diff options
| -rw-r--r-- | lib/Target/X86/README.txt | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt index eda9314..fccddc7 100644 --- a/lib/Target/X86/README.txt +++ b/lib/Target/X86/README.txt @@ -1687,3 +1687,41 @@ doload64: ret //===---------------------------------------------------------------------===// + +We compile this function: + +define i32 @foo(i32 %a, i32 %b, i32 %c, i8 zeroext %d) nounwind { +entry: + %tmp2 = icmp eq i8 %d, 0 ; <i1> [#uses=1] + br i1 %tmp2, label %bb7, label %bb + +bb: ; preds = %entry + %tmp6 = add i32 %b, %a ; <i32> [#uses=1] + ret i32 %tmp6 + +bb7: ; preds = %entry + %tmp10 = sub i32 %a, %c ; <i32> [#uses=1] + ret i32 %tmp10 +} + +to: + +_foo: + cmpb $0, 16(%esp) + movl 12(%esp), %ecx + movl 8(%esp), %eax + movl 4(%esp), %edx + je LBB1_2 # bb7 +LBB1_1: # bb + addl %edx, %eax + ret +LBB1_2: # bb7 + movl %edx, %eax + subl %ecx, %eax + ret + +The coallescer could coallesce "edx" with "eax" to avoid the movl in LBB1_2 +if it commuted the addl in LBB1_1. + +//===---------------------------------------------------------------------===// + |