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llvm-project/llvm/lib/Target/AMDGPU/AMDGPUCodeGenPrepare.cpp

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//===-- AMDGPUCodeGenPrepare.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 does misc. AMDGPU optimizations on IR before instruction
/// selection.
//
//===----------------------------------------------------------------------===//
#include "AMDGPU.h"
#include "AMDGPUSubtarget.h"
#include "AMDGPUTargetMachine.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/LegacyDivergenceAnalysis.h"
#include "llvm/Analysis/Loads.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include <cassert>
#include <iterator>
#define DEBUG_TYPE "amdgpu-codegenprepare"
using namespace llvm;
namespace {
static cl::opt<bool> WidenLoads(
"amdgpu-codegenprepare-widen-constant-loads",
cl::desc("Widen sub-dword constant address space loads in AMDGPUCodeGenPrepare"),
cl::ReallyHidden,
cl::init(true));
class AMDGPUCodeGenPrepare : public FunctionPass,
public InstVisitor<AMDGPUCodeGenPrepare, bool> {
const GCNSubtarget *ST = nullptr;
AssumptionCache *AC = nullptr;
LegacyDivergenceAnalysis *DA = nullptr;
Module *Mod = nullptr;
bool HasUnsafeFPMath = false;
/// Copies exact/nsw/nuw flags (if any) from binary operation \p I to
/// binary operation \p V.
///
/// \returns Binary operation \p V.
/// \returns \p T's base element bit width.
unsigned getBaseElementBitWidth(const Type *T) const;
/// \returns Equivalent 32 bit integer type for given type \p T. For example,
/// if \p T is i7, then i32 is returned; if \p T is <3 x i12>, then <3 x i32>
/// is returned.
Type *getI32Ty(IRBuilder<> &B, const Type *T) const;
/// \returns True if binary operation \p I is a signed binary operation, false
/// otherwise.
bool isSigned(const BinaryOperator &I) const;
/// \returns True if the condition of 'select' operation \p I comes from a
/// signed 'icmp' operation, false otherwise.
bool isSigned(const SelectInst &I) const;
/// \returns True if type \p T needs to be promoted to 32 bit integer type,
/// false otherwise.
bool needsPromotionToI32(const Type *T) const;
/// Promotes uniform binary operation \p I to equivalent 32 bit binary
/// operation.
///
/// \details \p I's base element bit width must be greater than 1 and less
/// than or equal 16. Promotion is done by sign or zero extending operands to
/// 32 bits, replacing \p I with equivalent 32 bit binary operation, and
/// truncating the result of 32 bit binary operation back to \p I's original
/// type. Division operation is not promoted.
///
/// \returns True if \p I is promoted to equivalent 32 bit binary operation,
/// false otherwise.
bool promoteUniformOpToI32(BinaryOperator &I) const;
/// Promotes uniform 'icmp' operation \p I to 32 bit 'icmp' operation.
///
/// \details \p I's base element bit width must be greater than 1 and less
/// than or equal 16. Promotion is done by sign or zero extending operands to
/// 32 bits, and replacing \p I with 32 bit 'icmp' operation.
///
/// \returns True.
bool promoteUniformOpToI32(ICmpInst &I) const;
/// Promotes uniform 'select' operation \p I to 32 bit 'select'
/// operation.
///
/// \details \p I's base element bit width must be greater than 1 and less
/// than or equal 16. Promotion is done by sign or zero extending operands to
/// 32 bits, replacing \p I with 32 bit 'select' operation, and truncating the
/// result of 32 bit 'select' operation back to \p I's original type.
///
/// \returns True.
bool promoteUniformOpToI32(SelectInst &I) const;
/// Promotes uniform 'bitreverse' intrinsic \p I to 32 bit 'bitreverse'
/// intrinsic.
///
/// \details \p I's base element bit width must be greater than 1 and less
/// than or equal 16. Promotion is done by zero extending the operand to 32
/// bits, replacing \p I with 32 bit 'bitreverse' intrinsic, shifting the
/// result of 32 bit 'bitreverse' intrinsic to the right with zero fill (the
/// shift amount is 32 minus \p I's base element bit width), and truncating
/// the result of the shift operation back to \p I's original type.
///
/// \returns True.
bool promoteUniformBitreverseToI32(IntrinsicInst &I) const;
/// Expands 24 bit div or rem.
Value* expandDivRem24(IRBuilder<> &Builder, BinaryOperator &I,
Value *Num, Value *Den,
bool IsDiv, bool IsSigned) const;
/// Expands 32 bit div or rem.
