diff options
Diffstat (limited to 'gcc/config/i386/i386.cc')
| -rw-r--r-- | gcc/config/i386/i386.cc | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc index 587b2bd..6b6febc 100644 --- a/gcc/config/i386/i386.cc +++ b/gcc/config/i386/i386.cc @@ -598,6 +598,20 @@ ix86_canonicalize_comparison (int *code, rtx *op0, rtx *op1, } } + /* SUB (a, b) underflows precisely when a < b. Convert + (compare (minus (a b)) a) to (compare (a b)) + to match *sub<mode>_3 pattern. */ + if (!op0_preserve_value + && (*code == GTU || *code == LEU) + && GET_CODE (*op0) == MINUS + && rtx_equal_p (XEXP (*op0, 0), *op1)) + { + *op1 = XEXP (*op0, 1); + *op0 = XEXP (*op0, 0); + *code = (int) swap_condition ((enum rtx_code) *code); + return; + } + /* Swap operands of GTU comparison to canonicalize addcarry/subborrow comparison. */ if (!op0_preserve_value |