[PowerPC] Convert r+r instructions to r+i (pre and post RA)
This patch adds the necessary infrastructure to convert instructions that
take two register operands to those that take a register and immediate if
the necessary operand is produced by a load-immediate. Furthermore, it uses
this infrastructure to perform such conversions twice - first at MachineSSA
and then pre-emit.
There are a number of reasons we may end up with opportunities for this
transformation, including but not limited to:
- X-Form instructions chosen since the exact offset isn't available at ISEL time
- Atomic instructions with constant operands (we will add patterns for this
in the future)
- Tail duplication may duplicate code where one block contains this redundancy
- When emitting compare-free code in PPCDAGToDAGISel, we don't handle constant
comparands specially
Furthermore, this patch moves the initialization of PPCMIPeepholePass so that
it can be used for MIR tests.
llvm-svn: 320791
diff --git a/llvm/lib/Target/PowerPC/PPCPreEmitPeephole.cpp b/llvm/lib/Target/PowerPC/PPCPreEmitPeephole.cpp
new file mode 100644
index 0000000..df0e9f3
--- /dev/null
+++ b/llvm/lib/Target/PowerPC/PPCPreEmitPeephole.cpp
@@ -0,0 +1,95 @@
+//===--------- PPCPreEmitPeephole.cpp - Late peephole optimizations -------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// A pre-emit peephole for catching opportunities introduced by late passes such
+// as MachineBlockPlacement.
+//
+//===----------------------------------------------------------------------===//
+
+#include "PPC.h"
+#include "PPCInstrInfo.h"
+#include "PPCSubtarget.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/LivePhysRegs.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/Debug.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "ppc-pre-emit-peephole"
+
+STATISTIC(NumRRConvertedInPreEmit,
+ "Number of r+r instructions converted to r+i in pre-emit peephole");
+STATISTIC(NumRemovedInPreEmit,
+ "Number of instructions deleted in pre-emit peephole");
+
+static cl::opt<bool>
+RunPreEmitPeephole("ppc-late-peephole", cl::Hidden, cl::init(true),
+ cl::desc("Run pre-emit peephole optimizations."));
+
+namespace {
+ class PPCPreEmitPeephole : public MachineFunctionPass {
+ public:
+ static char ID;
+ PPCPreEmitPeephole() : MachineFunctionPass(ID) {
+ initializePPCPreEmitPeepholePass(*PassRegistry::getPassRegistry());
+ }
+
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ MachineFunctionPass::getAnalysisUsage(AU);
+ }
+
+ MachineFunctionProperties getRequiredProperties() const override {
+ return MachineFunctionProperties().set(
+ MachineFunctionProperties::Property::NoVRegs);
+ }
+
+ bool runOnMachineFunction(MachineFunction &MF) override {
+ if (skipFunction(*MF.getFunction()) || !RunPreEmitPeephole)
+ return false;
+ bool Changed = false;
+ const PPCInstrInfo *TII = MF.getSubtarget<PPCSubtarget>().getInstrInfo();
+ SmallVector<MachineInstr *, 4> InstrsToErase;
+ for (MachineBasicBlock &MBB : MF) {
+ for (MachineInstr &MI : MBB) {
+ MachineInstr *DefMIToErase = nullptr;
+ if (TII->convertToImmediateForm(MI, &DefMIToErase)) {
+ Changed = true;
+ NumRRConvertedInPreEmit++;
+ DEBUG(dbgs() << "Converted instruction to imm form: ");
+ DEBUG(MI.dump());
+ if (DefMIToErase) {
+ InstrsToErase.push_back(DefMIToErase);
+ }
+ }
+ }
+ }
+ for (MachineInstr *MI : InstrsToErase) {
+ DEBUG(dbgs() << "PPC pre-emit peephole: erasing instruction: ");
+ DEBUG(MI->dump());
+ MI->eraseFromParent();
+ NumRemovedInPreEmit++;
+ }
+ return Changed;
+ }
+ };
+}
+
+INITIALIZE_PASS(PPCPreEmitPeephole, DEBUG_TYPE, "PowerPC Pre-Emit Peephole",
+ false, false)
+char PPCPreEmitPeephole::ID = 0;
+
+FunctionPass *llvm::createPPCPreEmitPeepholePass() {
+ return new PPCPreEmitPeephole();
+}