LSR: teach isSimplifiedLoopNest to handle PHI IVUsers.

llvm-svn: 153132

2 files changed, 40 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/IVUsers.cpp b/llvm/lib/Analysis/IVUsers.cpp
index 308729fcf12..463584db897 100644
--- a/llvm/lib/Analysis/IVUsers.cpp
+++ b/llvm/lib/Analysis/IVUsers.cpp
@@ -148,7 +148,14 @@ bool IVUsers::AddUsersIfInteresting(Instruction *I,
 
     // Only consider IVUsers that are dominated by simplified loop
     // headers. Otherwise, SCEVExpander will crash.
-    if (!isSimplifiedLoopNest(User->getParent(), DT, LI, SimpleLoopNests))
+    BasicBlock *UseBB = User->getParent();
+    // A phi's use is live out of its predecessor block.
+    if (PHINode *PHI = dyn_cast<PHINode>(User)) {
+      unsigned OperandNo = UI.getOperandNo();
+      unsigned ValNo = PHINode::getIncomingValueNumForOperand(OperandNo);
+      UseBB = PHI->getIncomingBlock(ValNo);
+    }
+    if (!isSimplifiedLoopNest(UseBB, DT, LI, SimpleLoopNests))
       return false;
 
     // Descend recursively, but not into PHI nodes outside the current loop.
diff --git a/llvm/test/Transforms/LoopStrengthReduce/2012-03-15-nopreheader.ll b/llvm/test/Transforms/LoopStrengthReduce/2012-03-15-nopreheader.ll
index 01f9276dc28..0172492edc9 100644
--- a/llvm/test/Transforms/LoopStrengthReduce/2012-03-15-nopreheader.ll
+++ b/llvm/test/Transforms/LoopStrengthReduce/2012-03-15-nopreheader.ll
@@ -49,6 +49,8 @@ return:                                           ; preds = %if.end677, %doshell
   ret void
 }
 
+; Another case with a dominating loop that does not contain the IV
+; User. Just make sure it doesn't assert.
 define void @nopreheader2() nounwind ssp {
 entry:
   indirectbr i8* undef, [label %while.cond, label %return]
@@ -121,3 +123,33 @@ while.body94:                                     ; preds = %lor.rhs87, %while.c
 return:                                           ; preds = %if.end216, %land.lhs.true183, %land.lhs.true, %while.end52, %lor.lhs.false, %while.end, %entry
   ret void
 }
+
+; Test a phi operand IV User dominated by a no-preheader loop.
+define void @nopreheader3() nounwind uwtable ssp align 2 {
+entry:
+  indirectbr i8* blockaddress(@nopreheader3, %if.end10), [label %if.end22, label %if.end10]
+
+if.end10:                                         ; preds = %entry
+  indirectbr i8* blockaddress(@nopreheader3, %if.end6.i), [label %if.end22, label %if.end6.i]
+
+if.end6.i:                                        ; preds = %if.end10
+  indirectbr i8* blockaddress(@nopreheader3, %while.cond2.preheader.i.i), [label %if.then12, label %while.cond2.preheader.i.i]
+
+while.cond2.preheader.i.i:                        ; preds = %while.end.i18.i, %if.end6.i
+  indirectbr i8* blockaddress(@nopreheader3, %while.cond2.i.i), [label %while.cond2.i.i]
+
+while.cond2.i.i:                                  ; preds = %while.cond2.i.i, %while.cond2.preheader.i.i
+  %i1.1.i14.i = phi i32 [ %add.i15.i, %while.cond2.i.i ], [ undef, %while.cond2.preheader.i.i ]
+  %add.i15.i = add nsw i32 %i1.1.i14.i, undef
+  indirectbr i8* blockaddress(@nopreheader3, %while.end.i18.i), [label %while.cond2.i.i, label %while.end.i18.i]
+
+while.end.i18.i:                                  ; preds = %while.cond2.i.i
+  indirectbr i8* blockaddress(@nopreheader3, %while.cond2.preheader.i.i), [label %if.then12, label %while.cond2.preheader.i.i]
+
+if.then12:                                        ; preds = %while.end.i18.i, %if.end6.i
+  %i1.0.lcssa.i.i = phi i32 [ undef, %if.end6.i ], [ %i1.1.i14.i, %while.end.i18.i ]
+  indirectbr i8* blockaddress(@nopreheader3, %if.end22), [label %if.end22]
+
+if.end22:                                         ; preds = %if.then12, %if.end10, %entry
+  ret void
+}