reverting thumb1 scavenging default due to test failure while I figure out what's up.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83501 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/TargetRegisterInfo.h

@@ -561,12 +561,6 @@ public:
     return false;
   }
 
-  /// requiresFrameIndexScavenging - returns true if the target requires post
-  /// PEI scavenging of registers for materializing frame index constants.
-  virtual bool requiresFrameIndexScavenging(const MachineFunction &MF) const {
-    return false;
-  }
-
   /// hasFP - Return true if the specified function should have a dedicated
   /// frame pointer register. For most targets this is true only if the function
   /// has variable sized allocas or if frame pointer elimination is disabled.

lib/CodeGen/PrologEpilogInserter.cpp

@@ -44,6 +44,16 @@ char PEI::ID = 0;
 static RegisterPass<PEI>
 X("prologepilog", "Prologue/Epilogue Insertion");
 
+// FIXME: For now, the frame index scavenging is off by default and only
+// used by the Thumb1 target. When it's the default and replaces the current
+// on-the-fly PEI scavenging for all targets, requiresRegisterScavenging()
+// will replace this.
+cl::opt<bool>
+FrameIndexVirtualScavenging("enable-frame-index-scavenging",
+                            cl::Hidden,
+                            cl::desc("Enable frame index elimination with"
+                                     "virtual register scavenging"));
+
 /// createPrologEpilogCodeInserter - This function returns a pass that inserts
 /// prolog and epilog code, and eliminates abstract frame references.
 ///
@@ -56,7 +66,6 @@ bool PEI::runOnMachineFunction(MachineFunction &Fn) {
   const Function* F = Fn.getFunction();
   const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
   RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL;
-  FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(Fn);
 
   // Get MachineModuleInfo so that we can track the construction of the
   // frame.

lib/CodeGen/PrologEpilogInserter.h

@@ -95,11 +95,6 @@ namespace llvm {
     // functions.
     bool ShrinkWrapThisFunction;
 
-    // Flag to control whether to use the register scavenger to resolve
-    // frame index materialization registers. Set according to
-    // TRI->requiresFrameIndexScavenging() for the curren function.
-    bool FrameIndexVirtualScavenging;
-
     // When using the scavenger post-pass to resolve frame reference
     // materialization registers, maintain a map of the registers to
     // the constant value and SP adjustment associated with it.

lib/Target/ARM/Thumb1RegisterInfo.cpp

@@ -37,6 +37,11 @@
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 
+// FIXME: This cmd line option conditionalizes the new register scavenging
+// implemenation in PEI. Remove the option when scavenging works well enough
+// to be the default.
+extern cl::opt<bool> FrameIndexVirtualScavenging;
+
 Thumb1RegisterInfo::Thumb1RegisterInfo(const ARMBaseInstrInfo &tii,
                                        const ARMSubtarget &sti)
   : ARMBaseRegisterInfo(tii, sti) {
@@ -79,13 +84,7 @@ Thumb1RegisterInfo::getPhysicalRegisterRegClass(unsigned Reg, EVT VT) const {
 
 bool
 Thumb1RegisterInfo::requiresRegisterScavenging(const MachineFunction &MF) const {
-  return true;
-}
-
-bool
-Thumb1RegisterInfo::requiresFrameIndexScavenging(const MachineFunction &MF)
-  const {
-  return true;
+  return FrameIndexVirtualScavenging;
 }
 
 bool Thumb1RegisterInfo::hasReservedCallFrame(MachineFunction &MF) const {
@@ -129,7 +128,13 @@ void emitThumbRegPlusImmInReg(MachineBasicBlock &MBB,
     unsigned LdReg = DestReg;
     if (DestReg == ARM::SP) {
       assert(BaseReg == ARM::SP && "Unexpected!");
-      LdReg = MF.getRegInfo().createVirtualRegister(ARM::tGPRRegisterClass);
+      if (FrameIndexVirtualScavenging) {
+        LdReg = MF.getRegInfo().createVirtualRegister(ARM::tGPRRegisterClass);
+      } else {
+        LdReg = ARM::R3;
+        BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVtgpr2gpr), ARM::R12)
+          .addReg(ARM::R3, RegState::Kill);
+      }
     }
 
     if (NumBytes <= 255 && NumBytes >= 0)
@@ -154,6 +159,10 @@ void emitThumbRegPlusImmInReg(MachineBasicBlock &MBB,
     else
       MIB.addReg(LdReg).addReg(BaseReg, RegState::Kill);
     AddDefaultPred(MIB);
+
+    if (!FrameIndexVirtualScavenging && DestReg == ARM::SP)
+      BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVgpr2tgpr), ARM::R3)
+        .addReg(ARM::R12, RegState::Kill);
 }
 
