diff options
| author | Roger Sayle <roger@nextmovesoftware.com> | 2022-12-28 19:27:52 +0000 |
|---|---|---|
| committer | Roger Sayle <roger@nextmovesoftware.com> | 2022-12-28 19:27:52 +0000 |
| commit | 38b649ec16c965733aab9efa6bf61faae3485d92 (patch) | |
| tree | 1de2ca386624ccfb3824eec791dff1a5375ee333 /gcc/config | |
| parent | d898a17b927531bbc0de7ad0991dc3c96915d67d (diff) | |
| download | gcc-38b649ec16c965733aab9efa6bf61faae3485d92.zip gcc-38b649ec16c965733aab9efa6bf61faae3485d92.tar.gz gcc-38b649ec16c965733aab9efa6bf61faae3485d92.tar.bz2 | |
Use ix86_expand_clear in ix86_split_ashl.
This patch is a one line change, to call ix86_expand_clear instead of
emit_move_insn with const0_rtx in ix86_split_ashl, allowing the backend
to use an xor instruction to clear a register if appropriate.
The effect is demonstrated with the following function.
__int128 foo(__int128 x, unsigned long long b) {
return ((__int128)b << 72) + x;
}
previously with -O2, GCC would generate
foo: movl $0, %eax
salq $8, %rdx
addq %rdi, %rax
adcq %rsi, %rdx
ret
with this patch, it now generates
foo: xorl %eax, %eax
salq $8, %rdx
addq %rdi, %rax
adcq %rsi, %rdx
ret
2022-12-28 Roger Sayle <roger@nextmovesoftware.com>
gcc/ChangeLog
* config/i386/i386-expand.cc (ix86_split_ashl): Call
ix86_expand_clear to generate an xor instruction.
gcc/testsuite/ChangeLog
* gcc.target/i386/ashlti3-1.c: New test case.
Diffstat (limited to 'gcc/config')
| -rw-r--r-- | gcc/config/i386/i386-expand.cc | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/gcc/config/i386/i386-expand.cc b/gcc/config/i386/i386-expand.cc index b6cc76d..3eddbc9 100644 --- a/gcc/config/i386/i386-expand.cc +++ b/gcc/config/i386/i386-expand.cc @@ -6211,7 +6211,7 @@ ix86_split_ashl (rtx *operands, rtx scratch, machine_mode mode) if (count >= half_width) { emit_move_insn (high[0], low[1]); - emit_move_insn (low[0], const0_rtx); + ix86_expand_clear (low[0]); if (count > half_width) ix86_expand_ashl_const (high[0], count - half_width, mode); |