[ARM] ADD with a negative offset can become SUB for free

So model that directly in TTI::getIntImmCost().

llvm-svn: 281044

1 files changed, 17 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/ARM/immcost.ll b/llvm/test/CodeGen/ARM/immcost.ll
index 43a4989e6bd..1b05ffbfac9 100644
--- a/llvm/test/CodeGen/ARM/immcost.ll
+++ b/llvm/test/CodeGen/ARM/immcost.ll
@@ -71,3 +71,20 @@ true:
 ret:
   ret void
 }
+
+; CHECK: Function: test_add_neg
+; CHECK-NOT: Collect constant i32 -5
+define void @test_add_neg(i1 %cond, i32 %arg, i32 %arg2) {
+entry:
+  %a = add i32 %arg, -5
+  call void @g(i32 %a)
+  br i1 %cond, label %true, label %ret
+
+true:
+  %b = add i32 %arg2, -5
+  call void @g(i32 %b)
+  br label %ret
+
+ret:
+  ret void
+}