Value* expandDivRem32(IRBuilder<> &Builder, BinaryOperator &I,
Value *Num, Value *Den) const;
/// Widen a scalar load.
///
/// \details \p Widen scalar load for uniform, small type loads from constant
// memory / to a full 32-bits and then truncate the input to allow a scalar
// load instead of a vector load.
//
/// \returns True.
bool canWidenScalarExtLoad(LoadInst &I) const;
public:
static char ID;
AMDGPUCodeGenPrepare() : FunctionPass(ID) {}
bool visitFDiv(BinaryOperator &I);
bool visitInstruction(Instruction &I) { return false; }
bool visitBinaryOperator(BinaryOperator &I);
bool visitLoadInst(LoadInst &I);
bool visitICmpInst(ICmpInst &I);
bool visitSelectInst(SelectInst &I);
bool visitIntrinsicInst(IntrinsicInst &I);
bool visitBitreverseIntrinsicInst(IntrinsicInst &I);
bool doInitialization(Module &M) override;
bool runOnFunction(Function &F) override;
StringRef getPassName() const override { return "AMDGPU IR optimizations"; }
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AssumptionCacheTracker>();
AU.addRequired<LegacyDivergenceAnalysis>();
AU.setPreservesAll();
}
};
} // end anonymous namespace
unsigned AMDGPUCodeGenPrepare::getBaseElementBitWidth(const Type *T) const {
assert(needsPromotionToI32(T) && "T does not need promotion to i32");
if (T->isIntegerTy())
return T->getIntegerBitWidth();
return cast<VectorType>(T)->getElementType()->getIntegerBitWidth();
}
Type *AMDGPUCodeGenPrepare::getI32Ty(IRBuilder<> &B, const Type *T) const {
assert(needsPromotionToI32(T) && "T does not need promotion to i32");
if (T->isIntegerTy())
return B.getInt32Ty();
return VectorType::get(B.getInt32Ty(), cast<VectorType>(T)->getNumElements());
}
bool AMDGPUCodeGenPrepare::isSigned(const BinaryOperator &I) const {
return I.getOpcode() == Instruction::AShr ||
I.getOpcode() == Instruction::SDiv || I.getOpcode() == Instruction::SRem;
}
bool AMDGPUCodeGenPrepare::isSigned(const SelectInst &I) const {
return isa<ICmpInst>(I.getOperand(0)) ?
cast<ICmpInst>(I.getOperand(0))->isSigned() : false;
}
bool AMDGPUCodeGenPrepare::needsPromotionToI32(const Type *T) const {
const IntegerType *IntTy = dyn_cast<IntegerType>(T);
if (IntTy && IntTy->getBitWidth() > 1 && IntTy->getBitWidth() <= 16)
return true;
if (const VectorType *VT = dyn_cast<VectorType>(T)) {
// TODO: The set of packed operations is more limited, so may want to
// promote some anyway.
if (ST->hasVOP3PInsts())
return false;
return needsPromotionToI32(VT->getElementType());
}
return false;
}
// Return true if the op promoted to i32 should have nsw set.
static bool promotedOpIsNSW(const Instruction &I) {
switch (I.getOpcode()) {
case Instruction::Shl:
case Instruction::Add:
case Instruction::Sub:
return true;
case Instruction::Mul:
return I.hasNoUnsignedWrap();
default:
return false;
}
}
// Return true if the op promoted to i32 should have nuw set.
static bool promotedOpIsNUW(const Instruction &I) {
switch (I.getOpcode()) {
case Instruction::Shl:
case Instruction::Add:
case Instruction::Mul:
return true;
case Instruction::Sub:
return I.hasNoUnsignedWrap();
default:
return false;
}
}
bool AMDGPUCodeGenPrepare::canWidenScalarExtLoad(LoadInst &I) const {
Type *Ty = I.getType();
const DataLayout &DL = Mod->getDataLayout();
int TySize = DL.getTypeSizeInBits(Ty);
unsigned Align = I.getAlignment() ?
