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| author | Jakub Jelinek <jakub@redhat.com> | 2009-11-03 23:36:39 +0100 |
|---|---|---|
| committer | Jakub Jelinek <jakub@gcc.gnu.org> | 2009-11-03 23:36:39 +0100 |
| commit | 24d179b4c7717ceeceef16166064bd4a3933cb11 (patch) | |
| tree | 219b8371e4eb10703f1ef240e27ca85c4e4861a9 /gcc/rtlanal.c | |
| parent | 0b94d8b285da86f4e68c396a285a2846df3bdff7 (diff) | |
| download | gcc-24d179b4c7717ceeceef16166064bd4a3933cb11.zip gcc-24d179b4c7717ceeceef16166064bd4a3933cb11.tar.gz gcc-24d179b4c7717ceeceef16166064bd4a3933cb11.tar.bz2 | |
re PR rtl-optimization/41917 (Strange athrithmetic result with -O3)
PR rtl-optimization/41917
* rtlanal.c (num_sign_bit_copies1) <case UMOD>: If sign bit of second
operand isn't known to be 0, return 1.
* gcc.c-torture/execute/pr41917.c: New test.
From-SVN: r153874
Diffstat (limited to 'gcc/rtlanal.c')
| -rw-r--r-- | gcc/rtlanal.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/gcc/rtlanal.c b/gcc/rtlanal.c index d14bbe5..120d37a 100644 --- a/gcc/rtlanal.c +++ b/gcc/rtlanal.c @@ -4517,8 +4517,16 @@ num_sign_bit_copies1 (const_rtx x, enum machine_mode mode, const_rtx known_x, known_x, known_mode, known_ret); case UMOD: - /* The result must be <= the second operand. */ - return cached_num_sign_bit_copies (XEXP (x, 1), mode, + /* The result must be <= the second operand. If the second operand + has (or just might have) the high bit set, we know nothing about + the number of sign bit copies. */ + if (bitwidth > HOST_BITS_PER_WIDE_INT) + return 1; + else if ((nonzero_bits (XEXP (x, 1), mode) + & ((HOST_WIDE_INT) 1 << (bitwidth - 1))) != 0) + return 1; + else + return cached_num_sign_bit_copies (XEXP (x, 1), mode, known_x, known_mode, known_ret); case DIV: |