[llvm] [SPIR-V] Preserve available_externally linkage via NonSemantic.AuxData (PR #200002)

[Nick Sarnie via llvm-commits]

================
@@ -0,0 +1,123 @@
+//===-- SPIRVAuxDataHandler.cpp - NonSemantic.AuxData emitter -*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "SPIRVAuxDataHandler.h"
+#include "MCTargetDesc/SPIRVMCTargetDesc.h"
+#include "SPIRVSubtarget.h"
+#include "SPIRVUtils.h"
+#include "llvm/CodeGen/AsmPrinter.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Module.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCStreamer.h"
+
+using namespace llvm;
+
+namespace {
+constexpr int64_t AuxDataLinkage = 4;
+constexpr uint32_t LinkageAvailableExternally = 0;
+} // namespace
+
+SPIRVAuxDataHandler::SPIRVAuxDataHandler(AsmPrinter &AP, const Module &M)
+    : Asm(AP) {
+  for (const Function &F : M)
+    if (F.hasFnAttribute(SPIRV_WAS_AVAILABLE_EXTERNALLY_ATTR))
+      LinkagePreservedFns.push_back(&F);
+}
+
+void SPIRVAuxDataHandler::prepareModuleOutput(const SPIRVSubtarget &ST,
+                                              SPIRV::ModuleAnalysisInfo &MAI) {
+  if (LinkagePreservedFns.empty())
+    return;
+  if (!ST.canUseExtension(SPIRV::Extension::SPV_KHR_non_semantic_info))
+    return;
+  MAI.Reqs.addExtension(SPIRV::Extension::SPV_KHR_non_semantic_info);
+  constexpr unsigned AuxSet =
+      static_cast<unsigned>(SPIRV::InstructionSet::NonSemantic_AuxData);
+  if (!MAI.ExtInstSetMap.count(AuxSet))
+    MAI.ExtInstSetMap[AuxSet] = MAI.getNextIDRegister();
+}
+
+void SPIRVAuxDataHandler::emitAuxData(SPIRV::ModuleAnalysisInfo &MAI) {
+  if (LinkagePreservedFns.empty())
+    return;
+  constexpr unsigned AuxSet =
+      static_cast<unsigned>(SPIRV::InstructionSet::NonSemantic_AuxData);
+  MCRegister ExtSetReg = MAI.getExtInstSetReg(AuxSet);
+  if (!ExtSetReg.isValid())
+    return;
+
+  MCRegister VoidTypeReg = findOrEmitOpTypeVoid(MAI);
+  MCRegister I32TypeReg = findOrEmitOpTypeInt32(MAI);
+  // Share one OpConstant across all AE functions.
+  MCRegister ZeroReg;
+
+  for (const Function *F : LinkagePreservedFns) {
+    MCRegister FnReg = MAI.getGlobalObjReg(F);
+    if (!FnReg.isValid())
+      continue;
+    if (!ZeroReg.isValid())
+      ZeroReg = emitOpConstantI32(LinkageAvailableExternally, I32TypeReg, MAI);
+    MCRegister ValReg = ZeroReg;
+    MCInst Inst;
+    Inst.setOpcode(SPIRV::OpExtInst);
+    Inst.addOperand(MCOperand::createReg(MAI.getNextIDRegister()));
+    Inst.addOperand(MCOperand::createReg(VoidTypeReg));
+    Inst.addOperand(MCOperand::createReg(ExtSetReg));
+    Inst.addOperand(MCOperand::createImm(AuxDataLinkage));
+    Inst.addOperand(MCOperand::createReg(FnReg));
+    Inst.addOperand(MCOperand::createReg(ValReg));
+    emitMCInst(Inst);
+  }
+}
+
+void SPIRVAuxDataHandler::emitMCInst(MCInst &Inst) {
+  Asm.OutStreamer->emitInstruction(Inst, Asm.getSubtargetInfo());
+}
+
+MCRegister
+SPIRVAuxDataHandler::findOrEmitOpTypeVoid(SPIRV::ModuleAnalysisInfo &MAI) {
+  for (const MachineInstr *MI : MAI.getMSInstrs(SPIRV::MB_TypeConstVars))
+    if (MI->getOpcode() == SPIRV::OpTypeVoid)
+      return MAI.getRegisterAlias(MI->getMF(), MI->getOperand(0).getReg());
+  MCRegister Reg = MAI.getNextIDRegister();
+  MCInst Inst;
+  Inst.setOpcode(SPIRV::OpTypeVoid);
+  Inst.addOperand(MCOperand::createReg(Reg));
+  emitMCInst(Inst);
+  return Reg;
+}
+
+MCRegister
+SPIRVAuxDataHandler::findOrEmitOpTypeInt32(SPIRV::ModuleAnalysisInfo &MAI) {
+  for (const MachineInstr *MI : MAI.getMSInstrs(SPIRV::MB_TypeConstVars))
+    if (MI->getOpcode() == SPIRV::OpTypeInt &&
+        MI->getOperand(1).getImm() == 32 && MI->getOperand(2).getImm() == 0)
----------------
sarnex wrote:

might help to break out the operands into seperate vars so the var names can provide clarity as to what they are

https://github.com/llvm/llvm-project/pull/200002