I.getAlignment() : DL.getABITypeAlignment(Ty);
return I.isSimple() && TySize < 32 && Align >= 4 && DA->isUniform(&I);
}
bool AMDGPUCodeGenPrepare::promoteUniformOpToI32(BinaryOperator &I) const {
assert(needsPromotionToI32(I.getType()) &&
"I does not need promotion to i32");
if (I.getOpcode() == Instruction::SDiv ||
I.getOpcode() == Instruction::UDiv ||
I.getOpcode() == Instruction::SRem ||
I.getOpcode() == Instruction::URem)
return false;
IRBuilder<> Builder(&I);
Builder.SetCurrentDebugLocation(I.getDebugLoc());
Type *I32Ty = getI32Ty(Builder, I.getType());
Value *ExtOp0 = nullptr;
Value *ExtOp1 = nullptr;
Value *ExtRes = nullptr;
Value *TruncRes = nullptr;
if (isSigned(I)) {
ExtOp0 = Builder.CreateSExt(I.getOperand(0), I32Ty);
ExtOp1 = Builder.CreateSExt(I.getOperand(1), I32Ty);
} else {
ExtOp0 = Builder.CreateZExt(I.getOperand(0), I32Ty);
ExtOp1 = Builder.CreateZExt(I.getOperand(1), I32Ty);
}
ExtRes = Builder.CreateBinOp(I.getOpcode(), ExtOp0, ExtOp1);
if (Instruction *Inst = dyn_cast<Instruction>(ExtRes)) {
if (promotedOpIsNSW(cast<Instruction>(I)))
Inst->setHasNoSignedWrap();
if (promotedOpIsNUW(cast<Instruction>(I)))
Inst->setHasNoUnsignedWrap();
if (const auto *ExactOp = dyn_cast<PossiblyExactOperator>(&I))
Inst->setIsExact(ExactOp->isExact());
}
TruncRes = Builder.CreateTrunc(ExtRes, I.getType());
I.replaceAllUsesWith(TruncRes);
I.eraseFromParent();
return true;
}
bool AMDGPUCodeGenPrepare::promoteUniformOpToI32(ICmpInst &I) const {
assert(needsPromotionToI32(I.getOperand(0)->getType()) &&
"I does not need promotion to i32");
IRBuilder<> Builder(&I);
Builder.SetCurrentDebugLocation(I.getDebugLoc());
Type *I32Ty = getI32Ty(Builder, I.getOperand(0)->getType());
Value *ExtOp0 = nullptr;
Value *ExtOp1 = nullptr;
Value *NewICmp = nullptr;
if (I.isSigned()) {
ExtOp0 = Builder.CreateSExt(I.getOperand(0), I32Ty);
ExtOp1 = Builder.CreateSExt(I.getOperand(1), I32Ty);
} else {
ExtOp0 = Builder.CreateZExt(I.getOperand(0), I32Ty);
ExtOp1 = Builder.CreateZExt(I.getOperand(1), I32Ty);
}
NewICmp = Builder.CreateICmp(I.getPredicate(), ExtOp0, ExtOp1);
I.replaceAllUsesWith(NewICmp);
I.eraseFromParent();
return true;
}
bool AMDGPUCodeGenPrepare::promoteUniformOpToI32(SelectInst &I) const {
assert(needsPromotionToI32(I.getType()) &&
"I does not need promotion to i32");
IRBuilder<> Builder(&I);
Builder.SetCurrentDebugLocation(I.getDebugLoc());
Type *I32Ty = getI32Ty(Builder, I.getType());
Value *ExtOp1 = nullptr;
Value *ExtOp2 = nullptr;
Value *ExtRes = nullptr;
Value *TruncRes = nullptr;
if (isSigned(I)) {
ExtOp1 = Builder.CreateSExt(I.getOperand(1), I32Ty);
ExtOp2 = Builder.CreateSExt(I.getOperand(2), I32Ty);
} else {
ExtOp1 = Builder.CreateZExt(I.getOperand(1), I32Ty);
ExtOp2 = Builder.CreateZExt(I.getOperand(2), I32Ty);
}
ExtRes = Builder.CreateSelect(I.getOperand(0), ExtOp1, ExtOp2);
TruncRes = Builder.CreateTrunc(ExtRes, I.getType());
I.replaceAllUsesWith(TruncRes);
I.eraseFromParent();
return true;
}
bool AMDGPUCodeGenPrepare::promoteUniformBitreverseToI32(
IntrinsicInst &I) const {
assert(I.getIntrinsicID() == Intrinsic::bitreverse &&
"I must be bitreverse intrinsic");
assert(needsPromotionToI32(I.getType()) &&
"I does not need promotion to i32");
IRBuilder<> Builder(&I);
Builder.SetCurrentDebugLocation(I.getDebugLoc());
Type *I32Ty = getI32Ty(Builder, I.getType());
Function *I32 =
Intrinsic::getDeclaration(Mod, Intrinsic::bitreverse, { I32Ty });
Value *ExtOp = Builder.CreateZExt(I.getOperand(0), I32Ty);
Value *ExtRes = Builder.CreateCall(I32, { ExtOp });
Value *LShrOp =
Builder.CreateLShr(ExtRes, 32 - getBaseElementBitWidth(I.getType()));
Value *TruncRes =
Builder.CreateTrunc(LShrOp, I.getType());
I.replaceAllUsesWith(TruncRes);
I.eraseFromParent();
return true;
}
static bool shouldKeepFDivF32(Value *Num, bool UnsafeDiv, bool HasDenormals) {
const ConstantFP *CNum = dyn_cast<ConstantFP>(Num);
if (!CNum)
return HasDenormals;
if (UnsafeDiv)
return true;
bool IsOne = CNum->isExactlyValue(+1.0) || CNum->isExactlyValue(-1.0);
// Reciprocal f32 is handled separately without denormals.
