Add test case for add to sub transformation. NFC

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@355277 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/test/Transforms/InstCombine/add.ll b/test/Transforms/InstCombine/add.ll
index abf81a58c30fdcaecd6d7be1b91ce4803ddaed15..a6a305bd41bd9f74f9a4f042fc05eafe62202e33 100644 (file)
--- a/test/Transforms/InstCombine/add.ll
+++ b/test/Transforms/InstCombine/add.ll
@@ -947,3 +947,30 @@ define i32 @add_not_increment_commuted(i32 %A, i32 %B) {
   ret i32 %E
 }
 
+; E = (A + ~B) + 1 = A - B
+define i32 @add_to_sub(i32 %A, i32 %B) {
+; CHECK-LABEL: @add_to_sub(
+; CHECK-NEXT:    [[C:%.*]] = xor i32 [[B:%.*]], -1
+; CHECK-NEXT:    [[D:%.*]] = add i32 [[C]], [[A:%.*]]
+; CHECK-NEXT:    [[E:%.*]] = add i32 [[D]], 1
+; CHECK-NEXT:    ret i32 [[E]]
+;
+  %C = xor i32 %B, -1
+  %D = add i32 %A, %C
+  %E = add i32 %D, 1
+  ret i32 %E
+}
+
+; E = (~B + A) + 1 = A - B
+define i32 @add_to_sub2(i32 %A, i32 %B) {
+; CHECK-LABEL: @add_to_sub2(
+; CHECK-NEXT:    [[C:%.*]] = xor i32 [[B:%.*]], -1
+; CHECK-NEXT:    [[D:%.*]] = add i32 [[C]], [[A:%.*]]
+; CHECK-NEXT:    [[E:%.*]] = add i32 [[D]], 1
+; CHECK-NEXT:    ret i32 [[E]]
+;
+  %C = xor i32 %B, -1
+  %D = add i32 %C, %A
+  %E = add i32 %D, 1
+  ret i32 %E
+}