diff options
| -rw-r--r-- | gcc/match.pd | 11 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.dg/tree-ssa/bittest.c | 27 |
2 files changed, 38 insertions, 0 deletions
diff --git a/gcc/match.pd b/gcc/match.pd index 71cf6f9..cdab5e5 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -3441,6 +3441,17 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (bit_and (convert (shift:shift_type (convert @3) @1)) { newmaskt; }) (bit_and @4 { newmaskt; }))))))))))))) +/* ((1 << n) & M) != 0 -> n == log2 (M) */ +(for cmp (ne eq) + icmp (eq ne) + (simplify + (cmp + (bit_and + (nop_convert? (lshift integer_onep @0)) integer_pow2p@1) integer_zerop) + (if (INTEGRAL_TYPE_P (TREE_TYPE (@0))) + (icmp @0 { wide_int_to_tree (TREE_TYPE (@0), + wi::exact_log2 (wi::to_wide (@1))); })))) + /* Fold (X {&,^,|} C2) << C1 into (X << C1) {&,^,|} (C2 << C1) (X {&,^,|} C2) >> C1 into (X >> C1) & (C2 >> C1). */ (for shift (lshift rshift) diff --git a/gcc/testsuite/gcc.dg/tree-ssa/bittest.c b/gcc/testsuite/gcc.dg/tree-ssa/bittest.c new file mode 100644 index 0000000..7d712ca --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/bittest.c @@ -0,0 +1,27 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-optimized" } */ + + +void bar (void); + +void +foo(unsigned int abc123) +{ + unsigned int xyzpdq = (1 << abc123); + if ((xyzpdq & 0x800) != 0) + bar(); +} + +void +baz(unsigned int abc123) +{ + unsigned int xyzpdq = (1 << abc123); + if ((xyzpdq & 0x800) == 0) + bar(); +} + +/* What we want to verify is that the bit test against xyzpdq is + replaced with a test against abc123 which avoids the shifting + and bit ops. */ +/* { dg-final { scan-tree-dump-not "xyzpdq" "optimized"} } */ +/* { dg-final { scan-tree-dump-times "if .abc123" 2 "optimized"} } */ |