return HasDenormals ^ IsOne;
}
// Insert an intrinsic for fast fdiv for safe math situations where we can
// reduce precision. Leave fdiv for situations where the generic node is
// expected to be optimized.
bool AMDGPUCodeGenPrepare::visitFDiv(BinaryOperator &FDiv) {
Type *Ty = FDiv.getType();
if (!Ty->getScalarType()->isFloatTy())
return false;
MDNode *FPMath = FDiv.getMetadata(LLVMContext::MD_fpmath);
if (!FPMath)
return false;
const FPMathOperator *FPOp = cast<const FPMathOperator>(&FDiv);
float ULP = FPOp->getFPAccuracy();
if (ULP < 2.5f)
return false;
FastMathFlags FMF = FPOp->getFastMathFlags();
bool UnsafeDiv = HasUnsafeFPMath || FMF.isFast() ||
FMF.allowReciprocal();
// With UnsafeDiv node will be optimized to just rcp and mul.
if (UnsafeDiv)
return false;
IRBuilder<> Builder(FDiv.getParent(), std::next(FDiv.getIterator()), FPMath);
Builder.setFastMathFlags(FMF);
Builder.SetCurrentDebugLocation(FDiv.getDebugLoc());
Function *Decl = Intrinsic::getDeclaration(Mod, Intrinsic::amdgcn_fdiv_fast);
Value *Num = FDiv.getOperand(0);
Value *Den = FDiv.getOperand(1);
Value *NewFDiv = nullptr;
bool HasDenormals = ST->hasFP32Denormals();
if (VectorType *VT = dyn_cast<VectorType>(Ty)) {
NewFDiv = UndefValue::get(VT);
// FIXME: Doesn't do the right thing for cases where the vector is partially
// constant. This works when the scalarizer pass is run first.
for (unsigned I = 0, E = VT->getNumElements(); I != E; ++I) {
Value *NumEltI = Builder.CreateExtractElement(Num, I);
Value *DenEltI = Builder.CreateExtractElement(Den, I);
Value *NewElt;
if (shouldKeepFDivF32(NumEltI, UnsafeDiv, HasDenormals)) {
NewElt = Builder.CreateFDiv(NumEltI, DenEltI);
} else {
NewElt = Builder.CreateCall(Decl, { NumEltI, DenEltI });
}
NewFDiv = Builder.CreateInsertElement(NewFDiv, NewElt, I);
}
} else {
if (!shouldKeepFDivF32(Num, UnsafeDiv, HasDenormals))
NewFDiv = Builder.CreateCall(Decl, { Num, Den });
}
if (NewFDiv) {
FDiv.replaceAllUsesWith(NewFDiv);
NewFDiv->takeName(&FDiv);
FDiv.eraseFromParent();
}
return !!NewFDiv;
}
static bool hasUnsafeFPMath(const Function &F) {
Attribute Attr = F.getFnAttribute("unsafe-fp-math");
return Attr.getValueAsString() == "true";
}
static std::pair<Value*, Value*> getMul64(IRBuilder<> &Builder,
Value *LHS, Value *RHS) {
Type *I32Ty = Builder.getInt32Ty();
Type *I64Ty = Builder.getInt64Ty();
Value *LHS_EXT64 = Builder.CreateZExt(LHS, I64Ty);
Value *RHS_EXT64 = Builder.CreateZExt(RHS, I64Ty);
Value *MUL64 = Builder.CreateMul(LHS_EXT64, RHS_EXT64);
Value *Lo = Builder.CreateTrunc(MUL64, I32Ty);
Value *Hi = Builder.CreateLShr(MUL64, Builder.getInt64(32));
Hi = Builder.CreateTrunc(Hi, I32Ty);
return std::make_pair(Lo, Hi);
}
static Value* getMulHu(IRBuilder<> &Builder, Value *LHS, Value *RHS) {
return getMul64(Builder, LHS, RHS).second;
}
// The fractional part of a float is enough to accurately represent up to
// a 24-bit signed integer.
