1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
| //===- NVVMReflect.cpp - NVVM Emulate conditional compilation -------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This pass replaces occurrences of __nvvm_reflect("foo") and llvm.nvvm.reflect
// with an integer.
//
// We choose the value we use by looking at metadata in the module itself. Note
// that we intentionally only have one way to choose these values, because other
// parts of LLVM (particularly, InstCombineCall) rely on being able to predict
// the values chosen by this pass.
//
// If we see an unknown string, we replace its call with 0.
//
//===----------------------------------------------------------------------===//
#include "NVPTX.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_os_ostream.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Scalar.h"
#include <sstream>
#include <string>
#define NVVM_REFLECT_FUNCTION "__nvvm_reflect"
using namespace llvm;
#define DEBUG_TYPE "nvptx-reflect"
namespace llvm { void initializeNVVMReflectPass(PassRegistry &); }
namespace {
class NVVMReflect : public FunctionPass {
public:
static char ID;
unsigned int SmVersion;
NVVMReflect() : NVVMReflect(0) {}
explicit NVVMReflect(unsigned int Sm) : FunctionPass(ID), SmVersion(Sm) {
initializeNVVMReflectPass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &) override;
};
}
FunctionPass *llvm::createNVVMReflectPass(unsigned int SmVersion) {
return new NVVMReflect(SmVersion);
}
static cl::opt<bool>
NVVMReflectEnabled("nvvm-reflect-enable", cl::init(true), cl::Hidden,
cl::desc("NVVM reflection, enabled by default"));
char NVVMReflect::ID = 0;
INITIALIZE_PASS(NVVMReflect, "nvvm-reflect",
"Replace occurrences of __nvvm_reflect() calls with 0/1", false,
false)
bool NVVMReflect::runOnFunction(Function &F) {
if (!NVVMReflectEnabled)
return false;
if (F.getName() == NVVM_REFLECT_FUNCTION) {
assert(F.isDeclaration() && "_reflect function should not have a body");
assert(F.getReturnType()->isIntegerTy() &&
"_reflect's return type should be integer");
return false;
}
SmallVector<Instruction *, 4> ToRemove;
// Go through the calls in this function. Each call to __nvvm_reflect or
// llvm.nvvm.reflect should be a CallInst with a ConstantArray argument.
// First validate that. If the c-string corresponding to the ConstantArray can
// be found successfully, see if it can be found in VarMap. If so, replace the
// uses of CallInst with the value found in VarMap. If not, replace the use
// with value 0.
// The IR for __nvvm_reflect calls differs between CUDA versions.
//
// CUDA 6.5 and earlier uses this sequence:
// %ptr = tail call i8* @llvm.nvvm.ptr.constant.to.gen.p0i8.p4i8
// (i8 addrspace(4)* getelementptr inbounds
// ([8 x i8], [8 x i8] addrspace(4)* @str, i32 0, i32 0))
// %reflect = tail call i32 @__nvvm_reflect(i8* %ptr)
//
// The value returned by Sym->getOperand(0) is a Constant with a
// ConstantDataSequential operand which can be converted to string and used
// for lookup.
//
// CUDA 7.0 does it slightly differently:
// %reflect = call i32 @__nvvm_reflect(i8* addrspacecast
// (i8 addrspace(1)* getelementptr inbounds
// ([8 x i8], [8 x i8] addrspace(1)* @str, i32 0, i32 0) to i8*))
//
// In this case, we get a Constant with a GlobalVariable operand and we need
// to dig deeper to find its initializer with the string we'll use for lookup.
for (Instruction &I : instructions(F)) {
CallInst *Call = dyn_cast<CallInst>(&I);
if (!Call)
continue;
Function *Callee = Call->getCalledFunction();
if (!Callee || (Callee->getName() != NVVM_REFLECT_FUNCTION &&
Callee->getIntrinsicID() != Intrinsic::nvvm_reflect))
continue;
// FIXME: Improve error handling here and elsewhere in this pass.
assert(Call->getNumOperands() == 2 &&
"Wrong number of operands to __nvvm_reflect function");
// In cuda 6.5 and earlier, we will have an extra constant-to-generic
// conversion of the string.
const Value *Str = Call->getArgOperand(0);
if (const CallInst *ConvCall = dyn_cast<CallInst>(Str)) {
// FIXME: Add assertions about ConvCall.
Str = ConvCall->getArgOperand(0);
}
assert(isa<ConstantExpr>(Str) &&
"Format of __nvvm__reflect function not recognized");
const ConstantExpr *GEP = cast<ConstantExpr>(Str);
const Value *Sym = GEP->getOperand(0);
assert(isa<Constant>(Sym) &&
"Format of __nvvm_reflect function not recognized");
const Value *Operand = cast<Constant>(Sym)->getOperand(0);
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Operand)) {
// For CUDA-7.0 style __nvvm_reflect calls, we need to find the operand's
// initializer.
assert(GV->hasInitializer() &&
"Format of _reflect function not recognized");
const Constant *Initializer = GV->getInitializer();
Operand = Initializer;
}
assert(isa<ConstantDataSequential>(Operand) &&
"Format of _reflect function not recognized");
assert(cast<ConstantDataSequential>(Operand)->isCString() &&
"Format of _reflect function not recognized");
StringRef ReflectArg = cast<ConstantDataSequential>(Operand)->getAsString();
ReflectArg = ReflectArg.substr(0, ReflectArg.size() - 1);
LLVM_DEBUG(dbgs() << "Arg of _reflect : " << ReflectArg << "\n");
int ReflectVal = 0; // The default value is 0
if (ReflectArg == "__CUDA_FTZ") {
// Try to pull __CUDA_FTZ from the nvvm-reflect-ftz module flag. Our
// choice here must be kept in sync with AutoUpgrade, which uses the same
// technique to detect whether ftz is enabled.
if (auto *Flag = mdconst::extract_or_null<ConstantInt>(
F.getParent()->getModuleFlag("nvvm-reflect-ftz")))
ReflectVal = Flag->getSExtValue();
} else if (ReflectArg == "__CUDA_ARCH") {
ReflectVal = SmVersion * 10;
}
Call->replaceAllUsesWith(ConstantInt::get(Call->getType(), ReflectVal));
ToRemove.push_back(Call);
}
for (Instruction *I : ToRemove)
I->eraseFromParent();
return ToRemove.size() > 0;
}
|