 /// calcNumMI - Returns the number of instructions required to materialize
@@ -626,6 +635,7 @@ Thumb1RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
     else  // tLDR has an extra register operand.
       MI.addOperand(MachineOperand::CreateReg(0, false));
   } else if (Desc.mayStore()) {
+    if (FrameIndexVirtualScavenging) {
       VReg = MF.getRegInfo().createVirtualRegister(ARM::tGPRRegisterClass);
       assert (Value && "Frame index virtual allocated, but Value arg is NULL!");
       *Value = Offset;
@@ -648,6 +658,52 @@ Thumb1RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
         MI.addOperand(MachineOperand::CreateReg(FrameReg, false));
       else // tSTR has an extra register operand.
         MI.addOperand(MachineOperand::CreateReg(0, false));
+    } else {
+      // FIXME! This is horrific!!! We need register scavenging.
+      // Our temporary workaround has marked r3 unavailable. Of course, r3 is
+      // also a ABI register so it's possible that is is the register that is
+      // being storing here. If that's the case, we do the following:
+      // r12 = r2
+      // Use r2 to materialize sp + offset
+      // str r3, r2
+      // r2 = r12
+      unsigned ValReg = MI.getOperand(0).getReg();
+      unsigned TmpReg = ARM::R3;
+      bool UseRR = false;
+      if (ValReg == ARM::R3) {
+        BuildMI(MBB, II, dl, TII.get(ARM::tMOVtgpr2gpr), ARM::R12)
+          .addReg(ARM::R2, RegState::Kill);
+        TmpReg = ARM::R2;
+      }
+      if (TmpReg == ARM::R3 && AFI->isR3LiveIn())
+        BuildMI(MBB, II, dl, TII.get(ARM::tMOVtgpr2gpr), ARM::R12)
+          .addReg(ARM::R3, RegState::Kill);
+      if (Opcode == ARM::tSpill) {
+        if (FrameReg == ARM::SP)
+          emitThumbRegPlusImmInReg(MBB, II, TmpReg, FrameReg,
+                                   Offset, false, TII, *this, dl);
+        else {
+          emitLoadConstPool(MBB, II, dl, TmpReg, 0, Offset);
+          UseRR = true;
+        }
+      } else
+        emitThumbRegPlusImmediate(MBB, II, TmpReg, FrameReg, Offset, TII,
+                                  *this, dl);
+      MI.setDesc(TII.get(ARM::tSTR));
+      MI.getOperand(i).ChangeToRegister(TmpReg, false, false, true);
+      if (UseRR)  // Use [reg, reg] addrmode.
+        MI.addOperand(MachineOperand::CreateReg(FrameReg, false));
+      else // tSTR has an extra register operand.
+        MI.addOperand(MachineOperand::CreateReg(0, false));
+
+      MachineBasicBlock::iterator NII = next(II);
+      if (ValReg == ARM::R3)
+        BuildMI(MBB, NII, dl, TII.get(ARM::tMOVgpr2tgpr), ARM::R2)
+          .addReg(ARM::R12, RegState::Kill);
+      if (TmpReg == ARM::R3 && AFI->isR3LiveIn())
+        BuildMI(MBB, NII, dl, TII.get(ARM::tMOVgpr2tgpr), ARM::R3)
+          .addReg(ARM::R12, RegState::Kill);
+    }
   } else
     assert(false && "Unexpected opcode!");
 

lib/Target/ARM/Thumb1RegisterInfo.h

@@ -41,7 +41,6 @@ public:
     getPhysicalRegisterRegClass(unsigned Reg, EVT VT = MVT::Other) const;
 
   bool requiresRegisterScavenging(const MachineFunction &MF) const;
-  bool requiresFrameIndexScavenging(const MachineFunction &MF) const;
 
   bool hasReservedCallFrame(MachineFunction &MF) const;