[llvm] [X86][GISEL] Enable PostLegalize Combiner (PR #174696)

[Evgenii Kudriashov via llvm-commits]

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@@ -0,0 +1,189 @@
+//=== X86PostLegalizerCombiner.cpp --------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Post-legalization combines on generic MachineInstrs.
+///
+/// The combines here must preserve instruction legality.
+///
+/// Lowering combines (e.g. pseudo matching) should be handled by
+/// X86PostLegalizerLowering.
+///
+/// Combines which don't rely on instruction legality should go in the
+/// X86PreLegalizerCombiner.
+///
+//===----------------------------------------------------------------------===//
+#include "X86.h"
+#include "X86TargetMachine.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/CodeGen/GlobalISel/CSEInfo.h"
+#include "llvm/CodeGen/GlobalISel/CSEMIRBuilder.h"
+#include "llvm/CodeGen/GlobalISel/Combiner.h"
+#include "llvm/CodeGen/GlobalISel/CombinerHelper.h"
+#include "llvm/CodeGen/GlobalISel/CombinerInfo.h"
+#include "llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h"
+#include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h"
+#include "llvm/CodeGen/GlobalISel/GISelValueTracking.h"
+#include "llvm/CodeGen/GlobalISel/GenericMachineInstrs.h"
+#include "llvm/CodeGen/GlobalISel/MIPatternMatch.h"
+#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
+#include "llvm/CodeGen/GlobalISel/Utils.h"
+#include "llvm/CodeGen/MachineDominators.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/TargetOpcodes.h"
+#include "llvm/CodeGen/TargetPassConfig.h"
+#include "llvm/Support/Debug.h"
+
+#define GET_GICOMBINER_DEPS
+#include "X86GenPostLegalizeGICombiner.inc"
+#undef GET_GICOMBINER_DEPS
+
+#define DEBUG_TYPE "X86-postlegalizer-combiner"
+
+using namespace llvm;
+using namespace MIPatternMatch;
+
+namespace {
+
+#define GET_GICOMBINER_TYPES
+#include "X86GenPostLegalizeGICombiner.inc"
+#undef GET_GICOMBINER_TYPES
+
+class X86PostLegalizerCombinerImpl : public Combiner {
+protected:
+  const CombinerHelper Helper;
+  const X86PostLegalizerCombinerImplRuleConfig &RuleConfig;
+  const X86Subtarget &STI;
+
+public:
+  X86PostLegalizerCombinerImpl(
+      MachineFunction &MF, CombinerInfo &CInfo, const TargetPassConfig *TPC,
+      GISelValueTracking &VT, GISelCSEInfo *CSEInfo,
+      const X86PostLegalizerCombinerImplRuleConfig &RuleConfig,
+      const X86Subtarget &STI, MachineDominatorTree *MDT,
+      const LegalizerInfo *LI);
+
+  static const char *getName() { return "X86PostLegalizerCombiner"; }
+
+  bool tryCombineAll(MachineInstr &I) const override;
+  bool tryCombineAllImpl(MachineInstr &I) const;
+
+private:
+#define GET_GICOMBINER_CLASS_MEMBERS
+#include "X86GenPostLegalizeGICombiner.inc"
+#undef GET_GICOMBINER_CLASS_MEMBERS
+};
+
+#define GET_GICOMBINER_IMPL
+#include "X86GenPostLegalizeGICombiner.inc"
+#undef GET_GICOMBINER_IMPL
+
+X86PostLegalizerCombinerImpl::X86PostLegalizerCombinerImpl(
+    MachineFunction &MF, CombinerInfo &CInfo, const TargetPassConfig *TPC,
+    GISelValueTracking &VT, GISelCSEInfo *CSEInfo,
+    const X86PostLegalizerCombinerImplRuleConfig &RuleConfig,
+    const X86Subtarget &STI, MachineDominatorTree *MDT, const LegalizerInfo *LI)
