This patch changes the lowering of 64-bit integer compares on 32-bit x86 to be more efficient.
Example:
define i32 @test_slt(i64 %a, i64 %b) {
entry:
%cmp = icmp slt i64 %a, %b
br i1 %cmp, label %bb1, label %bb2
bb1:
ret i32 1
bb2:
ret i32 2
}Before this patch:
test_slt:
movl 4(%esp), %eax
movl 8(%esp), %ecx
cmpl 12(%esp), %eax
setae %al
cmpl 16(%esp), %ecx
setge %cl
je .LBB2_2
movb %cl, %al
.LBB2_2:
testb %al, %al
jne .LBB2_4
movl $1, %eax
retl
.LBB2_4:
movl $2, %eax
retlAfter this patch:
test_slt:
movl 4(%esp), %eax
movl 8(%esp), %ecx
cmpl 12(%esp), %eax
sbbl 16(%esp), %ecx
jge .LBB1_2
movl $1, %eax
retl
.LBB1_2:
movl $2, %eax
retlOn a 32-bit Clang bootstrap, this results in 19 KB binary size reduction.