Allow target to place 2-address pass inserted copies in better spots. Thumb2 will use this to try to avoid breaking up IT blocks.

llvm-svn: 105745

1 files changed, 43 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/Thumb2InstrInfo.cpp b/llvm/lib/Target/ARM/Thumb2InstrInfo.cpp
index 280fd3ed52b..8c19b9f5a62 100644
--- a/llvm/lib/Target/ARM/Thumb2InstrInfo.cpp
+++ b/llvm/lib/Target/ARM/Thumb2InstrInfo.cpp
@@ -503,3 +503,46 @@ bool llvm::rewriteT2FrameIndex(MachineInstr &MI, unsigned FrameRegIdx,
   Offset = (isSub) ? -Offset : Offset;
   return Offset == 0;
 }
+
+/// scheduleTwoAddrSource - Schedule the copy / re-mat of the source of the
+/// two-addrss instruction inserted by two-address pass.
+void
+Thumb2InstrInfo::scheduleTwoAddrSource(MachineInstr *SrcMI,
+                                       MachineInstr *UseMI,
+                                       const TargetRegisterInfo &TRI) const {
+  if (SrcMI->getOpcode() != ARM::tMOVgpr2gpr ||
+      SrcMI->getOperand(1).isKill())
+    return;
+
+  unsigned PredReg = 0;
+  ARMCC::CondCodes CC = llvm::getInstrPredicate(UseMI, PredReg);
+  if (CC == ARMCC::AL || PredReg != ARM::CPSR)
+    return;
+
+  // Schedule the copy so it doesn't come between previous instructions
+  // and UseMI which can form an IT block.
+  unsigned SrcReg = SrcMI->getOperand(1).getReg();
+  ARMCC::CondCodes OCC = ARMCC::getOppositeCondition(CC);
+  MachineBasicBlock *MBB = UseMI->getParent();
+  MachineBasicBlock::iterator MBBI = SrcMI;
+  unsigned NumInsts = 0;
+  while (--MBBI != MBB->begin()) {
+    if (MBBI->isDebugValue())
+      continue;
+
+    MachineInstr *NMI = &*MBBI;
+    ARMCC::CondCodes NCC = llvm::getInstrPredicate(NMI, PredReg);
+    if (!(NCC == CC || NCC == OCC) ||
+        NMI->modifiesRegister(SrcReg, &TRI) ||
+        NMI->definesRegister(ARM::CPSR))
+      break;
+    if (++NumInsts == 4)
+      // Too many in a row!
+      return;
+  }
+
+  if (NumInsts) {
+    MBB->remove(SrcMI);
+    MBB->insert(++MBBI, SrcMI);
+  }
+}