[SPIRV][SPIRVPrepareGlobals] Add pass skeleton

Add a pass where we can do IR->IR preprocessing of global-variables.

Author: jmmartinez

llvm/lib/Target/SPIRV/CMakeLists.txt

@@ -41,6 +41,7 @@ add_llvm_target(SPIRVCodeGen
   SPIRVPreLegalizerCombiner.cpp
   SPIRVPostLegalizer.cpp
   SPIRVPrepareFunctions.cpp
+  SPIRVPrepareGlobals.cpp
   SPIRVRegisterBankInfo.cpp
   SPIRVRegisterInfo.cpp
   SPIRVRegularizer.cpp

llvm/lib/Target/SPIRV/SPIRV.h

@@ -31,6 +31,7 @@ FunctionPass *createSPIRVPreLegalizerCombiner();
 FunctionPass *createSPIRVPreLegalizerPass();
 FunctionPass *createSPIRVPostLegalizerPass();
 ModulePass *createSPIRVEmitIntrinsicsPass(SPIRVTargetMachine *TM);
+ModulePass *createSPIRVPrepareGlobalsPass();
 MachineFunctionPass *createSPIRVEmitNonSemanticDIPass(SPIRVTargetMachine *TM);
 InstructionSelector *
 createSPIRVInstructionSelector(const SPIRVTargetMachine &TM,
@@ -51,6 +52,7 @@ void initializeSPIRVLegalizePointerCastPass(PassRegistry &);
 void initializeSPIRVRegularizerPass(PassRegistry &);
 void initializeSPIRVMergeRegionExitTargetsPass(PassRegistry &);
 void initializeSPIRVPrepareFunctionsPass(PassRegistry &);
+void initializeSPIRVPrepareGlobalsPass(PassRegistry &);
 void initializeSPIRVStripConvergentIntrinsicsPass(PassRegistry &);
 void initializeSPIRVLegalizeImplicitBindingPass(PassRegistry &);
 } // namespace llvm

llvm/lib/Target/SPIRV/SPIRVPrepareGlobals.cpp

@@ -0,0 +1,43 @@
+//===-- SPIRVPrepareGlobals.cpp - Prepare IR SPIRV globals ------*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+// The pass transforms IR globals that cannot be trivially mapped to SPIRV
+// into something that is trival to lower.
+//
+//===----------------------------------------------------------------------===//
+
+#include "SPIRV.h"
+
+using namespace llvm;
+
+namespace {
+
+struct SPIRVPrepareGlobals : public ModulePass {
+  static char ID;
+  SPIRVPrepareGlobals() : ModulePass(ID) {}
+
+  StringRef getPassName() const override {
+    return "SPIRV prepare global variables";
+  }
+
+  bool runOnModule(Module &M) override;
+};
+
+bool SPIRVPrepareGlobals::runOnModule(Module &M) { return false; }
+char SPIRVPrepareGlobals::ID = 0;
+
+} // namespace
+
+INITIALIZE_PASS(SPIRVPrepareGlobals, "prepare-globals",
+                "SPIRV prepare global variables", false, false)
+
+namespace llvm {
+ModulePass *createSPIRVPrepareGlobalsPass() {
+  return new SPIRVPrepareGlobals();
+}
+} // namespace llvm

llvm/lib/Target/SPIRV/SPIRVTargetMachine.cpp

@@ -59,6 +59,7 @@ extern "C" LLVM_ABI LLVM_EXTERNAL_VISIBILITY void LLVMInitializeSPIRVTarget() {
   initializeSPIRVEmitIntrinsicsPass(PR);
   initializeSPIRVEmitNonSemanticDIPass(PR);
   initializeSPIRVPrepareFunctionsPass(PR);
+  initializeSPIRVPrepareGlobalsPass(PR);
   initializeSPIRVStripConvergentIntrinsicsPass(PR);
 }
 
@@ -172,6 +173,7 @@ void SPIRVPassConfig::addIRPasses() {
 
   addPass(createSPIRVRegularizerPass());
   addPass(createSPIRVPrepareFunctionsPass(TM));
+  addPass(createSPIRVPrepareGlobalsPass());
 }
 
 void SPIRVPassConfig::addISelPrepare() {

llvm/test/CodeGen/SPIRV/llc-pipeline.ll

@@ -31,6 +31,7 @@
 ; SPIRV-O0-NEXT:      Expand reduction intrinsics
 ; SPIRV-O0-NEXT:      SPIR-V Regularizer
 ; SPIRV-O0-NEXT:    SPIRV prepare functions
+; SPIRV-O0-NEXT:    SPIRV prepare global variables
 ; SPIRV-O0-NEXT:    FunctionPass Manager
 ; SPIRV-O0-NEXT:      Lower invoke and unwind, for unwindless code generators
 ; SPIRV-O0-NEXT:      Remove unreachable blocks from the CFG
@@ -130,6 +131,7 @@
 ; SPIRV-Opt-NEXT:      Expand reduction intrinsics
 ; SPIRV-Opt-NEXT:      SPIR-V Regularizer
 ; SPIRV-Opt-NEXT:    SPIRV prepare functions
+; SPIRV-Opt-NEXT:    SPIRV prepare global variables
 ; SPIRV-Opt-NEXT:    FunctionPass Manager
 ; SPIRV-Opt-NEXT:      Dominator Tree Construction
 ; SPIRV-Opt-NEXT:      Natural Loop Information