Value* AMDGPUCodeGenPrepare::expandDivRem24(IRBuilder<> &Builder,
BinaryOperator &I,
Value *Num, Value *Den,
bool IsDiv, bool IsSigned) const {
assert(Num->getType()->isIntegerTy(32));
const DataLayout &DL = Mod->getDataLayout();
unsigned LHSSignBits = ComputeNumSignBits(Num, DL, 0, AC, &I);
if (LHSSignBits < 9)
return nullptr;
unsigned RHSSignBits = ComputeNumSignBits(Den, DL, 0, AC, &I);
if (RHSSignBits < 9)
return nullptr;
unsigned SignBits = std::min(LHSSignBits, RHSSignBits);
unsigned DivBits = 32 - SignBits;
if (IsSigned)
++DivBits;
Type *Ty = Num->getType();
Type *I32Ty = Builder.getInt32Ty();
Type *F32Ty = Builder.getFloatTy();
ConstantInt *One = Builder.getInt32(1);
Value *JQ = One;
if (IsSigned) {
// char|short jq = ia ^ ib;
JQ = Builder.CreateXor(Num, Den);
// jq = jq >> (bitsize - 2)
JQ = Builder.CreateAShr(JQ, Builder.getInt32(30));
// jq = jq | 0x1
JQ = Builder.CreateOr(JQ, One);
}
// int ia = (int)LHS;
Value *IA = Num;
// int ib, (int)RHS;
Value *IB = Den;
// float fa = (float)ia;
Value *FA = IsSigned ? Builder.CreateSIToFP(IA, F32Ty)
: Builder.CreateUIToFP(IA, F32Ty);
// float fb = (float)ib;
Value *FB = IsSigned ? Builder.CreateSIToFP(IB,F32Ty)
: Builder.CreateUIToFP(IB,F32Ty);
Value *RCP = Builder.CreateFDiv(ConstantFP::get(F32Ty, 1.0), FB);
Value *FQM = Builder.CreateFMul(FA, RCP);
// fq = trunc(fqm);
CallInst *FQ = Builder.CreateUnaryIntrinsic(Intrinsic::trunc, FQM);
FQ->copyFastMathFlags(Builder.getFastMathFlags());
// float fqneg = -fq;
Value *FQNeg = Builder.CreateFNeg(FQ);
// float fr = mad(fqneg, fb, fa);
Value *FR = Builder.CreateIntrinsic(Intrinsic::amdgcn_fmad_ftz,
{FQNeg->getType()}, {FQNeg, FB, FA}, FQ);
// int iq = (int)fq;
Value *IQ = IsSigned ? Builder.CreateFPToSI(FQ, I32Ty)
: Builder.CreateFPToUI(FQ, I32Ty);
// fr = fabs(fr);
FR = Builder.CreateUnaryIntrinsic(Intrinsic::fabs, FR, FQ);
// fb = fabs(fb);
FB = Builder.CreateUnaryIntrinsic(Intrinsic::fabs, FB, FQ);
// int cv = fr >= fb;
Value *CV = Builder.CreateFCmpOGE(FR, FB);
// jq = (cv ? jq : 0);
JQ = Builder.CreateSelect(CV, JQ, Builder.getInt32(0));
// dst = iq + jq;
Value *Div = Builder.CreateAdd(IQ, JQ);
Value *Res = Div;
if (!IsDiv) {
// Rem needs compensation, it's easier to recompute it
Value *Rem = Builder.CreateMul(Div, Den);
Res = Builder.CreateSub(Num, Rem);
}
// Truncate to number of bits this divide really is.
