mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-11-24 19:52:54 +01:00
76e5989934
We previously made a change to getUserCost to return a Invalid cost when one of the TTI costs returned '-1' (meaning 'unknown' or 'infinitely expensive'). It makes no sense to say that: shufflevector <2 x i8> %x, <2 x i8> %y, <4 x i32> <i32 0, i32 1, i32 2, i32 3> has an invalid cost. Perhaps the cost is not known, but the IR is valid and can be code-generated. Invalid should only be used for IR that cannot possibly be code-generated and where a cost is nonsensical. With more passes now asserting that the cost must be valid, it is possible that those assertions will fail for perfectly valid IR. An incomplete cost-model probably shouldn't be a reason for the compiler to break. It's better to consider these costs as 'very expensive' and ignore them for other reasons. At some point, we should consider replacing -1 with some other mechanism. Reviewed By: paulwalker-arm, dmgreen Differential Revision: https://reviews.llvm.org/D99502
116 lines
4.0 KiB
C++
116 lines
4.0 KiB
C++
//===- CostModel.cpp ------ Cost Model Analysis ---------------------------===//
|
|
//
|
|
// 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
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file defines the cost model analysis. It provides a very basic cost
|
|
// estimation for LLVM-IR. This analysis uses the services of the codegen
|
|
// to approximate the cost of any IR instruction when lowered to machine
|
|
// instructions. The cost results are unit-less and the cost number represents
|
|
// the throughput of the machine assuming that all loads hit the cache, all
|
|
// branches are predicted, etc. The cost numbers can be added in order to
|
|
// compare two or more transformation alternatives.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/ADT/STLExtras.h"
|
|
#include "llvm/Analysis/Passes.h"
|
|
#include "llvm/Analysis/TargetTransformInfo.h"
|
|
#include "llvm/IR/Function.h"
|
|
#include "llvm/InitializePasses.h"
|
|
#include "llvm/Pass.h"
|
|
#include "llvm/Support/CommandLine.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/Support/raw_ostream.h"
|
|
using namespace llvm;
|
|
|
|
static cl::opt<TargetTransformInfo::TargetCostKind> CostKind(
|
|
"cost-kind", cl::desc("Target cost kind"),
|
|
cl::init(TargetTransformInfo::TCK_RecipThroughput),
|
|
cl::values(clEnumValN(TargetTransformInfo::TCK_RecipThroughput,
|
|
"throughput", "Reciprocal throughput"),
|
|
clEnumValN(TargetTransformInfo::TCK_Latency,
|
|
"latency", "Instruction latency"),
|
|
clEnumValN(TargetTransformInfo::TCK_CodeSize,
|
|
"code-size", "Code size"),
|
|
clEnumValN(TargetTransformInfo::TCK_SizeAndLatency,
|
|
"size-latency", "Code size and latency")));
|
|
|
|
|
|
#define CM_NAME "cost-model"
|
|
#define DEBUG_TYPE CM_NAME
|
|
|
|
namespace {
|
|
class CostModelAnalysis : public FunctionPass {
|
|
|
|
public:
|
|
static char ID; // Class identification, replacement for typeinfo
|
|
CostModelAnalysis() : FunctionPass(ID), F(nullptr), TTI(nullptr) {
|
|
initializeCostModelAnalysisPass(
|
|
*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
/// Returns the expected cost of the instruction.
|
|
/// Returns -1 if the cost is unknown.
|
|
/// Note, this method does not cache the cost calculation and it
|
|
/// can be expensive in some cases.
|
|
InstructionCost getInstructionCost(const Instruction *I) const {
|
|
return TTI->getInstructionCost(I, TargetTransformInfo::TCK_RecipThroughput);
|
|
}
|
|
|
|
private:
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override;
|
|
bool runOnFunction(Function &F) override;
|
|
void print(raw_ostream &OS, const Module*) const override;
|
|
|
|
/// The function that we analyze.
|
|
Function *F;
|
|
/// Target information.
|
|
const TargetTransformInfo *TTI;
|
|
};
|
|
} // End of anonymous namespace
|
|
|
|
// Register this pass.
|
|
char CostModelAnalysis::ID = 0;
|
|
static const char cm_name[] = "Cost Model Analysis";
|
|
INITIALIZE_PASS_BEGIN(CostModelAnalysis, CM_NAME, cm_name, false, true)
|
|
INITIALIZE_PASS_END (CostModelAnalysis, CM_NAME, cm_name, false, true)
|
|
|
|
FunctionPass *llvm::createCostModelAnalysisPass() {
|
|
return new CostModelAnalysis();
|
|
}
|
|
|
|
void
|
|
CostModelAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AU.setPreservesAll();
|
|
}
|
|
|
|
bool
|
|
CostModelAnalysis::runOnFunction(Function &F) {
|
|
this->F = &F;
|
|
auto *TTIWP = getAnalysisIfAvailable<TargetTransformInfoWrapperPass>();
|
|
TTI = TTIWP ? &TTIWP->getTTI(F) : nullptr;
|
|
|
|
return false;
|
|
}
|
|
|
|
void CostModelAnalysis::print(raw_ostream &OS, const Module*) const {
|
|
if (!F)
|
|
return;
|
|
|
|
for (BasicBlock &B : *F) {
|
|
for (Instruction &Inst : B) {
|
|
InstructionCost Cost = TTI->getInstructionCost(&Inst, CostKind);
|
|
if (auto CostVal = Cost.getValue())
|
|
OS << "Cost Model: Found an estimated cost of " << *CostVal;
|
|
else
|
|
OS << "Cost Model: Invalid cost";
|
|
|
|
OS << " for instruction: " << Inst << "\n";
|
|
}
|
|
}
|
|
}
|