From 20599ea4bced03634a54b52e98d261018366f279 Mon Sep 17 00:00:00 2001
From: Tim Northover <Tim.Northover@arm.com>
Date: Wed, 29 Aug 2012 16:36:07 +0000
Subject: [PATCH] Refactor setExecutionDomain to be clearer about what it's
 doing and more robust.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@162844 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM/ARMBaseInstrInfo.cpp | 98 ++++++++++++++++-------------
 1 file changed, 53 insertions(+), 45 deletions(-)

diff --git a/lib/Target/ARM/ARMBaseInstrInfo.cpp b/lib/Target/ARM/ARMBaseInstrInfo.cpp
index 4f203eac566..41d0c570bf4 100644
--- a/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -3397,13 +3397,28 @@ ARMBaseInstrInfo::getExecutionDomain(const MachineInstr *MI) const {
   return std::make_pair(ExeGeneric, 0);
 }
 
+static unsigned getCorrespondingDRegAndLane(const TargetRegisterInfo *TRI,
+                                            unsigned SReg, unsigned &Lane) {
+  unsigned DReg = TRI->getMatchingSuperReg(SReg, ARM::ssub_0, &ARM::DPRRegClass);
+  Lane = 0;
+
+  if (DReg != ARM::NoRegister)
+   return DReg;
+
+  Lane = 1;
+  DReg = TRI->getMatchingSuperReg(SReg, ARM::ssub_1, &ARM::DPRRegClass);
+
+  assert(DReg && "S-register with no D super-register?");
+  return DReg;
+}
+
+
 void
 ARMBaseInstrInfo::setExecutionDomain(MachineInstr *MI, unsigned Domain) const {
   unsigned DstReg, SrcReg, DReg;
   unsigned Lane;
   MachineInstrBuilder MIB(MI);
   const TargetRegisterInfo *TRI = &getRegisterInfo();
-  bool isKill;
   switch (MI->getOpcode()) {
     default:
       llvm_unreachable("cannot handle opcode!");
@@ -3414,77 +3429,70 @@ ARMBaseInstrInfo::setExecutionDomain(MachineInstr *MI, unsigned Domain) const {
 
       // Zap the predicate operands.
       assert(!isPredicated(MI) && "Cannot predicate a VORRd");
-      MI->RemoveOperand(3);
-      MI->RemoveOperand(2);
 
-      // Change to a VORRd which requires two identical use operands.
-      MI->setDesc(get(ARM::VORRd));
+      // Source instruction is %DDst = VMOVD %DSrc, 14, %noreg (; implicits)
+      DstReg = MI->getOperand(0).getReg();
+      SrcReg = MI->getOperand(1).getReg();
 
-      // Add the extra source operand and new predicates.
-      // This will go before any implicit ops.
-      AddDefaultPred(MachineInstrBuilder(MI).addOperand(MI->getOperand(1)));
+      for (unsigned i = MI->getDesc().getNumOperands(); i; --i)
+        MI->RemoveOperand(i-1);
+
+      // Change to a %DDst = VORRd %DSrc, %DSrc, 14, %noreg (; implicits)
+      MI->setDesc(get(ARM::VORRd));
+      AddDefaultPred(MIB.addReg(DstReg, RegState::Define)
+                        .addReg(SrcReg)
+                        .addReg(SrcReg));
       break;
     case ARM::VMOVRS:
       if (Domain != ExeNEON)
         break;
       assert(!isPredicated(MI) && "Cannot predicate a VGETLN");
 
+      // Source instruction is %RDst = VMOVRS %SSrc, 14, %noreg (; implicits)
       DstReg = MI->getOperand(0).getReg();
       SrcReg = MI->getOperand(1).getReg();
 
-      DReg = TRI->getMatchingSuperReg(SrcReg, ARM::ssub_0, &ARM::DPRRegClass);
-      Lane = 0;
-      if (DReg == ARM::NoRegister) {
-        DReg = TRI->getMatchingSuperReg(SrcReg, ARM::ssub_1, &ARM::DPRRegClass);
-        Lane = 1;
-        assert(DReg && "S-register with no D super-register?");
-      }
+      for (unsigned i = MI->getDesc().getNumOperands(); i; --i)
+        MI->RemoveOperand(i-1);
 
-      MI->RemoveOperand(3);
-      MI->RemoveOperand(2);
-      MI->RemoveOperand(1);
+      DReg = getCorrespondingDRegAndLane(TRI, SrcReg, Lane);
 
+      // Convert to %RDst = VGETLNi32 %DSrc, Lane, 14, %noreg (; imps)
+      // Note that DSrc has been widened and the other lane may be undef, which
+      // contaminates the entire register.
       MI->setDesc(get(ARM::VGETLNi32));
-      MIB.addReg(DReg);
-      MIB.addImm(Lane);
+      AddDefaultPred(MIB.addReg(DstReg, RegState::Define)
+                        .addReg(DReg, RegState::Undef)
+                        .addImm(Lane));
 
-      MIB->getOperand(1).setIsUndef();
+      // The old source should be an implicit use, otherwise we might think it
+      // was dead before here.
       MIB.addReg(SrcReg, RegState::Implicit);
-
-      AddDefaultPred(MIB);
       break;
     case ARM::VMOVSR:
       if (Domain != ExeNEON)
         break;
       assert(!isPredicated(MI) && "Cannot predicate a VSETLN");
 
+      // Source instruction is %SDst = VMOVSR %RSrc, 14, %noreg (; implicits)
       DstReg = MI->getOperand(0).getReg();
       SrcReg = MI->getOperand(1).getReg();
-      DReg = TRI->getMatchingSuperReg(DstReg, ARM::ssub_0, &ARM::DPRRegClass);
-      Lane = 0;
-      if (DReg == ARM::NoRegister) {
-        DReg = TRI->getMatchingSuperReg(DstReg, ARM::ssub_1, &ARM::DPRRegClass);
-        Lane = 1;
-        assert(DReg && "S-register with no D super-register?");
-      }
-      isKill = MI->getOperand(0).isKill();
-
-      MI->RemoveOperand(3);
-      MI->RemoveOperand(2);
-      MI->RemoveOperand(1);
-      MI->RemoveOperand(0);
 
-      MI->setDesc(get(ARM::VSETLNi32));
-      MIB.addReg(DReg, RegState::Define);
-      MIB.addReg(DReg, RegState::Undef);
-      MIB.addReg(SrcReg);
-      MIB.addImm(Lane);
+      for (unsigned i = MI->getDesc().getNumOperands(); i; --i)
+        MI->RemoveOperand(i-1);
 
-      if (isKill)
-        MIB->addRegisterKilled(DstReg, TRI, true);
-      MIB->addRegisterDefined(DstReg, TRI);
+      DReg = getCorrespondingDRegAndLane(TRI, DstReg, Lane);
 
-      AddDefaultPred(MIB);
+      // Convert to %DDst = VSETLNi32 %DDst, %RSrc, Lane, 14, %noreg (; imps)
+      // Again DDst may be undefined at the beginning of this instruction.
+      MI->setDesc(get(ARM::VSETLNi32));
+      AddDefaultPred(MIB.addReg(DReg, RegState::Define)
+                        .addReg(DReg, RegState::Undef)
+                        .addReg(SrcReg)
+                        .addImm(Lane));
+   
+      // The destination must be marked as set.
+      MIB.addReg(DstReg, RegState::Define | RegState::Implicit);
       break;
   }
 
-- 
2.34.1