if (IsSigned) {
Res = Builder.CreateTrunc(Res, Builder.getIntNTy(DivBits));
Res = Builder.CreateSExt(Res, Ty);
} else {
ConstantInt *TruncMask = Builder.getInt32((UINT64_C(1) << DivBits) - 1);
Res = Builder.CreateAnd(Res, TruncMask);
}
return Res;
}
Value* AMDGPUCodeGenPrepare::expandDivRem32(IRBuilder<> &Builder,
BinaryOperator &I,
Value *Num, Value *Den) const {
Instruction::BinaryOps Opc = I.getOpcode();
assert(Opc == Instruction::URem || Opc == Instruction::UDiv ||
Opc == Instruction::SRem || Opc == Instruction::SDiv);
FastMathFlags FMF;
FMF.setFast();
Builder.setFastMathFlags(FMF);
if (isa<Constant>(Den))
return nullptr; // Keep it for optimization
bool IsDiv = Opc == Instruction::UDiv || Opc == Instruction::SDiv;
bool IsSigned = Opc == Instruction::SRem || Opc == Instruction::SDiv;
Type *Ty = Num->getType();
Type *I32Ty = Builder.getInt32Ty();
Type *F32Ty = Builder.getFloatTy();
if (Ty->getScalarSizeInBits() < 32) {
if (IsSigned) {
Num = Builder.CreateSExt(Num, I32Ty);
Den = Builder.CreateSExt(Den, I32Ty);
} else {
Num = Builder.CreateZExt(Num, I32Ty);
Den = Builder.CreateZExt(Den, I32Ty);
}
}
if (Value *Res = expandDivRem24(Builder, I, Num, Den, IsDiv, IsSigned)) {
Res = Builder.CreateTrunc(Res, Ty);
return Res;
}
ConstantInt *Zero = Builder.getInt32(0);
ConstantInt *One = Builder.getInt32(1);
ConstantInt *MinusOne = Builder.getInt32(~0);
Value *Sign = nullptr;
if (IsSigned) {
ConstantInt *K31 = Builder.getInt32(31);
Value *LHSign = Builder.CreateAShr(Num, K31);
Value *RHSign = Builder.CreateAShr(Den, K31);
// Remainder sign is the same as LHS
Sign = IsDiv ? Builder.CreateXor(LHSign, RHSign) : LHSign;
Num = Builder.CreateAdd(Num, LHSign);
Den = Builder.CreateAdd(Den, RHSign);
Num = Builder.CreateXor(Num, LHSign);
Den = Builder.CreateXor(Den, RHSign);
}
// RCP = URECIP(Den) = 2^32 / Den + e
// e is rounding error.
Value *DEN_F32 = Builder.CreateUIToFP(Den, F32Ty);
Value *RCP_F32 = Builder.CreateFDiv(ConstantFP::get(F32Ty, 1.0), DEN_F32);
Constant *UINT_MAX_PLUS_1 = ConstantFP::get(F32Ty, BitsToFloat(0x4f800000));
Value *RCP_SCALE = Builder.CreateFMul(RCP_F32, UINT_MAX_PLUS_1);
Value *RCP = Builder.CreateFPToUI(RCP_SCALE, I32Ty);
// RCP_LO, RCP_HI = mul(RCP, Den) */
Value *RCP_LO, *RCP_HI;
std::tie(RCP_LO, RCP_HI) = getMul64(Builder, RCP, Den);
// NEG_RCP_LO = -RCP_LO
Value *NEG_RCP_LO = Builder.CreateNeg(RCP_LO);
// ABS_RCP_LO = (RCP_HI == 0 ? NEG_RCP_LO : RCP_LO)
Value *RCP_HI_0_CC = Builder.CreateICmpEQ(RCP_HI, Zero);
Value *ABS_RCP_LO = Builder.CreateSelect(RCP_HI_0_CC, NEG_RCP_LO, RCP_LO);
// Calculate the rounding error from the URECIP instruction
// E = mulhu(ABS_RCP_LO, RCP)
Value *E = getMulHu(Builder, ABS_RCP_LO, RCP);
// RCP_A_E = RCP + E
Value *RCP_A_E = Builder.CreateAdd(RCP, E);
// RCP_S_E = RCP - E
Value *RCP_S_E = Builder.CreateSub(RCP, E);
// Tmp0 = (RCP_HI == 0 ? RCP_A_E : RCP_SUB_E)
Value *Tmp0 = Builder.CreateSelect(RCP_HI_0_CC, RCP_A_E, RCP_S_E);
// Quotient = mulhu(Tmp0, Num)
Value *Quotient = getMulHu(Builder, Tmp0, Num);
// Num_S_Remainder = Quotient * Den
Value *Num_S_Remainder = Builder.CreateMul(Quotient, Den);
// Remainder = Num - Num_S_Remainder
Value *Remainder = Builder.CreateSub(Num, Num_S_Remainder);
// Remainder_GE_Den = (Remainder >= Den ? -1 : 0)
Value *Rem_GE_Den_CC = Builder.CreateICmpUGE(Remainder, Den);
Value *Remainder_GE_Den = Builder.CreateSelect(Rem_GE_Den_CC, MinusOne, Zero);
