[llvm-commits] [llvm] r110423 - in /llvm/trunk: include/llvm/CodeGen/Passes.h include/llvm/Target/TargetInstrInfo.h lib/CodeGen/LLVMTargetMachine.cpp lib/CodeGen/OptimizeCmps.cpp lib/Target/ARM/ARMBaseInstrInfo.cpp lib/Target/ARM/ARMBaseInstrInfo.h
Bill Wendling
isanbard at gmail.com
Thu Aug 5 18:32:49 PDT 2010
Author: void
Date: Thu Aug 5 20:32:48 2010
New Revision: 110423
URL: http://llvm.org/viewvc/llvm-project?rev=110423&view=rev
Log:
Add the Optimize Compares pass (disabled by default).
This pass tries to remove comparison instructions when possible. For instance,
if you have this code:
sub r1, 1
cmp r1, 0
bz L1
and "sub" either sets the same flag as the "cmp" instruction or could be
converted to set the same flag, then we can eliminate the "cmp" instruction all
together. This is a important for ARM where the ALU instructions could set the
CPSR flag, but need a special suffix ('s') to do so.
Added:
llvm/trunk/lib/CodeGen/OptimizeCmps.cpp
Modified:
llvm/trunk/include/llvm/CodeGen/Passes.h
llvm/trunk/include/llvm/Target/TargetInstrInfo.h
llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp
llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.cpp
llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.h
Modified: llvm/trunk/include/llvm/CodeGen/Passes.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/Passes.h?rev=110423&r1=110422&r2=110423&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/Passes.h (original)
+++ llvm/trunk/include/llvm/CodeGen/Passes.h Thu Aug 5 20:32:48 2010
@@ -180,6 +180,10 @@
/// to take advantage of opportunities created during DAG legalization.
FunctionPass *createOptimizePHIsPass();
+ /// createOptimizeCmpsPass - This pass performs redundant comparison removal
+ /// optimization.
+ FunctionPass *createOptimizeCmpsPass();
+
/// createStackSlotColoringPass - This pass performs stack slot coloring.
FunctionPass *createStackSlotColoringPass(bool);
Modified: llvm/trunk/include/llvm/Target/TargetInstrInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Target/TargetInstrInfo.h?rev=110423&r1=110422&r2=110423&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Target/TargetInstrInfo.h (original)
+++ llvm/trunk/include/llvm/Target/TargetInstrInfo.h Thu Aug 5 20:32:48 2010
@@ -576,6 +576,21 @@
/// register allocation.
virtual ScheduleHazardRecognizer*
CreateTargetPostRAHazardRecognizer(const InstrItineraryData&) const = 0;
+
+ /// isCompareInstr - If the machine instruction is a comparison instruction,
+ /// then return true. Also return the source register in SrcReg and the value
+ /// it compares against in CmpValue.
+ virtual bool isCompareInstr(const MachineInstr *MI,
+ unsigned &SrcReg, int &CmpValue) const {
+ return false;
+ }
+
+ /// convertToSetZeroFlag - Convert the instruction to set the zero flag so
+ /// that we can remove a "comparison with zero".
+ virtual bool convertToSetZeroFlag(MachineInstr *Instr,
+ MachineInstr *CmpInstr) const {
+ return false;
+ }
};
/// TargetInstrInfoImpl - This is the default implementation of
Modified: llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp?rev=110423&r1=110422&r2=110423&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp (original)
+++ llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp Thu Aug 5 20:32:48 2010
@@ -354,6 +354,7 @@
printAndVerify(PM, "After codegen DCE pass");
PM.add(createOptimizeExtsPass());
+ PM.add(createOptimizeCmpsPass());
if (!DisableMachineLICM)
PM.add(createMachineLICMPass());
PM.add(createMachineCSEPass());
Added: llvm/trunk/lib/CodeGen/OptimizeCmps.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/OptimizeCmps.cpp?rev=110423&view=auto
==============================================================================
--- llvm/trunk/lib/CodeGen/OptimizeCmps.cpp (added)
+++ llvm/trunk/lib/CodeGen/OptimizeCmps.cpp Thu Aug 5 20:32:48 2010
@@ -0,0 +1,112 @@
+//===-- OptimizeCmps.cpp - Optimize comparison instrs ---------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass performs optimization of comparison instructions. For instance, in
+// this code:
+//
+// sub r1, 1
+// cmp r1, 0
+// bz L1
+//
+// If the "sub" instruction all ready sets (or could be modified to set) the
+// same flag that the "cmp" instruction sets and that "bz" uses, then we can
+// eliminate the "cmp" instruction.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "opt-compares"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/ADT/Statistic.h"
+using namespace llvm;
+
+STATISTIC(NumEliminated, "Number of compares eliminated");
+
+static cl::opt<bool>
+EnableOptCmps("enable-optimize-cmps", cl::init(false), cl::Hidden);
+
+namespace {
+ class OptimizeCmps : public MachineFunctionPass {
+ const TargetMachine *TM;
+ const TargetInstrInfo *TII;
+ MachineRegisterInfo *MRI;
+
+ bool OptimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB);
+
+ public:
+ static char ID; // Pass identification
+ OptimizeCmps() : MachineFunctionPass(&ID) {}
+
+ virtual bool runOnMachineFunction(MachineFunction &MF);
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+ MachineFunctionPass::getAnalysisUsage(AU);
+ }
+ };
+}
+
+char OptimizeCmps::ID = 0;
+INITIALIZE_PASS(OptimizeCmps, "opt-cmps",
+ "Optimize comparison instrs", false, false);
+
+FunctionPass *llvm::createOptimizeCmpsPass() { return new OptimizeCmps(); }
+
+/// OptimizeCmpInstr - If the instruction is a compare and the previous
+/// instruction it's comparing against all ready sets (or could be modified to
+/// set) the same flag as the compare, then we can remove the comparison and use
+/// the flag from the previous instruction.
