1 files changed, 246 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/Utils/AMDGPUEmitPrintf.cpp b/llvm/lib/Transforms/Utils/AMDGPUEmitPrintf.cpp
new file mode 100644
index 0000000000000..84a66e1e96d2c
--- /dev/null
+++ b/llvm/lib/Transforms/Utils/AMDGPUEmitPrintf.cpp
@@ -0,0 +1,246 @@
+//===- AMDGPUEmitPrintf.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
+//
+//===----------------------------------------------------------------------===//
+//
+// Utility function to lower a printf call into a series of device
+// library calls on the AMDGPU target.
+//
+// WARNING: This file knows about certain library functions. It recognizes them
+// by name, and hardwires knowledge of their semantics.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/AMDGPUEmitPrintf.h"
+#include "llvm/ADT/SparseBitVector.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/IRBuilder.h"
+
+#include <iostream>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "amdgpu-emit-printf"
+
+static bool isCString(const Value *Arg) {
+  auto Ty = Arg->getType();
+  auto PtrTy = dyn_cast<PointerType>(Ty);
+  if (!PtrTy)
+    return false;
+
+  auto IntTy = dyn_cast<IntegerType>(PtrTy->getElementType());
+  if (!IntTy)
+    return false;
+
+  return IntTy->getBitWidth() == 8;
+}
+
+static Value *fitArgInto64Bits(IRBuilder<> &Builder, Value *Arg) {
+  auto Int64Ty = Builder.getInt64Ty();
+  auto Ty = Arg->getType();
+
+  if (auto IntTy = dyn_cast<IntegerType>(Ty)) {
+    switch (IntTy->getBitWidth()) {
+    case 32:
+      return Builder.CreateZExt(Arg, Int64Ty);
+    case 64:
+      return Arg;
+    }
+  }
+
+  if (Ty->getTypeID() == Type::DoubleTyID) {
+    return Builder.CreateBitCast(Arg, Int64Ty);
+  }
+
+  if (isa<PointerType>(Ty)) {
+    return Builder.CreatePtrToInt(Arg, Int64Ty);
+  }
+
+  llvm_unreachable("unexpected type");
+}
+
+static Value *callPrintfBegin(IRBuilder<> &Builder, Value *Version) {
+  auto Int64Ty = Builder.getInt64Ty();
+  auto M = Builder.GetInsertBlock()->getModule();
+  auto Fn = M->getOrInsertFunction("__ockl_printf_begin", Int64Ty, Int64Ty);
+  return Builder.CreateCall(Fn, Version);
+}
+
+static Value *callAppendArgs(IRBuilder<> &Builder, Value *Desc, int NumArgs,
+                             Value *Arg0, Value *Arg1, Value *Arg2, Value *Arg3,
+                             Value *Arg4, Value *Arg5, Value *Arg6,
+                             bool IsLast) {
+  auto Int64Ty = Builder.getInt64Ty();
+  auto Int32Ty = Builder.getInt32Ty();
+  auto M = Builder.GetInsertBlock()->getModule();
+  auto Fn = M->getOrInsertFunction("__ockl_printf_append_args", Int64Ty,
+                                   Int64Ty, Int32Ty, Int64Ty, Int64Ty, Int64Ty,
+                                   Int64Ty, Int64Ty, Int64Ty, Int64Ty, Int32Ty);
+  auto IsLastValue = Builder.getInt32(IsLast);
+  auto NumArgsValue = Builder.getInt32(NumArgs);
+  return Builder.CreateCall(Fn, {Desc, NumArgsValue, Arg0, Arg1, Arg2, Arg3,
+                                 Arg4, Arg5, Arg6, IsLastValue});
+}
+
+static Value *appendArg(IRBuilder<> &Builder, Value *Desc, Value *Arg,
+                        bool IsLast) {
+  auto Arg0 = fitArgInto64Bits(Builder, Arg);
+  auto Zero = Builder.getInt64(0);
+  return callAppendArgs(Builder, Desc, 1, Arg0, Zero, Zero, Zero, Zero, Zero,
+                        Zero, IsLast);
+}
+
+// The device library does not provide strlen, so we build our own loop
+// here. While we are at it, we also include the terminating null in the length.
+static Value *getStrlenWithNull(IRBuilder<> &Builder, Value *Str) {
+  auto *Prev = Builder.GetInsertBlock();
+  Module *M = Prev->getModule();
+
+  auto CharZero = Builder.getInt8(0);
+  auto One = Builder.getInt64(1);
+  auto Zero = Builder.getInt64(0);
+  auto Int64Ty = Builder.getInt64Ty();
+
+  // The length is either zero for a null pointer, or the computed value for an
+  // actual string. We need a join block for a phi that represents the final
+  // value.
+  //
+  //  Strictly speaking, the zero does not matter since
+  // __ockl_printf_append_string_n ignores the length if the pointer is null.
+  BasicBlock *Join = nullptr;
+  if (Prev->getTerminator()) {
+    Join = Prev->splitBasicBlock(Builder.GetInsertPoint(),
+                                 "strlen.join");
+    Prev->getTerminator()->eraseFromParent();
+  } else {
+    Join = BasicBlock::Create(M->getContext(), "strlen.join",
+                              Prev->getParent());
+  }
+  BasicBlock *While =
+      BasicBlock::Create(M->getContext(), "strlen.while",
+                         Prev->getParent(), Join);
+  BasicBlock *WhileDone = BasicBlock::Create(
+      M->getContext(), "strlen.while.done",
+      Prev->getParent(), Join);
+
+  // Emit an early return for when the pointer is null.