// Remainder_GE_Zero = (Num >= Num_S_Remainder ? -1 : 0)
Value *Num_GE_Num_S_Rem_CC = Builder.CreateICmpUGE(Num, Num_S_Remainder);
Value *Remainder_GE_Zero = Builder.CreateSelect(Num_GE_Num_S_Rem_CC,
MinusOne, Zero);
// Tmp1 = Remainder_GE_Den & Remainder_GE_Zero
Value *Tmp1 = Builder.CreateAnd(Remainder_GE_Den, Remainder_GE_Zero);
Value *Tmp1_0_CC = Builder.CreateICmpEQ(Tmp1, Zero);
Value *Res;
if (IsDiv) {
// Quotient_A_One = Quotient + 1
Value *Quotient_A_One = Builder.CreateAdd(Quotient, One);
// Quotient_S_One = Quotient - 1
Value *Quotient_S_One = Builder.CreateSub(Quotient, One);
// Div = (Tmp1 == 0 ? Quotient : Quotient_A_One)
Value *Div = Builder.CreateSelect(Tmp1_0_CC, Quotient, Quotient_A_One);
// Div = (Remainder_GE_Zero == 0 ? Quotient_S_One : Div)
Res = Builder.CreateSelect(Num_GE_Num_S_Rem_CC, Div, Quotient_S_One);
} else {
// Remainder_S_Den = Remainder - Den
Value *Remainder_S_Den = Builder.CreateSub(Remainder, Den);
// Remainder_A_Den = Remainder + Den
Value *Remainder_A_Den = Builder.CreateAdd(Remainder, Den);
// Rem = (Tmp1 == 0 ? Remainder : Remainder_S_Den)
Value *Rem = Builder.CreateSelect(Tmp1_0_CC, Remainder, Remainder_S_Den);
// Rem = (Remainder_GE_Zero == 0 ? Remainder_A_Den : Rem)
Res = Builder.CreateSelect(Num_GE_Num_S_Rem_CC, Rem, Remainder_A_Den);
}
if (IsSigned) {
Res = Builder.CreateXor(Res, Sign);
Res = Builder.CreateSub(Res, Sign);
}
Res = Builder.CreateTrunc(Res, Ty);
return Res;
}
bool AMDGPUCodeGenPrepare::visitBinaryOperator(BinaryOperator &I) {
if (ST->has16BitInsts() && needsPromotionToI32(I.getType()) &&
DA->isUniform(&I) && promoteUniformOpToI32(I))
return true;
bool Changed = false;
Instruction::BinaryOps Opc = I.getOpcode();
Type *Ty = I.getType();
Value *NewDiv = nullptr;
if ((Opc == Instruction::URem || Opc == Instruction::UDiv ||
Opc == Instruction::SRem || Opc == Instruction::SDiv) &&
Ty->getScalarSizeInBits() <= 32) {
Value *Num = I.getOperand(0);
Value *Den = I.getOperand(1);
IRBuilder<> Builder(&I);
Builder.SetCurrentDebugLocation(I.getDebugLoc());
if (VectorType *VT = dyn_cast<VectorType>(Ty)) {
NewDiv = UndefValue::get(VT);
for (unsigned N = 0, E = VT->getNumElements(); N != E; ++N) {
Value *NumEltN = Builder.CreateExtractElement(Num, N);
Value *DenEltN = Builder.CreateExtractElement(Den, N);
Value *NewElt = expandDivRem32(Builder, I, NumEltN, DenEltN);
if (!NewElt)
NewElt = Builder.CreateBinOp(Opc, NumEltN, DenEltN);
NewDiv = Builder.CreateInsertElement(NewDiv, NewElt, N);
}
} else {
NewDiv = expandDivRem32(Builder, I, Num, Den);
}
if (NewDiv) {
I.replaceAllUsesWith(NewDiv);
I.eraseFromParent();
Changed = true;
}
}
return Changed;
}
bool AMDGPUCodeGenPrepare::visitLoadInst(LoadInst &I) {
if (!WidenLoads)
return false;
if ((I.getPointerAddressSpace() == AMDGPUAS::CONSTANT_ADDRESS ||
I.getPointerAddressSpace() == AMDGPUAS::CONSTANT_ADDRESS_32BIT) &&
canWidenScalarExtLoad(I)) {
IRBuilder<> Builder(&I);
Builder.SetCurrentDebugLocation(I.getDebugLoc());
Type *I32Ty = Builder.getInt32Ty();
Type *PT = PointerType::get(I32Ty, I.getPointerAddressSpace());
Value *BitCast= Builder.CreateBitCast(I.getPointerOperand(), PT);
LoadInst *WidenLoad = Builder.CreateLoad(I32Ty, BitCast);
WidenLoad->copyMetadata(I);
// If we have range metadata, we need to convert the type, and not make
// assumptions about the high bits.
