244 lines
8.5 KiB
C++
244 lines
8.5 KiB
C++
//===- AMDGPUEmitPrintf.cpp -----------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// Utility function to lower a printf call into a series of device
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// library calls on the AMDGPU target.
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//
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// WARNING: This file knows about certain library functions. It recognizes them
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// by name, and hardwires knowledge of their semantics.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/AMDGPUEmitPrintf.h"
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#include "llvm/ADT/SparseBitVector.h"
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#include "llvm/Analysis/ValueTracking.h"
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using namespace llvm;
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#define DEBUG_TYPE "amdgpu-emit-printf"
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static bool isCString(const Value *Arg) {
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auto Ty = Arg->getType();
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auto PtrTy = dyn_cast<PointerType>(Ty);
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if (!PtrTy)
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return false;
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auto IntTy = dyn_cast<IntegerType>(PtrTy->getElementType());
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if (!IntTy)
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return false;
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return IntTy->getBitWidth() == 8;
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}
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static Value *fitArgInto64Bits(IRBuilder<> &Builder, Value *Arg) {
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auto Int64Ty = Builder.getInt64Ty();
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auto Ty = Arg->getType();
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if (auto IntTy = dyn_cast<IntegerType>(Ty)) {
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switch (IntTy->getBitWidth()) {
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case 32:
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return Builder.CreateZExt(Arg, Int64Ty);
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case 64:
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return Arg;
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}
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}
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if (Ty->getTypeID() == Type::DoubleTyID) {
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return Builder.CreateBitCast(Arg, Int64Ty);
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}
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if (isa<PointerType>(Ty)) {
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return Builder.CreatePtrToInt(Arg, Int64Ty);
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}
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llvm_unreachable("unexpected type");
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}
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static Value *callPrintfBegin(IRBuilder<> &Builder, Value *Version) {
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auto Int64Ty = Builder.getInt64Ty();
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auto M = Builder.GetInsertBlock()->getModule();
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auto Fn = M->getOrInsertFunction("__ockl_printf_begin", Int64Ty, Int64Ty);
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return Builder.CreateCall(Fn, Version);
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}
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static Value *callAppendArgs(IRBuilder<> &Builder, Value *Desc, int NumArgs,
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Value *Arg0, Value *Arg1, Value *Arg2, Value *Arg3,
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Value *Arg4, Value *Arg5, Value *Arg6,
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bool IsLast) {
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auto Int64Ty = Builder.getInt64Ty();
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auto Int32Ty = Builder.getInt32Ty();
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auto M = Builder.GetInsertBlock()->getModule();
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auto Fn = M->getOrInsertFunction("__ockl_printf_append_args", Int64Ty,
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Int64Ty, Int32Ty, Int64Ty, Int64Ty, Int64Ty,
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Int64Ty, Int64Ty, Int64Ty, Int64Ty, Int32Ty);
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auto IsLastValue = Builder.getInt32(IsLast);
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auto NumArgsValue = Builder.getInt32(NumArgs);
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return Builder.CreateCall(Fn, {Desc, NumArgsValue, Arg0, Arg1, Arg2, Arg3,
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Arg4, Arg5, Arg6, IsLastValue});
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}
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static Value *appendArg(IRBuilder<> &Builder, Value *Desc, Value *Arg,
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bool IsLast) {
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auto Arg0 = fitArgInto64Bits(Builder, Arg);
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auto Zero = Builder.getInt64(0);
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return callAppendArgs(Builder, Desc, 1, Arg0, Zero, Zero, Zero, Zero, Zero,
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Zero, IsLast);
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}
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// The device library does not provide strlen, so we build our own loop
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// here. While we are at it, we also include the terminating null in the length.
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static Value *getStrlenWithNull(IRBuilder<> &Builder, Value *Str) {
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auto *Prev = Builder.GetInsertBlock();
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Module *M = Prev->getModule();
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auto CharZero = Builder.getInt8(0);
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auto One = Builder.getInt64(1);
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auto Zero = Builder.getInt64(0);
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auto Int64Ty = Builder.getInt64Ty();
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// The length is either zero for a null pointer, or the computed value for an
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// actual string. We need a join block for a phi that represents the final
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// value.
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//
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// Strictly speaking, the zero does not matter since
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// __ockl_printf_append_string_n ignores the length if the pointer is null.
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BasicBlock *Join = nullptr;
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if (Prev->getTerminator()) {
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Join = Prev->splitBasicBlock(Builder.GetInsertPoint(),
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"strlen.join");
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Prev->getTerminator()->eraseFromParent();
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} else {
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Join = BasicBlock::Create(M->getContext(), "strlen.join",
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Prev->getParent());
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}
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BasicBlock *While =
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BasicBlock::Create(M->getContext(), "strlen.while",
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Prev->getParent(), Join);
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BasicBlock *WhileDone = BasicBlock::Create(
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M->getContext(), "strlen.while.done",
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Prev->getParent(), Join);
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// Emit an early return for when the pointer is null.
