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//===-- AMDGPURemoveIncompatibleFunctions.cpp -----------------------------===//
//
// 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
/// This pass replaces all uses of functions that use GPU features
/// incompatible with the current GPU with null then deletes the function.
//
//===----------------------------------------------------------------------===//
#include "AMDGPU.h"
#include "GCNSubtarget.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Target/TargetMachine.h"
#define DEBUG_TYPE "amdgpu-remove-incompatible-functions"
using namespace llvm;
namespace llvm {
extern const SubtargetFeatureKV
AMDGPUFeatureKV[AMDGPU::NumSubtargetFeatures - 1];
}
namespace {
using Generation = AMDGPUSubtarget::Generation;
class AMDGPURemoveIncompatibleFunctions : public ModulePass {
public:
static char ID;
AMDGPURemoveIncompatibleFunctions(const TargetMachine *TM = nullptr)
: ModulePass(ID), TM(TM) {
assert(TM && "No TargetMachine!");
}
StringRef getPassName() const override {
return "AMDGPU Remove Incompatible Functions";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {}
/// Checks a single function, returns true if the function must be deleted.
bool checkFunction(Function &F);
bool runOnModule(Module &M) override {
assert(TM->getTargetTriple().isAMDGCN());
SmallVector<Function *, 4> FnsToDelete;
for (Function &F : M) {
if (checkFunction(F))
FnsToDelete.push_back(&F);
}
for (Function *F : FnsToDelete) {
F->replaceAllUsesWith(ConstantPointerNull::get(F->getType()));
F->eraseFromParent();
}
return !FnsToDelete.empty();
}
private:
const TargetMachine *TM = nullptr;
};
StringRef getFeatureName(unsigned Feature) {
for (const SubtargetFeatureKV &KV : AMDGPUFeatureKV)
if (Feature == KV.Value)
return KV.Key;
llvm_unreachable("Unknown Target feature");
}
const SubtargetSubTypeKV *getGPUInfo(const GCNSubtarget &ST,
StringRef GPUName) {
for (const SubtargetSubTypeKV &KV : ST.getAllProcessorDescriptions())
if (StringRef(KV.Key) == GPUName)
return &KV;
return nullptr;
}
constexpr unsigned FeaturesToCheck[] = {
AMDGPU::FeatureGFX11Insts, AMDGPU::FeatureGFX10Insts,
AMDGPU::FeatureGFX9Insts, AMDGPU::FeatureGFX8Insts,
AMDGPU::FeatureDPP, AMDGPU::Feature16BitInsts,
AMDGPU::FeatureDot1Insts, AMDGPU::FeatureDot2Insts,
AMDGPU::FeatureDot3Insts, AMDGPU::FeatureDot4Insts,
AMDGPU::FeatureDot5Insts, AMDGPU::FeatureDot6Insts,
AMDGPU::FeatureDot7Insts, AMDGPU::FeatureDot8Insts,
};
FeatureBitset expandImpliedFeatures(const FeatureBitset &Features) {
FeatureBitset Result = Features;
for (const SubtargetFeatureKV &FE : AMDGPUFeatureKV) {
if (Features.test(FE.Value) && FE.Implies.any())
Result |= expandImpliedFeatures(FE.Implies.getAsBitset());
}
return Result;
}
void reportFunctionRemoved(Function &F, unsigned Feature) {
OptimizationRemarkEmitter ORE(&F);
ORE.emit([&]() {
// Note: we print the function name as part of the diagnostic because if
// debug info is not present, users get "<unknown>:0:0" as the debug
// loc. If we didn't print the function name there would be no way to
// tell which function got removed.
return OptimizationRemark(DEBUG_TYPE, "AMDGPUIncompatibleFnRemoved", &F)
<< "removing function '" << F.getName() << "': +"
<< getFeatureName(Feature)
<< " is not supported on the current target";
});
return;
}
} // end anonymous namespace
bool AMDGPURemoveIncompatibleFunctions::checkFunction(Function &F) {
if (F.isDeclaration())
return false;
const GCNSubtarget *ST =
static_cast<const GCNSubtarget *>(TM->getSubtargetImpl(F));
// Check the GPU isn't generic. Generic is used for testing only
// and we don't want this pass to interfere with it.
StringRef GPUName = ST->getCPU();
if (GPUName.empty() || GPUName.contains("generic"))
return false;
// Try to fetch the GPU's info. If we can't, it's likely an unknown processor
// so just bail out.
const SubtargetSubTypeKV *GPUInfo = getGPUInfo(*ST, GPUName);
if (!GPUInfo)
return false;
// Get all the features implied by the current GPU, and recursively expand
// the features that imply other features.
//
// e.g. GFX90A implies FeatureGFX9, and FeatureGFX9 implies a whole set of
// other features.
const FeatureBitset GPUFeatureBits =
expandImpliedFeatures(GPUInfo->Implies.getAsBitset());
// Now that the have a FeatureBitset containing all possible features for
// the chosen GPU, check our list of "suspicious" features.
// Check that the user didn't enable any features that aren't part of that
// GPU's feature set. We only check a predetermined set of features.
for (unsigned Feature : FeaturesToCheck) {
if (ST->hasFeature(Feature) && !GPUFeatureBits.test(Feature)) {
reportFunctionRemoved(F, Feature);
return true;
}
}
// Delete FeatureWavefrontSize32 functions for
// gfx9 and below targets that don't support the mode.
// gfx10+ is implied to support both wave32 and 64 features.
// They are not in the feature set. So, we need a separate check
if (ST->getGeneration() < AMDGPUSubtarget::GFX10 &&
ST->hasFeature(AMDGPU::FeatureWavefrontSize32)) {
reportFunctionRemoved(F, AMDGPU::FeatureWavefrontSize32);
return true;
}
return false;
}
INITIALIZE_PASS(AMDGPURemoveIncompatibleFunctions, DEBUG_TYPE,
"AMDGPU Remove Incompatible Functions", false, false)
char AMDGPURemoveIncompatibleFunctions::ID = 0;
ModulePass *
llvm::createAMDGPURemoveIncompatibleFunctionsPass(const TargetMachine *TM) {
return new AMDGPURemoveIncompatibleFunctions(TM);
}
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