[LoopUnswitch] Don't remove instructions with side effects.

This fixes PR32818.

Differential Revision:  https://reviews.llvm.org/D32664

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301722 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/LoopUnswitch.cpp

@@ -1275,7 +1275,8 @@ static void ReplaceUsesOfWith(Instruction *I, Value *V,
   LPM->deleteSimpleAnalysisValue(I, L);
   RemoveFromWorklist(I, Worklist);
   I->replaceAllUsesWith(V);
-  I->eraseFromParent();
+  if (!I->mayHaveSideEffects())
+    I->eraseFromParent();
   ++NumSimplify;
 }
 

test/Transforms/LoopUnswitch/pr32818.ll

@@ -0,0 +1,19 @@
+; Check that the call doesn't get removed even if
+; it has no uses. It could have side-effects.
+; RUN: opt -loop-unswitch -S %s | FileCheck %s
+
+; CHECK-LABEL: @tinky
+define i32 @tinkywinky(i8 %patatino) {
+  %cmp1 = icmp slt i8 %patatino, 5
+  br label %body
+body:
+  %i = select i1 %cmp1, i8 6, i8 undef
+  br i1 true, label %body, label %end
+end:
+  %split = phi i8 [ %i, %body ]
+  %conv4 = sext i8 %split to i32
+; CHECK: tail call fastcc i32 @fn5(
+  %call = tail call fastcc i32 @fn5(i32 %conv4)
+  ret i32 0
+}
+declare fastcc i32 @fn5(i32 returned) unnamed_addr