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| author | Roger Sayle <roger@nextmovesoftware.com> | 2022-06-27 07:44:49 +0100 |
|---|---|---|
| committer | Roger Sayle <roger@nextmovesoftware.com> | 2022-06-27 07:44:49 +0100 |
| commit | f3f73e86ec8613f176db3e52bbfbfbb9636cb714 (patch) | |
| tree | d1d5494a41fd8953a3de98c88875ad5875b484bc /gcc | |
| parent | 2ae7895416a7aa4fc9e7f9fa646dca1f51bdea56 (diff) | |
| download | gcc-f3f73e86ec8613f176db3e52bbfbfbb9636cb714.zip gcc-f3f73e86ec8613f176db3e52bbfbfbb9636cb714.tar.gz gcc-f3f73e86ec8613f176db3e52bbfbfbb9636cb714.tar.bz2 | |
[PATCH] PR tree-optimization/94026: Simplify (X>>8)&6 != 0 as X&1536 != 0.
This patch implements the missed optimization described in PR 94026,
where a the shift can be eliminated from the sequence of a shift,
followed by a bit-wise AND followed by an equality/inequality test.
Specifically, ((X << C1) & C2) cmp C3 into (X & (C2 >> C1)) cmp (C3 >> C1)
and likewise ((X >> C1) & C2) cmp C3 into (X & (C2 << C1)) cmp (C3 << C1)
where cmp is == or !=, and C1, C2 and C3 are integer constants.
The example in the subject line is taken from the hot function
self_atari from the Go program Leela (in SPEC CPU 2017).
2022-06-27 Roger Sayle <roger@nextmovesoftware.com>
gcc/ChangeLog
PR tree-optimization/94026
* match.pd (((X << C1) & C2) eq/ne C3): New simplification.
(((X >> C1) & C2) eq/ne C3): Likewise.
gcc/testsuite/ChangeLog
PR tree-optimization/94026
* gcc.dg/pr94026.c: New test case.
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/match.pd | 23 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.dg/pr94026.c | 21 |
2 files changed, 44 insertions, 0 deletions
diff --git a/gcc/match.pd b/gcc/match.pd index e486b4b..24cbbbb 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -3572,6 +3572,29 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) && wi::lshift (wi::to_wide (@0), cand) == wi::to_wide (@2)) (cmp @1 { build_int_cst (TREE_TYPE (@1), cand); })))))) +/* Fold ((X << C1) & C2) cmp C3 into (X & (C2 >> C1)) cmp (C3 >> C1) + ((X >> C1) & C2) cmp C3 into (X & (C2 << C1)) cmp (C3 << C1). */ +(for cmp (ne eq) + (simplify + (cmp (bit_and:s (lshift:s @0 INTEGER_CST@1) INTEGER_CST@2) INTEGER_CST@3) + (if (tree_fits_shwi_p (@1) + && tree_to_shwi (@1) > 0 + && tree_to_shwi (@1) < TYPE_PRECISION (TREE_TYPE (@0)) + && tree_to_shwi (@1) <= wi::ctz (wi::to_wide (@3))) + (with { wide_int c1 = wi::to_wide (@1); + wide_int c2 = wi::lrshift (wi::to_wide (@2), c1); + wide_int c3 = wi::lrshift (wi::to_wide (@3), c1); } + (cmp (bit_and @0 { wide_int_to_tree (TREE_TYPE (@0), c2); }) + { wide_int_to_tree (TREE_TYPE (@0), c3); })))) + (simplify + (cmp (bit_and:s (rshift:s @0 INTEGER_CST@1) INTEGER_CST@2) INTEGER_CST@3) + (if (tree_fits_shwi_p (@1) + && tree_to_shwi (@1) > 0 + && tree_to_shwi (@1) < TYPE_PRECISION (TREE_TYPE (@0)) + && tree_to_shwi (@1) <= wi::clz (wi::to_wide (@2)) + && tree_to_shwi (@1) <= wi::clz (wi::to_wide (@3))) + (cmp (bit_and @0 (lshift @2 @1)) (lshift @3 @1))))) + /* Fold (X << C1) & C2 into (X << C1) & (C2 | ((1 << C1) - 1)) (X >> C1) & C2 into (X >> C1) & (C2 | ~((type) -1 >> C1)) if the new mask might be further optimized. */ diff --git a/gcc/testsuite/gcc.dg/pr94026.c b/gcc/testsuite/gcc.dg/pr94026.c new file mode 100644 index 0000000..deb4efd --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr94026.c @@ -0,0 +1,21 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-optimized" } */ + +int f1(int x) { return ((x >> 8) & 6) != 0; } +int f2(int x) { return ((x << 2) & 24) != 0; } +int f3(unsigned x) { return ((x << 2) & 15) != 0; } +int f4(unsigned x) { return ((x >> 2) & 14) != 0; } + +int fifth (int c) +{ + int a = (c >> 8) & 7; + + if (a >= 2) { + return 1; + } else { + return 0; + } +} +/* { dg-final { scan-tree-dump-not " << " "optimized" } } */ +/* { dg-final { scan-tree-dump-not " >> " "optimized" } } */ + |