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/*========================== begin_copyright_notice ============================
Copyright (C) 2019-2021 Intel Corporation
SPDX-License-Identifier: MIT
============================= end_copyright_notice ===========================*/
#include "Compiler/CodeGenPublic.h"
#include "Compiler/CISACodeGen/helper.h"
#include "Compiler/IGCPassSupport.h"
#include "common/IGCIRBuilder.h"
#include "LLVM3DBuilder/BuiltinsFrontend.hpp"
#include "UniformAssumptions.hpp"
#include "Probe/Assertion.h"
using namespace llvm;
namespace IGC {
char UniformAssumptions::ID = 0;
#define PASS_FLAG "UniformAssumptions"
#define PASS_DESCRIPTION "Detect non-uniform usage of textures and samplers and check if they may be assumed uniform."
#define PASS_CFG_ONLY false
#define PASS_ANALYSIS false
IGC_INITIALIZE_PASS_BEGIN(UniformAssumptions, PASS_FLAG, PASS_DESCRIPTION, PASS_CFG_ONLY, PASS_ANALYSIS)
IGC_INITIALIZE_PASS_DEPENDENCY(WIAnalysis)
IGC_INITIALIZE_PASS_DEPENDENCY(CodeGenContextWrapper)
IGC_INITIALIZE_PASS_END(UniformAssumptions, PASS_FLAG, PASS_DESCRIPTION, PASS_CFG_ONLY, PASS_ANALYSIS)
UniformAssumptions::UniformAssumptions() : llvm::FunctionPass(ID)
{
initializeUniformAssumptionsPass(*PassRegistry::getPassRegistry());
}
bool UniformAssumptions::runOnFunction(Function& F)
{
m_pCodeGenContext = getAnalysis<CodeGenContextWrapper>().getCodeGenContext();
m_WIAnalysis = &getAnalysis<WIAnalysis>();
if (m_WIAnalysis == nullptr || m_pCodeGenContext == nullptr)
{
IGC_ASSERT(0);
return false;
}
// Propagate assumptions backwards (if safe) to increase the coverage.
HoistAssumptions(F);
// Try optimizing non-uniform resource accesses to uniform (to prevent from adding ResourceLoops)
OptimizeResourceAccesses(F);
return m_changed;
}
void UniformAssumptions::visitCallInst(CallInst& CI)
{
if (m_collectingAssumptions)
{
if (llvm::GenIntrinsicInst * pIntr = llvm::dyn_cast<llvm::GenIntrinsicInst>(&CI))
{
if (pIntr->getIntrinsicID() == GenISAIntrinsic::GenISA_is_uniform)
{
m_assumptions.push_back(pIntr);
}
}
return;
}
if (llvm::GenIntrinsicInst * pIntr = llvm::dyn_cast<llvm::GenIntrinsicInst>(&CI))
{
// Figure out the intrinsic operands for texture & sampler
llvm::Value* pTextureValue = nullptr;
llvm::Value*pSamplerValue = nullptr;
IGC::getTextureAndSamplerOperands(
pIntr,
pTextureValue,
pSamplerValue);
if (pTextureValue && pTextureValue->getType()->isPointerTy() &&
!m_WIAnalysis->isUniform(pTextureValue))
{
// Check assumptions for texture:
if (IsAssumedUniform(pTextureValue))
{
MakeUniformResourceOperand(pTextureValue, &CI);
}
}
if (pSamplerValue && pSamplerValue->getType()->isPointerTy() &&
!m_WIAnalysis->isUniform(pSamplerValue))
{
// Check assumptions for sampler:
if (IsAssumedUniform(pSamplerValue))
{
MakeUniformResourceOperand(pSamplerValue, &CI);
}
}
}
}
void UniformAssumptions::OptimizeResourceAccesses(llvm::Function& F)
{
IGC_ASSERT(m_collectingAssumptions == false);
visit(F);
}
bool UniformAssumptions::IsAssumedUniform(llvm::Value* V, int recursionLevel) const
{
if (recursionLevel >= s_cMaxRecursion)
{
// Limit level of recursion.
return false;
}
// Check if marked as uniform by WIAnalysis:
if (m_WIAnalysis->isUniform(V))
{
return true;
}
// Check if value can be assumed uniform:
for (auto UI = V->use_begin(), UE = V->use_end(); UI != UE; ++UI)
{
if (llvm::GenIntrinsicInst * pIntr = llvm::dyn_cast<llvm::GenIntrinsicInst>(UI->getUser()))
{
if (pIntr->getIntrinsicID() == GenISAIntrinsic::GenISA_is_uniform)
{
return true;
}
}
}
// This is very conservative simplification of rules implemented in Uniform Analysis (WIANalysis pass).
// Uniform Analysis additionally tries to prove some instructions to be uniform even if they do not
// have all uniform operands. Here, we simply assume that:
// - CallInst, AllocaInst, VAArgInst and PHINode that were marked by UA as non-uniform remain non-uniform.
// - Other instructions marked by UA as non-uniform can only be assumed uniform if all of its operands can be assumed uniform.
// In the future, it would be better to reuse Uniform Analysis logic here - it would be more reliable
// and would also optimize more cases.
if (llvm::isa<llvm::CallInst>(V) ||
llvm::isa<llvm::AllocaInst>(V) ||
llvm::isa<llvm::VAArgInst>(V) ||
llvm::isa<llvm::PHINode>(V))
{
return false;
}
// Check if all operands are uniform:
if (auto inst = dyn_cast<Instruction>(V))
{
for (auto& op : inst->operands())
{
if (!IsAssumedUniform(op, recursionLevel + 1))
{
return false;
}
}
return true;
}
return false;
}
void UniformAssumptions::MakeUniformResourceOperand(llvm::Value* V, llvm::CallInst* CI)
{
// Add readFirstLane to make value uniform.
LLVM3DBuilder<> builder(*m_pCodeGenContext->getLLVMContext(), m_pCodeGenContext->platform.getPlatformInfo());
builder.SetInsertPoint(CI);
Value* uniformTexture = builder.readFirstLane(V);
for (unsigned i = 0; i < CI->getNumOperands(); i++)
{
if (CI->getOperand(i) == V)
{
CI->setOperand(i, uniformTexture);
}
}
m_changed = true;
}
void UniformAssumptions::CollectAssumptions(llvm::Function& F)
{
m_assumptions.clear();
m_collectingAssumptions = true;
visit(F);
m_collectingAssumptions = false;
}
void UniformAssumptions::HoistAssumptions(llvm::Function& F)
{
CollectAssumptions(F);
// Try to propagate assumptions up.
for (auto A : m_assumptions)
{
auto src = A->getOperand(0);
bool check_further = true;
while (check_further)
{
check_further = false;
if (auto castInst = dyn_cast<CastInst>(src))
{
// if ext(A) is uniform then A is uniform too.
if (castInst->getOpcode() == Instruction::ZExt ||
castInst->getOpcode() == Instruction::SExt)
{
Instruction* newAssumption = A->clone();
src = castInst->getOperand(0);
newAssumption->setOperand(0, src);
if (auto srcInst = dyn_cast<Instruction>(src))
{
if (isa<PHINode>(srcInst))
{
newAssumption->insertBefore(
srcInst->getParent()->getFirstNonPHI());
}
else
{
newAssumption->insertAfter(srcInst);
}
}
else
{
newAssumption->insertBefore(
F.getEntryBlock().getFirstNonPHI());
}
check_further = true;
}
}
}
}
}
} // namespace IGC
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