+bool OptimizeCmps::OptimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB) {
+ // If this instruction is a comparison against zero and isn't comparing a
+ // physical register, we can try to optimize it.
+ unsigned SrcReg;
+ int CmpValue;
+ if (!TII->isCompareInstr(MI, SrcReg, CmpValue) ||
+ TargetRegisterInfo::isPhysicalRegister(SrcReg) ||
+ CmpValue != 0)
+ return false;
+
+ MachineRegisterInfo::def_iterator DI = MRI->def_begin(SrcReg);
+ if (llvm::next(DI) != MRI->def_end())
+ // Only support one definition.
+ return false;
+
+ // Attempt to convert the defining instruction to set the "zero" flag.
+ if (TII->convertToSetZeroFlag(&*DI, MI)) {
+ ++NumEliminated;
+ return true;
+ }
+
+ return false;
+}
+
+bool OptimizeCmps::runOnMachineFunction(MachineFunction &MF) {
+ TM = &MF.getTarget();
+ TII = TM->getInstrInfo();
+ MRI = &MF.getRegInfo();
+
+ if (!EnableOptCmps) return false;
+
+ bool Changed = false;
+ for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
+ MachineBasicBlock *MBB = &*I;
+ for (MachineBasicBlock::iterator
+ MII = MBB->begin(), ME = MBB->end(); MII != ME; ) {
+ MachineInstr *MI = &*MII++;
+ Changed |= OptimizeCmpInstr(MI, MBB);
+ }
+ }
+
+ return Changed;
+}
Modified: llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.cpp?rev=110423&r1=110422&r2=110423&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.cpp Thu Aug 5 20:32:48 2010
@@ -1353,3 +1353,59 @@
Offset = (isSub) ? -Offset : Offset;
return Offset == 0;
}
+
+bool ARMBaseInstrInfo::
+isCompareInstr(const MachineInstr *MI, unsigned &SrcReg, int &CmpValue) const {
+ switch (MI->getOpcode()) {
+ default: break;
+ case ARM::t2CMPri:
+ case ARM::t2CMPzri:
+ SrcReg = MI->getOperand(0).getReg();
+ CmpValue = MI->getOperand(1).getImm();
+ return true;
+ }
+
+ return false;
+}
+
+/// convertToSetZeroFlag - Convert the instruction to set the "zero" flag so
+/// that we can remove a "comparison with zero".
+bool ARMBaseInstrInfo::
+convertToSetZeroFlag(MachineInstr *MI, MachineInstr *CmpInstr) const {
+ // Conservatively refuse to convert an instruction which isn't in the same BB
+ // as the comparison.
+ if (MI->getParent() != CmpInstr->getParent())
+ return false;
+
+ // Check that CPSR isn't set between the comparison instruction and the one we
+ // want to change.
+ MachineBasicBlock::const_iterator I = CmpInstr, E = MI;
+ --I;
+ for (; I != E; --I) {
+ const MachineInstr &Instr = *I;
+
+ for (unsigned IO = 0, EO = Instr.getNumOperands(); IO != EO; ++IO) {
+ const MachineOperand &MO = Instr.getOperand(IO);
+ if (!MO.isDef() || !MO.isReg()) continue;
+
+ // This instruction modifies CPSR before the one we want to change. We
+ // can't do this transformation.
+ if (MO.getReg() == ARM::CPSR)
+ return false;
+ }
+ }
+
+ // Set the "zero" bit in CPSR.
+ switch (MI->getOpcode()) {
+ default: break;
+ case ARM::t2SUBri: {
+ MI->RemoveOperand(5);
+ MachineInstrBuilder MB(MI);
+ MB.addReg(ARM::CPSR, RegState::Define | RegState::Implicit);
+ CmpInstr->eraseFromParent();
+ return true;
+ }
+ }
+
+ return false;
+}
Modified: llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.h?rev=110423&r1=110422&r2=110423&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.h (original)
+++ llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.h Thu Aug 5 20:32:48 2010
@@ -336,6 +336,17 @@
unsigned NumInstrs) const {
return NumInstrs && NumInstrs == 1;
}
+
+ /// isCompareInstr - If the machine instruction is a comparison instruction,
+ /// then return true. Also return the source register in SrcReg and the value
+ /// it compares against in CmpValue.
+ virtual bool isCompareInstr(const MachineInstr *MI, unsigned &SrcReg,
+ int &CmpValue) const;
+
+ /// convertToSetZeroFlag - Convert the instruction to set the zero flag so
+ /// that we can remove a "comparison with zero".
+ virtual bool convertToSetZeroFlag(MachineInstr *Instr,
+ MachineInstr *CmpInstr) const;
};
static inline
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