and I haven't figured out on what exactly
that depends on (e.g. powerpc* is fine on any CPUs, even with -mno-altivec
-mno-vsx, even -m32).
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2024-11-30 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/117057
* tree-ssa-strlen.cc (strlen_pass::count_nonzero_bytes): Punt also
when byte_size is equal to offset or nchars. Punt if offset is bigger
than INT_MAX. Handle vector CONSTRUCTOR with some elements constant,
possibly followed by non-constant.
* gcc.dg/strlenopt-32.c: Remove xfail and vect_slp_v2qi_store_unalign
specific scan-tree-dump-times directive.
* gcc.dg/strlenopt-96.c: New test.
--- gcc/tree-ssa-strlen.cc.jj 2024-11-23 13:00:31.476982808 +0100
+++ gcc/tree-ssa-strlen.cc 2024-11-29 22:53:17.465837084 +0100
@@ -4629,7 +4629,7 @@ strlen_pass::count_nonzero_bytes (tree e
return false;
unsigned HOST_WIDE_INT byte_size = tree_to_uhwi (size);
- if (byte_size < offset)
+ if (byte_size <= offset)
return false;
nbytes = byte_size - offset;
@@ -4682,7 +4682,7 @@ strlen_pass::count_nonzero_bytes (tree e
if (TREE_CODE (exp) == STRING_CST)
{
unsigned nchars = TREE_STRING_LENGTH (exp);
- if (nchars < offset)
+ if (nchars <= offset)
return false;
if (!nbytes)
@@ -4700,7 +4700,7 @@ strlen_pass::count_nonzero_bytes (tree e
unsigned char buf[256];
if (!prep)
{
- if (CHAR_BIT != 8 || BITS_PER_UNIT != 8)
+ if (CHAR_BIT != 8 || BITS_PER_UNIT != 8 || offset > INT_MAX)
return false;
/* If the pointer to representation hasn't been set above
for STRING_CST point it at the buffer. */
@@ -4710,11 +4710,75 @@ strlen_pass::count_nonzero_bytes (tree e
unsigned repsize = native_encode_expr (exp, buf, sizeof buf, offset);
if (repsize < nbytes)
{
- /* This should only happen when REPSIZE is zero because EXP
- doesn't denote an object with a known initializer, except
- perhaps when the reference reads past its end. */
- lenrange[0] = 0;
- prep = NULL;
+ /* Handle vector { 0x12345678, 0x23003412, x_1(D), y_2(D) }
+ and similar cases. Even when not all the elements are constant,
+ we can perhaps figure out something from the constant ones
+ and assume the others can be anything. */
+ if (TREE_CODE (exp) == CONSTRUCTOR
+ && CONSTRUCTOR_NELTS (exp)
+ && VECTOR_TYPE_P (TREE_TYPE (exp))
+ && nbytes <= sizeof buf)
+ {
+ tree v0 = CONSTRUCTOR_ELT (exp, 0)->value;
+ unsigned HOST_WIDE_INT elt_sz
+ = int_size_in_bytes (TREE_TYPE (v0));
+ unsigned int i, s = 0;
+ tree v, idx;
+ FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (exp), i, idx, v)
+ {
+ if (idx
+ && (VECTOR_TYPE_P (TREE_TYPE (v0))
+ || !tree_fits_uhwi_p (idx)
+ || tree_to_uhwi (idx) != i))
+ {
+ s = 0;
+ break;
+ }
+ if ((i + 1) * elt_sz <= offset)
+ continue;
+ unsigned int o = 0;
+ if (i * elt_sz < offset)
+ o = offset % elt_sz;
+ repsize = native_encode_expr (v, buf + s,
+ sizeof (buf) - s, o);
+ if (repsize != elt_sz - o)
+ break;
+ s += repsize;
+ }
+ if (s != 0 && s < nbytes)
+ {
+ unsigned HOST_WIDE_INT n = strnlen (prep, s);
+ if (n < lenrange[0])
+ lenrange[0] = n;
+ if (lenrange[1] < n && n != s)
+ lenrange[1] = n;
+ if (lenrange[2] < nbytes)
+ lenrange[2] = nbytes;
+ /* We haven't processed all bytes, the rest are unknown.
+ So, clear NULTERM if none of the initial bytes are
+ zero, and clear ALLNUL and ALLNONNULL because we don't
+ know about the remaining bytes. */
+ if (n == s)
+ *nulterm = false;
+ *allnul = false;
+ *allnonnul = false;
+ return true;
+ }
+ else if (s != nbytes)
+ {
+ /* See below. */
+ lenrange[0] = 0;
+ prep = NULL;
+ }
+ }
+ else
+ {
+ /* This should only happen when REPSIZE is zero because EXP
+ doesn't denote an object with a known initializer, except
+ perhaps when the reference reads past its end. */
+ lenrange[0] = 0;
+ prep = NULL;
+ }
}
else if (!nbytes)
nbytes = repsize;
--- gcc/testsuite/gcc.dg/strlenopt-32.c.jj 2024-10-11 11:30:38.865389752
+0200
+++ gcc/testsuite/gcc.dg/strlenopt-32.c 2024-11-29 15:52:20.296109588 +0100
@@ -190,5 +190,4 @@ main ()
return 0;
}
-/* { dg-final { scan-tree-dump-times "strlen \\(" 0 "strlen1" { xfail
vect_slp_v2qi_store_unalign } } } */
-/* { dg-final { scan-tree-dump-times "strlen \\(" 2 "strlen1" { target
vect_slp_v2qi_store_unalign } } } */
+/* { dg-final { scan-tree-dump-times "strlen \\(" 0 "strlen1" } } */
--- gcc/testsuite/gcc.dg/strlenopt-96.c.jj 2024-11-29 15:50:37.233571779
+0100
+++ gcc/testsuite/gcc.dg/strlenopt-96.c 2024-11-30 01:45:29.638067059 +0100
@@ -0,0 +1,42 @@
+/* PR tree-optimization/117057 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-additional-options "-msse" { target { i?86-*-* x86_64-*-* } } } */
+/* { dg-final { scan-tree-dump-times "return \[0-9\]*;" 4 "optimized" { target
i?86-*-* x86_64-*-* aarch64*-*-* powerpc*-*-* } } } */
+
+#include "strlenopt.h"
+
+typedef unsigned int V __attribute__((vector_size (2 * sizeof (int))));
+typedef unsigned int W __attribute__((vector_size (4 * sizeof (int))));
+
+size_t
+foo (void)
+{
+ char a[64];
+ *(long long *) a = 0x12003456789abcdeULL;
+ return strlen (a);
+}
+
+size_t
+bar (void)
+{
+ char a[64];
+ *(V *) a = (V) { 0x12345678U, 0x9a00bcdeU };
+ return strlen (a);
+}
+
+size_t
+baz (unsigned int x)
+{
+ char a[64];
+ *(V *) a = (V) { 0x12005678U, x };
+ return strlen (a);
+}
+
+size_t
+qux (unsigned int x)
+{
+ char a[64];
+ *(W *)a = (W) { 0x12345678U, 0x9abcdef0U, 0x12005678U, x };
+ return strlen (a);
+}
Jakub
