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/*========================== begin_copyright_notice ============================
Copyright (C) 2022 Intel Corporation
SPDX-License-Identifier: MIT
============================= end_copyright_notice ===========================*/
//===----------------------------------------------------------------------===//
//
/// GenXCloneIndirectFunctions
/// --------------------------
///
/// VISA has a restriction that a function can be called either directly or
/// indirectly but a combination of these two methods are not permitted for a
/// single function. This restriction rises two problems that this pass solves:
///
/// 1. We do not know all call instructions of an extern function until final
/// linkage happens. Hence all the unknown call of the function is thought to be
/// always indirect. But the function's module can contain direct calls to it
/// that's why we create a clone function:
/// * Original function linkage type is set to external as it is expected to
/// be called indirectly;
/// * A function with external linkage type and the name of the original
/// function with "direct" suffix is created. This is a copy of the original
/// function.
/// Thus, direct calls and indirect ones are separated and all unknown possible
/// calls from other modules will original function without any need to change
/// something on their side.
///
/// Before:
///
/// direct calls --> |
/// | --> external foo()
/// indirect calls --> |
///
/// After:
/// clone function
/// |
/// v
/// direct calls --> internal foo_direct()
/// indirect calls --> external foo()
/// ^
/// |
/// original function
///
/// 2. An internal function can also be called directly and indirectly inside a
/// module. The idea is the same: an internal clone function is created,
/// and the calls are separated.
///
//===----------------------------------------------------------------------===//
#include "llvmWrapper/IR/Value.h"
#include "vc/GenXOpts/GenXOpts.h"
#include "vc/InternalIntrinsics/InternalIntrinsics.h"
#include "vc/Support/BackendConfig.h"
#include "vc/Utils/GenX/Intrinsics.h"
#include "vc/Utils/GenX/KernelInfo.h"
#include <llvm/GenXIntrinsics/GenXIntrinsics.h>
#include <llvm/IR/InstVisitor.h>
#include <llvm/InitializePasses.h>
#include <llvm/Pass.h>
#include <llvm/Support/CommandLine.h>
#include <llvm/Support/Debug.h>
#include <llvm/Transforms/Utils/Cloning.h>
using namespace llvm;
static cl::opt<bool> EnableCloneIndirectFunctions(
"vc-enable-clone-indirect-functions",
llvm::cl::desc("Enable/disable GenXCloneIndirectFunctions"), cl::init(true),
cl::Hidden);
namespace {
class GenXCloneIndirectFunctions
: public ModulePass,
public InstVisitor<GenXCloneIndirectFunctions> {
std::vector<std::pair<Function *, bool>> IndirectFuncs;
public:
static char ID;
GenXCloneIndirectFunctions() : ModulePass(ID) {
initializeGenXCloneIndirectFunctionsPass(*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<GenXBackendConfig>();
}
StringRef getPassName() const override {
return "GenXCloneIndirectFunctions";
}
bool runOnModule(Module &M) override;
void visitFunction(Function &F);
};
} // namespace
void GenXCloneIndirectFunctions::visitFunction(Function &F) {
if (GenXIntrinsic::isAnyNonTrivialIntrinsic(&F))
return;
if (vc::InternalIntrinsic::isInternalNonTrivialIntrinsic(&F))
return;
if (vc::isEmulationFunction(F))
return;
if (vc::isKernel(&F))
return;
if (vc::isCMCallable(F))
return;
if (!F.hasLocalLinkage()) {
IndirectFuncs.emplace_back(&F, true);
return;
}
IGC_ASSERT_MESSAGE(!F.isDeclaration(), "Declaration with local linkage?");
if (F.hasAddressTaken())
IndirectFuncs.emplace_back(&F, false);
}
static void cloneIndirectFunction(Function &F,
GlobalValue::LinkageTypes IndirectLinkage) {
// Clone the function F for direct calls
ValueToValueMapTy VMap;
auto *Direct = CloneFunction(&F, VMap);
Direct->setName(F.getName() + "_direct");
Direct->setLinkage(GlobalValue::InternalLinkage);
// Replace all uses of the original function that are direct calls.
IGCLLVM::replaceUsesWithIf(&F, Direct, [&F](Use &U) {
auto *CI = dyn_cast<CallInst>(U.getUser());
return CI && CI->getCalledFunction() == &F;
});
// Original function is an indirect stack call
if (!vc::requiresStackCall(&F))
F.addFnAttr(genx::FunctionMD::CMStackCall);
}
bool GenXCloneIndirectFunctions::runOnModule(Module &M) {
if (!EnableCloneIndirectFunctions)
return false;
auto &&BECfg = getAnalysis<GenXBackendConfig>();
IGC_ASSERT_MESSAGE(
llvm::none_of(M.functions(),
[&](const Function& F) { return F.hasAddressTaken() && BECfg.directCallsOnly(F.getName()); }),
"A function has address taken inside the module that contradicts "
"DirectCallsOnly option");
// If direct calls are forced for all functions.
if (BECfg.directCallsOnly()) {
return false;
}
visit(M);
bool Modified = false;
for (auto [F, IsExternal] : IndirectFuncs) {
if (BECfg.directCallsOnly(F->getName())) continue;
auto CheckDirectCall = [Func = F](User *U) {
auto *CI = dyn_cast<CallInst>(U);
return CI && CI->getCalledFunction() == Func;
};
if (F->isDeclaration()) {
IGC_ASSERT_MESSAGE(IsExternal,
"Internal-linkage function cannot be a declaration");
if (!vc::requiresStackCall(F)) {
F->addFnAttr(genx::FunctionMD::CMStackCall);
Modified = true;
}
IGC_ASSERT_MESSAGE(vc::isIndirect(F) || F->hasExternalLinkage(),
"Must be indirect");
} else if (llvm::any_of(F->users(), CheckDirectCall)) {
cloneIndirectFunction(*F, IsExternal ? GlobalValue::ExternalLinkage
: GlobalValue::InternalLinkage);
Modified = true;
} else {
// If the function is not called directly, there is no need to clone
if (!vc::requiresStackCall(F)) {
F->addFnAttr(genx::FunctionMD::CMStackCall);
Modified = true;
}
}
IGC_ASSERT_MESSAGE(vc::isIndirect(F), "Must be indirect");
}
IndirectFuncs.clear();
return Modified;
}
char GenXCloneIndirectFunctions::ID = 0;
INITIALIZE_PASS_BEGIN(GenXCloneIndirectFunctions, "GenXCloneIndirectFunctions",
"GenXCloneIndirectFunctions", false, false)
INITIALIZE_PASS_DEPENDENCY(GenXBackendConfig)
INITIALIZE_PASS_END(GenXCloneIndirectFunctions, "GenXCloneIndirectFunctions",
"GenXCloneIndirectFunctions", false, false)
ModulePass *llvm::createGenXCloneIndirectFunctionsPass() {
return new GenXCloneIndirectFunctions();
}
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