From b0f5973bee566269f41d1cc21b7a1d3bede1d837 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Mon, 21 Sep 2009 04:32:32 +0000
Subject: [PATCH] Fix PR4986. "r1024 = insert_subreg r1024, undef, 2" cannot be
 turned in an implicit_def. Instead, it's an identity copy so it should be
 eliminated. Also make sure to update livevariable kill information.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82436 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/LiveIntervalAnalysis.cpp            | 33 ++++++++++++++++--------
 test/CodeGen/ARM/2009-09-20-LiveIntervalsBug.ll | 34 +++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 10 deletions(-)
 create mode 100644 test/CodeGen/ARM/2009-09-20-LiveIntervalsBug.ll

diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index c690ac32412..abab1eef686 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -109,18 +109,15 @@ void LiveIntervals::releaseMemory() {
 }
 
 static bool CanTurnIntoImplicitDef(MachineInstr *MI, unsigned Reg,
-                                   const TargetInstrInfo *tii_) {
+                                   unsigned OpIdx, const TargetInstrInfo *tii_){
   unsigned SrcReg, DstReg, SrcSubReg, DstSubReg;
   if (tii_->isMoveInstr(*MI, SrcReg, DstReg, SrcSubReg, DstSubReg) &&
       Reg == SrcReg)
     return true;
 
-  if ((MI->getOpcode() == TargetInstrInfo::INSERT_SUBREG ||
-       MI->getOpcode() == TargetInstrInfo::SUBREG_TO_REG) &&
-      MI->getOperand(2).getReg() == Reg)
+  if (OpIdx == 2 && MI->getOpcode() == TargetInstrInfo::SUBREG_TO_REG)
     return true;
-  if (MI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG &&
-      MI->getOperand(1).getReg() == Reg)
+  if (OpIdx == 1 && MI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG)
     return true;
   return false;
 }
@@ -148,6 +145,20 @@ void LiveIntervals::processImplicitDefs() {
         continue;
       }
 
+      if (MI->getOpcode() == TargetInstrInfo::INSERT_SUBREG) {
+        MachineOperand &MO = MI->getOperand(2);
+        if (ImpDefRegs.count(MO.getReg())) {
+          // %reg1032<def> = INSERT_SUBREG %reg1032, undef, 2
+          // This is an identity copy, eliminate it now.
+          if (MO.isKill()) {
+            LiveVariables::VarInfo& vi = lv_->getVarInfo(MO.getReg());
+            vi.removeKill(MI);
+          }
+          MI->eraseFromParent();
+          continue;
+        }
+      }
+
       bool ChangedToImpDef = false;
       for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
         MachineOperand& MO = MI->getOperand(i);
@@ -159,13 +170,16 @@ void LiveIntervals::processImplicitDefs() {
         if (!ImpDefRegs.count(Reg))
           continue;
         // Use is a copy, just turn it into an implicit_def.
-        if (CanTurnIntoImplicitDef(MI, Reg, tii_)) {
+        if (CanTurnIntoImplicitDef(MI, Reg, i, tii_)) {
           bool isKill = MO.isKill();
           MI->setDesc(tii_->get(TargetInstrInfo::IMPLICIT_DEF));
           for (int j = MI->getNumOperands() - 1, ee = 0; j > ee; --j)
             MI->RemoveOperand(j);
-          if (isKill)
+          if (isKill) {
             ImpDefRegs.erase(Reg);
+            LiveVariables::VarInfo& vi = lv_->getVarInfo(Reg);
+            vi.removeKill(MI);
+          }
           ChangedToImpDef = true;
           break;
         }
@@ -738,8 +752,7 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
       MachineInstr *Kill = vi.Kills[i];
       MachineInstrIndex killIdx =
         getNextSlot(getUseIndex(getInstructionIndex(Kill)));
-      LiveRange LR(getMBBStartIdx(Kill->getParent()),
-                   killIdx, ValNo);
+      LiveRange LR(getMBBStartIdx(Kill->getParent()), killIdx, ValNo);
       interval.addRange(LR);
       ValNo->addKill(killIdx);
       DEBUG(errs() << " +" << LR);
diff --git a/test/CodeGen/ARM/2009-09-20-LiveIntervalsBug.ll b/test/CodeGen/ARM/2009-09-20-LiveIntervalsBug.ll
new file mode 100644
index 00000000000..980f8ce6fa1
--- /dev/null
+++ b/test/CodeGen/ARM/2009-09-20-LiveIntervalsBug.ll
@@ -0,0 +1,34 @@
+; RUN: llc < %s -mtriple=arm-eabi -mattr=+neon -mcpu=cortex-a9
+
+; PR4986
+
+define arm_aapcs_vfpcc void @foo(i8* nocapture %pBuffer, i32 %numItems) nounwind {
+entry:
+  br i1 undef, label %return, label %bb.preheader
+
+bb.preheader:                                     ; preds = %entry
+  br label %bb
+
+bb:                                               ; preds = %bb, %bb.preheader
+  %0 = shufflevector <4 x float> zeroinitializer, <4 x float> undef, <4 x i32> zeroinitializer ; <<4 x float>> [#uses=1]
+  %1 = insertelement <4 x float> %0, float undef, i32 1 ; <<4 x float>> [#uses=1]
+  %2 = insertelement <4 x float> %1, float undef, i32 2 ; <<4 x float>> [#uses=1]
+  %3 = insertelement <4 x float> %2, float undef, i32 3 ; <<4 x float>> [#uses=1]
+  %4 = fmul <4 x float> undef, %3                 ; <<4 x float>> [#uses=1]
+  %5 = extractelement <4 x float> %4, i32 3       ; <float> [#uses=1]
+  store float %5, float* undef, align 4
+  br i1 undef, label %return, label %bb
+
+return:                                           ; preds = %bb, %entry
+  ret void
+}
+
+define arm_aapcs_vfpcc <4 x float> @bar(i8* nocapture %pBuffer, i32 %numItems) nounwind {
+  %1 = shufflevector <4 x float> zeroinitializer, <4 x float> undef, <4 x i32> zeroinitializer ; <<4 x float>> [#uses=1]
+  %2 = insertelement <4 x float> %1, float undef, i32 1 ; <<4 x float>> [#uses=1]
+  %3 = insertelement <4 x float> %2, float undef, i32 2 ; <<4 x float>> [#uses=1]
+  %4 = insertelement <4 x float> %3, float undef, i32 3 ; <<4 x float>> [#uses=1]
+  %5 = shufflevector <4 x float> %4, <4 x float> undef, <2 x i32> <i32 0, i32 1> ; <<2 x float>> [#uses=1]
+  %6 = shufflevector <2 x float> %5, <2 x float> undef, <4 x i32> <i32 1, i32 1, i32 1, i32 1> ; <<4 x float>> [#uses=1]
+  ret <4 x float> %6
+}
-- 
2.11.0