From: Owen Anderson <resistor@mac.com>
Date: Wed, 15 Dec 2010 00:55:35 +0000 (+0000)
Subject: Fix PR8790, another instance where unreachable code can cause instruction simplificat... 
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=86e8a700f516e8993417fb57d5386614b35c775d;p=oota-llvm.git

Fix PR8790, another instance where unreachable code can cause instruction simplification to fail,
this case involve a select that simplifies to itself.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121817 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
index f364375ebd2..be12973b645 100644
--- a/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ b/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -73,7 +73,12 @@ bool CorrelatedValuePropagation::processSelect(SelectInst *S) {
   ConstantInt *CI = dyn_cast<ConstantInt>(C);
   if (!CI) return false;
 
-  S->replaceAllUsesWith(S->getOperand(CI->isOne() ? 1 : 2));
+  Value *ReplaceWith = S->getOperand(1);
+  Value *Other = S->getOperand(2);
+  if (!CI->isOne()) std::swap(ReplaceWith, Other);
+  if (ReplaceWith == S) ReplaceWith = UndefValue::get(S->getType());
+
+  S->replaceAllUsesWith(ReplaceWith);
   S->eraseFromParent();
 
   ++NumSelects;
diff --git a/test/Transforms/CorrelatedValuePropagation/crash.ll b/test/Transforms/CorrelatedValuePropagation/crash.ll
index 8636788511e..80c43d0f1da 100644
--- a/test/Transforms/CorrelatedValuePropagation/crash.ll
+++ b/test/Transforms/CorrelatedValuePropagation/crash.ll
@@ -18,3 +18,20 @@ for.cond.us.us:                                   ; preds = %for.cond.us.us
 for.end:                                          ; preds = %for.cond.us, %for.cond.us.us, %entry
   ret void
 }
+
+; PR 8790
+define void @test2() nounwind ssp {
+entry:
+  br label %func_29.exit
+
+sdf.exit.i:
+  %l_44.1.mux.i = select i1 %tobool5.not.i, i8 %l_44.1.mux.i, i8 1
+  br label %srf.exit.i
+
+srf.exit.i:
+  %tobool5.not.i = icmp ne i8 undef, 0
+  br i1 %tobool5.not.i, label %sdf.exit.i, label %func_29.exit
+
+func_29.exit:
+  ret void
+}