Nick Lewycky's patch.

While hosting instruction check PHI node.

llvm-svn: 57025

2 files changed, 37 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 604a7173845..7f4133630d8 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1051,7 +1051,7 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
   BasicBlock::iterator InsertPos = BI;
   if (InsertPos != BIParent->begin()) 
     --InsertPos;
-  if (InsertPos == BrCond) {
+  if (InsertPos == BrCond && !isa<PHINode>(BrCond)) {
     SmallPtrSet<Instruction *, 4> BB1Insns;
     for(BasicBlock::iterator BB1I = BB1->begin(), BB1E = BB1->end(); 
         BB1I != BB1E; ++BB1I) 
diff --git a/llvm/test/Transforms/SimplifyCFG/2008-10-03-SpeculativelyExecuteBeforePHI.ll b/llvm/test/Transforms/SimplifyCFG/2008-10-03-SpeculativelyExecuteBeforePHI.ll
new file mode 100644
index 00000000000..a061a82954b
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/2008-10-03-SpeculativelyExecuteBeforePHI.ll
@@ -0,0 +1,36 @@
+; RUN: llvm-as < %s | opt -simplifycfg
+; PR2855
+
+define i32 @_Z1fPii(i32* %b, i32 %f) nounwind {
+entry:
+	br label %bb
+
+bb:		; preds = %bb9, %bb7, %bb, %entry
+	%__c2.2 = phi i32 [ undef, %entry ], [ %__c2.1, %bb7 ], [ %__c2.1, %bb9 ]		; <i32> [#uses=2]
+	%s.0 = phi i32 [ 0, %entry ], [ 0, %bb7 ], [ %2, %bb9 ]		; <i32> [#uses=1]
+	br label %bb1
+
+bb1:		; preds = %bb
+	%0 = icmp slt i32 0, %f		; <i1> [#uses=1]
+	br i1 %0, label %bb3, label %bb6
+
+bb3:		; preds = %bb1
+	%1 = icmp eq i32 0, 0		; <i1> [#uses=1]
+	br i1 %1, label %bb6, label %bb5
+
+bb5:		; preds = %bb3
+	br label %bb7
+
+bb6:		; preds = %bb3, %bb1
+	%__c2.0 = phi i32 [ 0, %bb3 ], [ %__c2.2, %bb1 ]		; <i32> [#uses=1]
+	br label %bb7
+
+bb7:		; preds = %bb6, %bb5
+	%__c2.1 = phi i32 [ 0, %bb5 ], [ %__c2.0, %bb6 ]		; <i32> [#uses=2]
+	%iftmp.1.0 = phi i1 [ false, %bb5 ], [ true, %bb6 ]		; <i1> [#uses=1]
+	br i1 %iftmp.1.0, label %bb, label %bb9
+
+bb9:		; preds = %bb7
+	%2 = add i32 %s.0, 2		; <i32> [#uses=1]
+	br label %bb
+}