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https://github.com/c64scene-ar/llvm-6502.git
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01df2fa3c4
Implement the getUnrollingPreferences() function for AMDGPUTargetTransformInfo so that loops that do address calculations on pointers derived from alloca are unconditionally unrolled. Unrolling these loops makes it more likely that SROA will be able to eliminate the allocas, which is a big win for R600 since memory allocated by alloca (private memory) is really slow. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199916 91177308-0d34-0410-b5e6-96231b3b80d8
120 lines
4.2 KiB
C++
120 lines
4.2 KiB
C++
//===-- AMDGPUTargetTransformInfo.cpp - AMDGPU specific TTI pass ---------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// \file
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// This file implements a TargetTransformInfo analysis pass specific to the
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// AMDGPU target machine. It uses the target's detailed information to provide
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// more precise answers to certain TTI queries, while letting the target
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// independent and default TTI implementations handle the rest.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "AMDGPUtti"
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#include "AMDGPU.h"
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#include "AMDGPUTargetMachine.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/TargetTransformInfo.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Target/CostTable.h"
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#include "llvm/Target/TargetLowering.h"
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using namespace llvm;
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// Declare the pass initialization routine locally as target-specific passes
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// don't have a target-wide initialization entry point, and so we rely on the
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// pass constructor initialization.
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namespace llvm {
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void initializeAMDGPUTTIPass(PassRegistry &);
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}
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namespace {
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class AMDGPUTTI : public ImmutablePass, public TargetTransformInfo {
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const AMDGPUTargetMachine *TM;
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const AMDGPUSubtarget *ST;
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const AMDGPUTargetLowering *TLI;
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/// Estimate the overhead of scalarizing an instruction. Insert and Extract
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/// are set if the result needs to be inserted and/or extracted from vectors.
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unsigned getScalarizationOverhead(Type *Ty, bool Insert, bool Extract) const;
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public:
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AMDGPUTTI() : ImmutablePass(ID), TM(0), ST(0), TLI(0) {
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llvm_unreachable("This pass cannot be directly constructed");
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}
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AMDGPUTTI(const AMDGPUTargetMachine *TM)
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: ImmutablePass(ID), TM(TM), ST(TM->getSubtargetImpl()),
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TLI(TM->getTargetLowering()) {
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initializeAMDGPUTTIPass(*PassRegistry::getPassRegistry());
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}
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virtual void initializePass() { pushTTIStack(this); }
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virtual void finalizePass() { popTTIStack(); }
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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TargetTransformInfo::getAnalysisUsage(AU);
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}
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/// Pass identification.
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static char ID;
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/// Provide necessary pointer adjustments for the two base classes.
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virtual void *getAdjustedAnalysisPointer(const void *ID) {
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if (ID == &TargetTransformInfo::ID)
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return (TargetTransformInfo *)this;
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return this;
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}
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virtual bool hasBranchDivergence() const;
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virtual void getUnrollingPreferences(Loop *L, UnrollingPreferences &UP) const;
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/// @}
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};
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} // end anonymous namespace
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INITIALIZE_AG_PASS(AMDGPUTTI, TargetTransformInfo, "AMDGPUtti",
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"AMDGPU Target Transform Info", true, true, false)
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char AMDGPUTTI::ID = 0;
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ImmutablePass *
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llvm::createAMDGPUTargetTransformInfoPass(const AMDGPUTargetMachine *TM) {
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return new AMDGPUTTI(TM);
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}
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bool AMDGPUTTI::hasBranchDivergence() const { return true; }
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void AMDGPUTTI::getUnrollingPreferences(Loop *L,
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UnrollingPreferences &UP) const {
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for (Loop::block_iterator BI = L->block_begin(), BE = L->block_end();
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BI != BE; ++BI) {
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BasicBlock *BB = *BI;
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for (BasicBlock::const_iterator I = BB->begin(), E = BB->end();
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I != E; ++I) {
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const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I);
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if (!GEP)
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continue;
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const Value *Ptr = GEP->getPointerOperand();
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const AllocaInst *Alloca = dyn_cast<AllocaInst>(GetUnderlyingObject(Ptr));
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if (Alloca) {
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// We want to do whatever we can to limit the number of alloca
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// instructions that make it through to the code generator. allocas
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// require us to use indirect addressing, which is slow and prone to
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// compiler bugs. If this loop does an address calculation on an
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// alloca ptr, then we want to unconditionally unroll the loop. In most
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// cases, this will make it possible for SROA to eliminate these allocas.
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UP.Threshold = UINT_MAX;
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}
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}
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}
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}
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