[PATCH] D79785: [ARM] Register pressure with -mthumb forces register reload before each call

[Prathamesh via Phabricator via llvm-commits]

prathamesh updated this revision to Diff 269167.
prathamesh added a comment.

Hi John,
Thanks for the review and I am sorry for late response, I was on a leave.
I have the updated the patch with suggested changes, do they look in right direction ?
Testing with make check-llvm shows no unexpected failures.

Thanks,
Prathamesh


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D79785/new/

https://reviews.llvm.org/D79785

Files:
  llvm/lib/Target/ARM/Thumb1InstrInfo.cpp
  llvm/lib/Target/ARM/Thumb1InstrInfo.h


Index: llvm/lib/Target/ARM/Thumb1InstrInfo.h
===================================================================
--- llvm/lib/Target/ARM/Thumb1InstrInfo.h
+++ llvm/lib/Target/ARM/Thumb1InstrInfo.h
@@ -53,6 +53,13 @@
                             const TargetRegisterInfo *TRI) const override;
 
   bool canCopyGluedNodeDuringSchedule(SDNode *N) const override;
+
+protected:
+  virtual MachineInstr *foldMemoryOperandImpl(
+      MachineFunction &MF, MachineInstr &MI, ArrayRef<unsigned> Ops,
+      MachineBasicBlock::iterator InsertPt, MachineInstr &LoadMI,
+      LiveIntervals *LIS = nullptr) const override;
+
 private:
   void expandLoadStackGuard(MachineBasicBlock::iterator MI) const override;
 };
Index: llvm/lib/Target/ARM/Thumb1InstrInfo.cpp
===================================================================
--- llvm/lib/Target/ARM/Thumb1InstrInfo.cpp
+++ llvm/lib/Target/ARM/Thumb1InstrInfo.cpp
@@ -152,3 +152,35 @@
 
   return false;
 }
+
+MachineInstr *Thumb1InstrInfo::foldMemoryOperandImpl(
+      MachineFunction &MF, MachineInstr &MI, ArrayRef<unsigned> Ops,
+      MachineBasicBlock::iterator InsertPt, MachineInstr &LoadMI,
+      LiveIntervals *LIS) const {
+  // Replace:
+  // ldr Rd, func address
+  // blx Rd
+  // with:
+  // bl func
+
+  if (MI.getOpcode() == ARM::tBLXr && LoadMI.getOpcode() == ARM::tLDRpci &&
+      MI.getParent() == LoadMI.getParent()) {
+    unsigned CPI = LoadMI.getOperand(1).getIndex();
+    const MachineConstantPool *MCP = MF.getConstantPool();
+    const MachineConstantPoolEntry &CPE = MCP->getConstants()[CPI];
+    assert(!CPE.isMachineConstantPoolEntry() && "Invalid constpool entry");
+    const Constant *Callee = cast<Constant>(CPE.Val.ConstVal);
+    const char *FuncName = MF.createExternalSymbolName(Callee->getName());
+    MachineInstrBuilder MIB = BuildMI(*MI.getParent(), InsertPt, MI.getDebugLoc(), get(ARM::tBL))
+                                      .add(predOps(ARMCC::AL))
+                                      .addExternalSymbol(FuncName);
+    for (auto &MO: MI.implicit_operands())
+      if (MO.isReg())
+        MIB.addReg(MO.getReg(), RegState::Implicit | RegState::Kill);
+      else if (MO.isRegMask())
+        MIB.add(MO);
+    return MIB.getInstr();
+  }
+
+  return nullptr;
+}


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