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| author | Richard Biener <rguenther@suse.de> | 2025-05-06 08:36:01 +0200 |
|---|---|---|
| committer | Richard Biener <rguenth@gcc.gnu.org> | 2025-05-06 11:17:44 +0200 |
| commit | 5e363ffefaceb9ff8fdeeead247c8337538e01db (patch) | |
| tree | e2b82902fe559610114d1d895b26e62734a1ca68 | |
| parent | 16e301adf7b653c72d5c3cae1c7287877f3f20ff (diff) | |
| download | gcc-5e363ffefaceb9ff8fdeeead247c8337538e01db.zip gcc-5e363ffefaceb9ff8fdeeead247c8337538e01db.tar.gz gcc-5e363ffefaceb9ff8fdeeead247c8337538e01db.tar.bz2 | |
tree-optimization/120031 - CTZ pattern matching fails a case
This PR is about the pattern matching in tree-ssa-forwprop.cc not
working for the fallback implementation in ZSTD which uses a cast
aroud the negation of the value to be tested. There's a pattern
eliding casts in (T')-(T)x already but that only covered an
inner widening conversion. The following extends this to other
conversions given the negation will then be carried out in an
unsigned type.
PR tree-optimization/120031
* match.pd ((nop_outer_cast)-(inner_cast)var -> -(outer_cast)(var)):
Allow inner conversions that are not widenings when the outer
type is unsigned.
* gcc.target/i386/pr120031.c: New testcase.
| -rw-r--r-- | gcc/match.pd | 9 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.target/i386/pr120031.c | 15 |
2 files changed, 20 insertions, 4 deletions
diff --git a/gcc/match.pd b/gcc/match.pd index a150de5..ab496d9 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -1123,9 +1123,9 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) #endif /* (nop_outer_cast)-(inner_cast)var -> -(outer_cast)(var) - if var is smaller in precision. - This is always safe for both doing the negative in signed or unsigned - as the value for undefined will not show up. + If var is smaller in precision this is always safe for both doing + the negative in signed or unsigned as the value for undefined will not + show up. Else it is safe if the negation is done in an unsigned type. Note the outer cast cannot be a boolean type as the only valid values are 0,-1/1 (depending on the signedness of the boolean) and the negative is there to get the correct value. */ @@ -1133,7 +1133,8 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (convert (negate:s@1 (convert:s @0))) (if (INTEGRAL_TYPE_P (type) && tree_nop_conversion_p (type, TREE_TYPE (@1)) - && TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0)) + && (TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0)) + || TYPE_UNSIGNED (type)) && TREE_CODE (type) != BOOLEAN_TYPE) (negate (convert @0)))) diff --git a/gcc/testsuite/gcc.target/i386/pr120031.c b/gcc/testsuite/gcc.target/i386/pr120031.c new file mode 100644 index 0000000..e329cbc2 --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr120031.c @@ -0,0 +1,15 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -mbmi" } */ + +unsigned int +ZSTD_countTrailingZeros32_fallback (unsigned int val) +{ + static const unsigned int DeBruijn[32] + = { 0, 1, 28, 2, 29, 14, 24, 3, + 30, 22, 20, 15, 25, 17, 4, 8, + 31, 27, 13, 23, 21, 19, 16, 7, + 26, 12, 18, 6, 11, 5, 10, 9}; + return DeBruijn[((unsigned int) ((val & -(int) val) * 0x077CB531U)) >> 27]; +} + +/* { dg-final { scan-assembler "tzcnt" } } */ |