+  Builder.SetInsertPoint(Prev);
+  auto CmpNull =
+      Builder.CreateICmpEQ(Str, Constant::getNullValue(Str->getType()));
+  BranchInst::Create(Join, While, CmpNull, Prev);
+
+  // Entry to the while loop.
+  Builder.SetInsertPoint(While);
+
+  auto PtrPhi = Builder.CreatePHI(Str->getType(), 2);
+  PtrPhi->addIncoming(Str, Prev);
+  auto PtrNext = Builder.CreateGEP(PtrPhi, One);
+  PtrPhi->addIncoming(PtrNext, While);
+
+  // Condition for the while loop.
+  auto Data = Builder.CreateLoad(PtrPhi);
+  auto Cmp = Builder.CreateICmpEQ(Data, CharZero);
+  Builder.CreateCondBr(Cmp, WhileDone, While);
+
+  // Add one to the computed length.
+  Builder.SetInsertPoint(WhileDone, WhileDone->begin());
+  auto Begin = Builder.CreatePtrToInt(Str, Int64Ty);
+  auto End = Builder.CreatePtrToInt(PtrPhi, Int64Ty);
+  auto Len = Builder.CreateSub(End, Begin);
+  Len = Builder.CreateAdd(Len, One);
+
+  // Final join.
+  BranchInst::Create(Join, WhileDone);
+  Builder.SetInsertPoint(Join, Join->begin());
+  auto LenPhi = Builder.CreatePHI(Len->getType(), 2);
+  LenPhi->addIncoming(Len, WhileDone);
+  LenPhi->addIncoming(Zero, Prev);
+
+  return LenPhi;
+}
+
+static Value *callAppendStringN(IRBuilder<> &Builder, Value *Desc, Value *Str,
+                                Value *Length, bool isLast) {
+  auto Int64Ty = Builder.getInt64Ty();
+  auto CharPtrTy = Builder.getInt8PtrTy();
+  auto Int32Ty = Builder.getInt32Ty();
+  auto M = Builder.GetInsertBlock()->getModule();
+  auto Fn = M->getOrInsertFunction("__ockl_printf_append_string_n", Int64Ty,
+                                   Int64Ty, CharPtrTy, Int64Ty, Int32Ty);
+  auto IsLastInt32 = Builder.getInt32(isLast);
+  return Builder.CreateCall(Fn, {Desc, Str, Length, IsLastInt32});
+}
+
+static Value *appendString(IRBuilder<> &Builder, Value *Desc, Value *Arg,
+                           bool IsLast) {
+  auto Length = getStrlenWithNull(Builder, Arg);
+  return callAppendStringN(Builder, Desc, Arg, Length, IsLast);
+}
+
+static Value *processArg(IRBuilder<> &Builder, Value *Desc, Value *Arg,
+                         bool SpecIsCString, bool IsLast) {
+  if (SpecIsCString && isCString(Arg)) {
+    return appendString(Builder, Desc, Arg, IsLast);
+  }
+  // If the format specifies a string but the argument is not, the frontend will
+  // have printed a warning. We just rely on undefined behaviour and send the
+  // argument anyway.
+  return appendArg(Builder, Desc, Arg, IsLast);
+}
+
+// Scan the format string to locate all specifiers, and mark the ones that
+// specify a string, i.e, the "%s" specifier with optional '*' characters.
+static void locateCStrings(SparseBitVector<8> &BV, Value *Fmt) {
+  StringRef Str;
+  if (!getConstantStringInfo(Fmt, Str) || Str.empty())
+    return;
+
+  static const char ConvSpecifiers[] = "diouxXfFeEgGaAcspn";
+  size_t SpecPos = 0;
+  // Skip the first argument, the format string.
+  unsigned ArgIdx = 1;
+
+  while ((SpecPos = Str.find_first_of('%', SpecPos)) != StringRef::npos) {
+    if (Str[SpecPos + 1] == '%') {
+      SpecPos += 2;
+      continue;
+    }
+    auto SpecEnd = Str.find_first_of(ConvSpecifiers, SpecPos);
+    if (SpecEnd == StringRef::npos)
+      return;
+    auto Spec = Str.slice(SpecPos, SpecEnd + 1);
+    ArgIdx += Spec.count('*');
+    if (Str[SpecEnd] == 's') {
+      BV.set(ArgIdx);
+    }
+    SpecPos = SpecEnd + 1;
+    ++ArgIdx;
+  }
+}
+
+Value *llvm::emitAMDGPUPrintfCall(IRBuilder<> &Builder,
+                                  ArrayRef<Value *> Args) {
+  auto NumOps = Args.size();
+  assert(NumOps >= 1);
+
+  auto Fmt = Args[0];
+  SparseBitVector<8> SpecIsCString;
+  locateCStrings(SpecIsCString, Fmt);
+
+  auto Desc = callPrintfBegin(Builder, Builder.getIntN(64, 0));
+  Desc = appendString(Builder, Desc, Fmt, NumOps == 1);
+
+  // FIXME: This invokes hostcall once for each argument. We can pack up to
+  // seven scalar printf arguments in a single hostcall. See the signature of
+  // callAppendArgs().
+  for (unsigned int i = 1; i != NumOps; ++i) {
+    bool IsLast = i == NumOps - 1;
+    bool IsCString = SpecIsCString.test(i);
+    Desc = processArg(Builder, Desc, Args[i], IsCString, IsLast);
+  }
+
+  return Builder.CreateTrunc(Desc, Builder.getInt32Ty());
+}