+    : Combiner(MF, CInfo, TPC, &VT, CSEInfo),
+      Helper(Observer, B, /*IsPreLegalize*/ false, &VT, MDT, LI),
+      RuleConfig(RuleConfig), STI(STI),
+#define GET_GICOMBINER_CONSTRUCTOR_INITS
+#include "X86GenPostLegalizeGICombiner.inc"
+#undef GET_GICOMBINER_CONSTRUCTOR_INITS
+{
+}
+
+bool X86PostLegalizerCombinerImpl::tryCombineAll(MachineInstr &MI) const {
+  return tryCombineAllImpl(MI);
+}
+
+class X86PostLegalizerCombiner : public MachineFunctionPass {
+public:
+  static char ID;
+
+  X86PostLegalizerCombiner();
+
+  StringRef getPassName() const override { return "X86PostLegalizerCombiner"; }
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+private:
+  X86PostLegalizerCombinerImplRuleConfig RuleConfig;
+};
+} // end anonymous namespace
+
+void X86PostLegalizerCombiner::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.addRequired<TargetPassConfig>();
+  AU.setPreservesCFG();
+  getSelectionDAGFallbackAnalysisUsage(AU);
+  AU.addRequired<GISelValueTrackingAnalysisLegacy>();
+  AU.addPreserved<GISelValueTrackingAnalysisLegacy>();
+  // This is only added when processing level is not OptNone.
+  AU.addRequired<MachineDominatorTreeWrapperPass>();
+  AU.addPreserved<MachineDominatorTreeWrapperPass>();
+  AU.addRequired<GISelCSEAnalysisWrapperPass>();
+  AU.addPreserved<GISelCSEAnalysisWrapperPass>();
+
+  MachineFunctionPass::getAnalysisUsage(AU);
+}
+
+X86PostLegalizerCombiner::X86PostLegalizerCombiner() : MachineFunctionPass(ID) {
+  if (!RuleConfig.parseCommandLineOption())
+    report_fatal_error("Invalid rule identifier");
+}
+
+bool X86PostLegalizerCombiner::runOnMachineFunction(MachineFunction &MF) {
+  if (MF.getProperties().hasFailedISel())
+    return false;
+  assert(MF.getProperties().hasLegalized() && "Expected a legalized function?");
+  auto *TPC = &getAnalysis<TargetPassConfig>();
+  const Function &F = MF.getFunction();
+  bool EnableOpt =
+      MF.getTarget().getOptLevel() != CodeGenOptLevel::None && !skipFunction(F);
+
+  const X86Subtarget &ST = MF.getSubtarget<X86Subtarget>();
+  const auto *LI = ST.getLegalizerInfo();
+
+  GISelValueTracking *VT =
+      &getAnalysis<GISelValueTrackingAnalysisLegacy>().get(MF);
+  MachineDominatorTree *MDT =
+      &getAnalysis<MachineDominatorTreeWrapperPass>().getDomTree();
+  GISelCSEAnalysisWrapper &Wrapper =
+      getAnalysis<GISelCSEAnalysisWrapperPass>().getCSEWrapper();
+  auto *CSEInfo = &Wrapper.get(TPC->getCSEConfig());
+
+  CombinerInfo CInfo(/*AllowIllegalOps*/ true, /*ShouldLegalizeIllegal*/ false,
+                     /*LegalizerInfo*/ nullptr, EnableOpt, F.hasOptSize(),
+                     F.hasMinSize());
+  // Disable fixed-point iteration to reduce compile-time
+  CInfo.MaxIterations = 1;
+  CInfo.ObserverLvl = CombinerInfo::ObserverLevel::SinglePass;
+  // Legalizer performs DCE, so a full DCE pass is unnecessary.
+  CInfo.EnableFullDCE = false;
+  X86PostLegalizerCombinerImpl Impl(MF, CInfo, TPC, *VT, CSEInfo, RuleConfig,
+                                    ST, MDT, LI);
+  bool Changed = Impl.combineMachineInstrs();
+  return Changed;
----------------
e-kud wrote:

```suggestion
  return Impl.combineMachineInstrs();
```

https://github.com/llvm/llvm-project/pull/174696