diff options
| -rw-r--r-- | lib/Target/X86/README.txt | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt index 046d35ce5b..5967fd55c0 100644 --- a/lib/Target/X86/README.txt +++ b/lib/Target/X86/README.txt @@ -1952,3 +1952,26 @@ fact these instructions are identical to the non-lock versions. We need a way to add target specific information to target nodes and have this information carried over to machine instructions. Asm printer (or JIT) can use this information to add the "lock" prefix. + +//===---------------------------------------------------------------------===// + +int func(int a, int b) { if (a & 0x80) b |= 0x80; else b &= 0x80; return b; } + +Current: + + movb %sil, %al + andb $-128, %sil + orb $-128, %al + testb %dil, %dil + js LBB1_2 + movb %sil, %al +LBB1_2: + movsbl %al, %eax + +Better: + movl %esi, %eax + orl $-128, %eax + andl $-128, %esi + testb %dil, %dil + cmovns %esi, %eax + movsbl %al,%eax |