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| author | Uros Bizjak <ubizjak@gmail.com> | 2021-04-29 22:02:00 +0200 |
|---|---|---|
| committer | Uros Bizjak <ubizjak@gmail.com> | 2021-04-29 22:03:06 +0200 |
| commit | 86403f4e6e5f72169147aca7e0d0b63e303ad5cd (patch) | |
| tree | 126a8a19c90472c45a96fb967146c23f7998d91b /libcpp | |
| parent | b24d8acbfffe30f40e280f11f23adac81b1e7f0c (diff) | |
| download | gcc-86403f4e6e5f72169147aca7e0d0b63e303ad5cd.zip gcc-86403f4e6e5f72169147aca7e0d0b63e303ad5cd.tar.gz gcc-86403f4e6e5f72169147aca7e0d0b63e303ad5cd.tar.bz2 | |
i386: Optimize carry flag comparisons a bit
In ix86_int_compare, opportunistically swap operands of GTU and LEU comparisons
to emit carry flag comparison, with the expectation that the comparison will
combine to *add<mode>3_carry_0 or *sub<mode>3_carry_0 insn pattern.
Do not use ix86_expand_carry_flag_compare because this function prefers
carry flag comparisons too much - it forces the constants into registers
and/or emits additional arithmetic instructions to convert simple
comparisons into carry flag comparisons - but simply swap operands to
convert GTU and LEU comparisons into GEU and LTU ones.
Also, change the insn predicates of *add<mode>3_carry_0 and
*sub<mode>3_carry_0 insn patterns to allow more combine opportunities
with memory operands.
2021-04-29 Uroš Bizjak <ubizjak@gmail.com>
gcc/
* config/i386/i386-expand.c (ix86_expand_int_compare):
Swap operands of GTU and LEU comparison to emit carry flag comparison.
* config/i386/i386.md (*add<mode>3_carry_0): Change insn
predicate to allow more combine opportunities with memory operands.
(*sub<mode>3_carry_0): Ditto.
Diffstat (limited to 'libcpp')
0 files changed, 0 insertions, 0 deletions