DAGCombine add (sext i1), X into sub X, (zext i1) if sext from i1 is illegal. The latter usually compiles into smaller code.
example code:
unsigned foo(unsigned x, unsigned y) {
if (x != 0) y--;
return y;
}
before:
_foo: ## @foo
cmpl $1, 4(%esp) ## encoding: [0x83,0x7c,0x24,0x04,0x01]
sbbl %eax, %eax ## encoding: [0x19,0xc0]
notl %eax ## encoding: [0xf7,0xd0]
addl 8(%esp), %eax ## encoding: [0x03,0x44,0x24,0x08]
ret ## encoding: [0xc3]
after:
_foo: ## @foo
cmpl $1, 4(%esp) ## encoding: [0x83,0x7c,0x24,0x04,0x01]
movl 8(%esp), %eax ## encoding: [0x8b,0x44,0x24,0x08]
adcl $-1, %eax ## encoding: [0x83,0xd0,0xff]
ret ## encoding: [0xc3]
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122455 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/CodeGen/X86/add.ll b/test/CodeGen/X86/add.ll
index d6e99ee..3ec5358 100644
--- a/test/CodeGen/X86/add.ll
+++ b/test/CodeGen/X86/add.ll
@@ -120,3 +120,15 @@
; X64: addq
; X64-NEXT: sbbq
; X64-NEXT: testb
+
+define i32 @test9(i32 %x, i32 %y) nounwind readnone {
+ %cmp = icmp eq i32 %x, 10
+ %sub = sext i1 %cmp to i32
+ %cond = add i32 %sub, %y
+ ret i32 %cond
+; X64: test9:
+; X64: cmpl $10
+; X64: sete
+; X64: subl
+; X64: ret
+}