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| author | Jakub Jelinek <jakub@redhat.com> | 2020-05-08 09:33:55 +0200 |
|---|---|---|
| committer | Jakub Jelinek <jakub@redhat.com> | 2020-05-08 09:33:55 +0200 |
| commit | df569f7da567af4996821dc0a1871eec79957d04 (patch) | |
| tree | cc4ced8f3fc3149413fca20171fb9bedf899abed /gcc | |
| parent | ff33680165346cb291667f38dd2e9f25a74cc3c3 (diff) | |
| download | gcc-df569f7da567af4996821dc0a1871eec79957d04.zip gcc-df569f7da567af4996821dc0a1871eec79957d04.tar.gz gcc-df569f7da567af4996821dc0a1871eec79957d04.tar.bz2 | |
match.pd: Optimize ffs of known non-zero arg into ctz + 1 [PR94956]
The ffs expanders on several targets (x86, ia64, aarch64 at least)
emit a conditional move or similar code to handle the case when the
argument is 0, which makes the code longer.
If we know from VRP that the argument will not be zero, we can (if the
target has also an ctz expander) just use ctz which is undefined at zero
and thus the expander doesn't need to deal with that.
2020-05-08 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/94956
* match.pd (FFS): Optimize __builtin_ffs* of non-zero argument into
__builtin_ctz* + 1 if direct IFN_CTZ is supported.
* gcc.target/i386/pr94956.c: New test.
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 4 | ||||
| -rw-r--r-- | gcc/match.pd | 10 | ||||
| -rw-r--r-- | gcc/testsuite/ChangeLog | 3 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.target/i386/pr94956.c | 28 |
4 files changed, 45 insertions, 0 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index eb4924a..5bad3ff 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,5 +1,9 @@ 2020-05-08 Jakub Jelinek <jakub@redhat.com> + PR tree-optimization/94956 + * match.pd (FFS): Optimize __builtin_ffs* of non-zero argument into + __builtin_ctz* + 1 if direct IFN_CTZ is supported. + PR tree-optimization/94913 * match.pd (A - B + -1 >= A to B >= A): New simplification. (A - B > A to A < B): Don't test TYPE_OVERFLOW_WRAPS which is always diff --git a/gcc/match.pd b/gcc/match.pd index cfe9697..892df1e 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -5986,6 +5986,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) && direct_internal_fn_supported_p (IFN_POPCOUNT, type, OPTIMIZE_FOR_BOTH)) (convert (IFN_POPCOUNT:type @0))))) + +/* __builtin_ffs needs to deal on many targets with the possible zero + argument. If we know the argument is always non-zero, __builtin_ctz + 1 + should lead to better code. */ +(simplify + (FFS tree_expr_nonzero_p@0) + (if (INTEGRAL_TYPE_P (TREE_TYPE (@0)) + && direct_internal_fn_supported_p (IFN_CTZ, TREE_TYPE (@0), + OPTIMIZE_FOR_SPEED)) + (plus (CTZ:type @0) { build_one_cst (type); }))) #endif /* Simplify: diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 43e226e..e8c54c7 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,5 +1,8 @@ 2020-05-08 Jakub Jelinek <jakub@redhat.com> + PR tree-optimization/94956 + * gcc.target/i386/pr94956.c: New test. + PR tree-optimization/94913 * gcc.dg/tree-ssa/pr94913.c: New test. diff --git a/gcc/testsuite/gcc.target/i386/pr94956.c b/gcc/testsuite/gcc.target/i386/pr94956.c new file mode 100644 index 0000000..cc27b45 --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/pr94956.c @@ -0,0 +1,28 @@ +/* PR tree-optimization/94956 */ +/* { dg-do compile } */ +/* { dg-options "-O2" } */ +/* { dg-final { scan-assembler-not "\tcmovne\t" } } */ +/* { dg-final { scan-assembler-not "\tsete\t" } } */ + +int +foo (unsigned x) +{ + if (x == 0) __builtin_unreachable (); + return __builtin_ffs (x) - 1; +} + +int +bar (unsigned long x) +{ + if (x == 0) __builtin_unreachable (); + return __builtin_ffsl (x) - 1; +} + +#ifdef __x86_64__ +int +baz (unsigned long long x) +{ + if (x == 0) __builtin_unreachable (); + return __builtin_ffsll (x) - 1; +} +#endif |