if (auto *Range = WidenLoad->getMetadata(LLVMContext::MD_range)) {
ConstantInt *Lower =
mdconst::extract<ConstantInt>(Range->getOperand(0));
if (Lower->getValue().isNullValue()) {
WidenLoad->setMetadata(LLVMContext::MD_range, nullptr);
} else {
Metadata *LowAndHigh[] = {
ConstantAsMetadata::get(ConstantInt::get(I32Ty, Lower->getValue().zext(32))),
// Don't make assumptions about the high bits.
ConstantAsMetadata::get(ConstantInt::get(I32Ty, 0))
};
WidenLoad->setMetadata(LLVMContext::MD_range,
MDNode::get(Mod->getContext(), LowAndHigh));
}
}
int TySize = Mod->getDataLayout().getTypeSizeInBits(I.getType());
Type *IntNTy = Builder.getIntNTy(TySize);
Value *ValTrunc = Builder.CreateTrunc(WidenLoad, IntNTy);
Value *ValOrig = Builder.CreateBitCast(ValTrunc, I.getType());
I.replaceAllUsesWith(ValOrig);
I.eraseFromParent();
return true;
}
return false;
}
bool AMDGPUCodeGenPrepare::visitICmpInst(ICmpInst &I) {
bool Changed = false;
if (ST->has16BitInsts() && needsPromotionToI32(I.getOperand(0)->getType()) &&
DA->isUniform(&I))
Changed |= promoteUniformOpToI32(I);
return Changed;
}
bool AMDGPUCodeGenPrepare::visitSelectInst(SelectInst &I) {
bool Changed = false;
if (ST->has16BitInsts() && needsPromotionToI32(I.getType()) &&
DA->isUniform(&I))
Changed |= promoteUniformOpToI32(I);
return Changed;
}
bool AMDGPUCodeGenPrepare::visitIntrinsicInst(IntrinsicInst &I) {
switch (I.getIntrinsicID()) {
case Intrinsic::bitreverse:
return visitBitreverseIntrinsicInst(I);
default:
return false;
}
}
bool AMDGPUCodeGenPrepare::visitBitreverseIntrinsicInst(IntrinsicInst &I) {
bool Changed = false;
if (ST->has16BitInsts() && needsPromotionToI32(I.getType()) &&
DA->isUniform(&I))
Changed |= promoteUniformBitreverseToI32(I);
return Changed;
}
bool AMDGPUCodeGenPrepare::doInitialization(Module &M) {
Mod = &M;
return false;
}
bool AMDGPUCodeGenPrepare::runOnFunction(Function &F) {
if (skipFunction(F))
return false;
auto *TPC = getAnalysisIfAvailable<TargetPassConfig>();
if (!TPC)
return false;
const AMDGPUTargetMachine &TM = TPC->getTM<AMDGPUTargetMachine>();
ST = &TM.getSubtarget<GCNSubtarget>(F);
AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
DA = &getAnalysis<LegacyDivergenceAnalysis>();
HasUnsafeFPMath = hasUnsafeFPMath(F);
bool MadeChange = false;
for (BasicBlock &BB : F) {
BasicBlock::iterator Next;
for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; I = Next) {
Next = std::next(I);
MadeChange |= visit(*I);
}
}
return MadeChange;
}
INITIALIZE_PASS_BEGIN(AMDGPUCodeGenPrepare, DEBUG_TYPE,
"AMDGPU IR optimizations", false, false)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(LegacyDivergenceAnalysis)
INITIALIZE_PASS_END(AMDGPUCodeGenPrepare, DEBUG_TYPE, "AMDGPU IR optimizations",
false, false)
char AMDGPUCodeGenPrepare::ID = 0;
FunctionPass *llvm::createAMDGPUCodeGenPreparePass() {
return new AMDGPUCodeGenPrepare();
}
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