Revert "[InstCombine] Don't miscompile safe increment idiom"

This is breaking a lot of build bots and is causing very long-running
compiles (infinite loops)?

Likely, we shouldn't return nullptr?

llvm-svn: 239139

1 files changed, 3 insertions, 21 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 4dec1542495..d2fbcdd3991 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -292,28 +292,10 @@ static Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
 
   // If this is a binary operator, try to simplify it with the replaced op.
   if (BinaryOperator *B = dyn_cast<BinaryOperator>(I)) {
-    Value *Simplified = nullptr;
     if (B->getOperand(0) == Op)
-      Simplified =
-          SimplifyBinOp(B->getOpcode(), RepOp, B->getOperand(1), DL, TLI);
-    if (!Simplified && B->getOperand(1) == Op)
-      Simplified =
-          SimplifyBinOp(B->getOpcode(), B->getOperand(0), RepOp, DL, TLI);
-    if (Simplified) {
-      // Consider:
-      //   %cmp = icmp eq i32 %x, 2147483647
-      //   %add = add nsw i32 %x, 1
-      //   %sel = select i1 %cmp, i32 -2147483648, i32 %add
-      //
-      // We can't replace %sel with %add unless we strip away the flags.
-      if (isa<OverflowingBinaryOperator>(B)) {
-        B->setHasNoSignedWrap(false);
-        B->setHasNoUnsignedWrap(false);
-      }
-      if (isa<PossiblyExactOperator>(B))
-        B->setIsExact(false);
-    }
-    return Simplified;
+      return SimplifyBinOp(B->getOpcode(), RepOp, B->getOperand(1), DL, TLI);
+    if (B->getOperand(1) == Op)
+      return SimplifyBinOp(B->getOpcode(), B->getOperand(0), RepOp, DL, TLI);
   }
 
   // Same for CmpInsts.