From 3c0ed08996d8347fd18a8fe78caf1aac74c44379 Mon Sep 17 00:00:00 2001
From: Andrew Trick <atrick@apple.com>
Date: Tue, 7 Jan 2014 01:50:58 +0000
Subject: [PATCH] Revert "indvars: sink truncates outside the loop."

This reverts commit r198654.

One of the bots reported a SciMark failure.

llvm-svn: 198659
---
 llvm/lib/Transforms/Scalar/IndVarSimplify.cpp   | 27 ++++---------------------
 llvm/test/Transforms/IndVarSimplify/iv-widen.ll |  7 +++----
 2 files changed, 7 insertions(+), 27 deletions(-)

diff --git a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
index 08df953..1076e50 100644
--- a/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -883,8 +883,6 @@ const SCEVAddRecExpr *WidenIV::GetWideRecurrence(Instruction *NarrowUse) {
 /// This IV user cannot be widen. Replace this use of the original narrow IV
 /// with a truncation of the new wide IV to isolate and eliminate the narrow IV.
 static void truncateIVUse(NarrowIVDefUse DU, DominatorTree *DT) {
-  DEBUG(dbgs() << "INDVARS: Truncate IV " << *DU.WideDef
-        << " for user " << *DU.NarrowUse << "\n");
   IRBuilder<> Builder(getInsertPointForUses(DU.NarrowUse, DU.NarrowDef, DT));
   Value *Trunc = Builder.CreateTrunc(DU.WideDef, DU.NarrowDef->getType());
   DU.NarrowUse->replaceUsesOfWith(DU.NarrowDef, Trunc);
@@ -895,27 +893,10 @@ static void truncateIVUse(NarrowIVDefUse DU, DominatorTree *DT) {
 Instruction *WidenIV::WidenIVUse(NarrowIVDefUse DU, SCEVExpander &Rewriter) {
 
   // Stop traversing the def-use chain at inner-loop phis or post-loop phis.
-  if (PHINode *UsePhi = dyn_cast<PHINode>(DU.NarrowUse)) {
-    if (LI->getLoopFor(UsePhi->getParent()) != L) {
-      // For LCSSA phis, sink the truncate outside the loop.
-      // After SimplifyCFG most loop exit targets have a single predecessor.
-      // Otherwise fall back to a truncate within the loop.
-      if (UsePhi->getNumOperands() != 1)
-        truncateIVUse(DU, DT);
-      else {
-        PHINode *WidePhi =
-          PHINode::Create(DU.WideDef->getType(), 1, UsePhi->getName() + ".wide",
-                          UsePhi);
-        WidePhi->addIncoming(DU.WideDef, UsePhi->getIncomingBlock(0));
-        IRBuilder<> Builder(WidePhi->getParent()->getFirstInsertionPt());
-        Value *Trunc = Builder.CreateTrunc(WidePhi, DU.NarrowDef->getType());
-        UsePhi->replaceAllUsesWith(Trunc);
-        DeadInsts.push_back(UsePhi);
-        DEBUG(dbgs() << "INDVARS: Widen lcssa phi " << *UsePhi
-              << " to " << *WidePhi << "\n");
-      }
-      return 0;
-    }
+  if (isa<PHINode>(DU.NarrowUse) &&
+      LI->getLoopFor(DU.NarrowUse->getParent()) != L) {
+    truncateIVUse(DU, DT);
+    return 0;
   }
   // Our raison d'etre! Eliminate sign and zero extension.
   if (IsSigned ? isa<SExtInst>(DU.NarrowUse) : isa<ZExtInst>(DU.NarrowUse)) {
diff --git a/llvm/test/Transforms/IndVarSimplify/iv-widen.ll b/llvm/test/Transforms/IndVarSimplify/iv-widen.ll
index c899e2f..12067ab 100644
--- a/llvm/test/Transforms/IndVarSimplify/iv-widen.ll
+++ b/llvm/test/Transforms/IndVarSimplify/iv-widen.ll
@@ -7,11 +7,10 @@ target triple = "x86_64-apple-darwin"
 ; Only one phi now.
 ; CHECK: phi
 ; CHECK-NOT: phi
-; One trunc for the gep.
+; We now get 2 trunc, one for the gep and one for the lcssa phi.
 ; CHECK: trunc i64 %indvars.iv to i32
-; One trunc for the dummy() call.
-; CHECK-LABEL: exit24:
-; CHECK: trunc i64 {{.*}}lcssa.wide to i32
+; CHECK: trunc i64 %indvars.iv to i32
+; CHECK-LABEL: B24:
 define void @sloop(i32* %a) {
 Prologue:
   br i1 undef, label %B18, label %B6
-- 
2.7.4