From: Hal Finkel <hfinkel@anl.gov>
Date: Wed, 28 May 2014 15:33:19 +0000 (+0000)
Subject: Revert "[DAGCombiner] Split up an indexed load if only the base pointer value is... 
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=9b7716192728fbdd8ae2ba9a13dcd65d7fe6509f;p=oota-llvm.git

Revert "[DAGCombiner] Split up an indexed load if only the base pointer value is live"

This reverts r208640 (I've just XFAILed the test) because it broke ppc64/Linux
self-hosting. Because nearly every regression test triggers a segfault, I hope
this will be easy to fix.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209747 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 2d2fd53447e..c4089446f08 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -167,7 +167,6 @@ namespace {
 
     bool CombineToPreIndexedLoadStore(SDNode *N);
     bool CombineToPostIndexedLoadStore(SDNode *N);
-    SDValue SplitIndexingFromLoad(LoadSDNode *LD);
     bool SliceUpLoad(SDNode *N);
 
     void ReplaceLoadWithPromotedLoad(SDNode *Load, SDNode *ExtLoad);
@@ -762,14 +761,10 @@ CommitTargetLoweringOpt(const TargetLowering::TargetLoweringOpt &TLO) {
 
     // If the operands of this node are only used by the node, they will now
     // be dead.  Make sure to visit them first to delete dead nodes early.
-    for (unsigned i = 0, e = TLO.Old.getNode()->getNumOperands(); i != e; ++i) {
-      SDNode *Op = TLO.Old.getNode()->getOperand(i).getNode();
-      // For an operand generating multiple values, one of the values may
-      // become dead allowing further simplification (e.g. split index
-      // arithmetic from an indexed load).
-      if (Op->hasOneUse() || Op->getNumValues() > 1)
-        AddToWorkList(Op);
-    }
+    for (unsigned i = 0, e = TLO.Old.getNode()->getNumOperands(); i != e; ++i)
+      if (TLO.Old.getNode()->getOperand(i).getNode()->hasOneUse())
+        AddToWorkList(TLO.Old.getNode()->getOperand(i).getNode());
+
     DAG.DeleteNode(TLO.Old.getNode());
   }
 }
@@ -7849,17 +7844,6 @@ bool DAGCombiner::CombineToPostIndexedLoadStore(SDNode *N) {
   return false;
 }
 
-/// \brief Return the base-pointer arithmetic from an indexed \p LD.
-SDValue DAGCombiner::SplitIndexingFromLoad(LoadSDNode *LD) {
-  ISD::MemIndexedMode AM = LD->getAddressingMode();
-  assert(AM != ISD::UNINDEXED);
-  SDValue BP = LD->getOperand(1);
-  SDValue Inc = LD->getOperand(2);
-  unsigned Opc =
-      (AM == ISD::PRE_INC || AM == ISD::POST_INC ? ISD::ADD : ISD::SUB);
-  return DAG.getNode(Opc, SDLoc(LD), BP.getSimpleValueType(), BP, Inc);
-}
-
 SDValue DAGCombiner::visitLOAD(SDNode *N) {
   LoadSDNode *LD  = cast<LoadSDNode>(N);
   SDValue Chain = LD->getChain();
@@ -7896,16 +7880,8 @@ SDValue DAGCombiner::visitLOAD(SDNode *N) {
     } else {
       // Indexed loads.
       assert(N->getValueType(2) == MVT::Other && "Malformed indexed loads?");
-      if (!N->hasAnyUseOfValue(0)) {
+      if (!N->hasAnyUseOfValue(0) && !N->hasAnyUseOfValue(1)) {
         SDValue Undef = DAG.getUNDEF(N->getValueType(0));
-        SDValue Index;
-        if (N->hasAnyUseOfValue(1)) {
-          Index = SplitIndexingFromLoad(LD);
-          // Try to fold the base pointer arithmetic into subsequent loads and
-          // stores.
-          AddUsersToWorkList(N);
-        } else
-          Index = DAG.getUNDEF(N->getValueType(1));
         DEBUG(dbgs() << "\nReplacing.7 ";
               N->dump(&DAG);
               dbgs() << "\nWith: ";
@@ -7913,7 +7889,8 @@ SDValue DAGCombiner::visitLOAD(SDNode *N) {
               dbgs() << " and 2 other values\n");
         WorkListRemover DeadNodes(*this);
         DAG.ReplaceAllUsesOfValueWith(SDValue(N, 0), Undef);
-        DAG.ReplaceAllUsesOfValueWith(SDValue(N, 1), Index);
+        DAG.ReplaceAllUsesOfValueWith(SDValue(N, 1),
+                                      DAG.getUNDEF(N->getValueType(1)));
         DAG.ReplaceAllUsesOfValueWith(SDValue(N, 2), Chain);
         removeFromWorkList(N);
         DAG.DeleteNode(N);
diff --git a/test/CodeGen/AArch64/arm64-dagcombiner-dead-indexed-load.ll b/test/CodeGen/AArch64/arm64-dagcombiner-dead-indexed-load.ll
index 2cf01357324..6eed48bf62e 100644
--- a/test/CodeGen/AArch64/arm64-dagcombiner-dead-indexed-load.ll
+++ b/test/CodeGen/AArch64/arm64-dagcombiner-dead-indexed-load.ll
@@ -1,5 +1,8 @@
 ; RUN: llc -mcpu=cyclone < %s | FileCheck %s
 
+; r208640 broke ppc64/Linux self-hosting; xfailing while this is worked on.
+; XFAIL: *
+
 target datalayout = "e-i64:64-n32:64-S128"
 target triple = "arm64-apple-ios"