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Builder.SetInsertPoint(Prev);
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auto CmpNull =
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Builder.CreateICmpEQ(Str, Constant::getNullValue(Str->getType()));
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BranchInst::Create(Join, While, CmpNull, Prev);
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// Entry to the while loop.
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Builder.SetInsertPoint(While);
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auto PtrPhi = Builder.CreatePHI(Str->getType(), 2);
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PtrPhi->addIncoming(Str, Prev);
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auto PtrNext = Builder.CreateGEP(PtrPhi, One);
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PtrPhi->addIncoming(PtrNext, While);
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// Condition for the while loop.
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auto Data = Builder.CreateLoad(PtrPhi);
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auto Cmp = Builder.CreateICmpEQ(Data, CharZero);
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Builder.CreateCondBr(Cmp, WhileDone, While);
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// Add one to the computed length.
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Builder.SetInsertPoint(WhileDone, WhileDone->begin());
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auto Begin = Builder.CreatePtrToInt(Str, Int64Ty);
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auto End = Builder.CreatePtrToInt(PtrPhi, Int64Ty);
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auto Len = Builder.CreateSub(End, Begin);
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Len = Builder.CreateAdd(Len, One);
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// Final join.
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BranchInst::Create(Join, WhileDone);
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Builder.SetInsertPoint(Join, Join->begin());
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auto LenPhi = Builder.CreatePHI(Len->getType(), 2);
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LenPhi->addIncoming(Len, WhileDone);
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LenPhi->addIncoming(Zero, Prev);
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return LenPhi;
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}
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static Value *callAppendStringN(IRBuilder<> &Builder, Value *Desc, Value *Str,
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Value *Length, bool isLast) {
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auto Int64Ty = Builder.getInt64Ty();
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auto CharPtrTy = Builder.getInt8PtrTy();
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auto Int32Ty = Builder.getInt32Ty();
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auto M = Builder.GetInsertBlock()->getModule();
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auto Fn = M->getOrInsertFunction("__ockl_printf_append_string_n", Int64Ty,
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Int64Ty, CharPtrTy, Int64Ty, Int32Ty);
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auto IsLastInt32 = Builder.getInt32(isLast);
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return Builder.CreateCall(Fn, {Desc, Str, Length, IsLastInt32});
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}
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static Value *appendString(IRBuilder<> &Builder, Value *Desc, Value *Arg,
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bool IsLast) {
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auto Length = getStrlenWithNull(Builder, Arg);
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return callAppendStringN(Builder, Desc, Arg, Length, IsLast);
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}
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static Value *processArg(IRBuilder<> &Builder, Value *Desc, Value *Arg,
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bool SpecIsCString, bool IsLast) {
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if (SpecIsCString && isCString(Arg)) {
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return appendString(Builder, Desc, Arg, IsLast);
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}
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// If the format specifies a string but the argument is not, the frontend will
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// have printed a warning. We just rely on undefined behaviour and send the
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// argument anyway.
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return appendArg(Builder, Desc, Arg, IsLast);
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}
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// Scan the format string to locate all specifiers, and mark the ones that
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// specify a string, i.e, the "%s" specifier with optional '*' characters.
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static void locateCStrings(SparseBitVector<8> &BV, Value *Fmt) {
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StringRef Str;
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if (!getConstantStringInfo(Fmt, Str) || Str.empty())
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return;
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static const char ConvSpecifiers[] = "diouxXfFeEgGaAcspn";
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size_t SpecPos = 0;
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// Skip the first argument, the format string.
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unsigned ArgIdx = 1;
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while ((SpecPos = Str.find_first_of('%', SpecPos)) != StringRef::npos) {
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if (Str[SpecPos + 1] == '%') {
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SpecPos += 2;
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continue;
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}
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auto SpecEnd = Str.find_first_of(ConvSpecifiers, SpecPos);
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if (SpecEnd == StringRef::npos)
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return;
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auto Spec = Str.slice(SpecPos, SpecEnd + 1);
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ArgIdx += Spec.count('*');
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if (Str[SpecEnd] == 's') {
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BV.set(ArgIdx);
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}
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SpecPos = SpecEnd + 1;
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++ArgIdx;
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}
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}
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Value *llvm::emitAMDGPUPrintfCall(IRBuilder<> &Builder,
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ArrayRef<Value *> Args) {
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auto NumOps = Args.size();
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assert(NumOps >= 1);
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auto Fmt = Args[0];
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SparseBitVector<8> SpecIsCString;
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locateCStrings(SpecIsCString, Fmt);
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auto Desc = callPrintfBegin(Builder, Builder.getIntN(64, 0));
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Desc = appendString(Builder, Desc, Fmt, NumOps == 1);
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// FIXME: This invokes hostcall once for each argument. We can pack up to
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// seven scalar printf arguments in a single hostcall. See the signature of
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// callAppendArgs().
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for (unsigned int i = 1; i != NumOps; ++i) {
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bool IsLast = i == NumOps - 1;
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bool IsCString = SpecIsCString.test(i);
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Desc = processArg(Builder, Desc, Args[i], IsCString, IsLast);
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}
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return Builder.CreateTrunc(Desc, Builder.getInt32Ty());
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}
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