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
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
|
/*========================== begin_copyright_notice ============================
Copyright (C) 2025 Intel Corporation
SPDX-License-Identifier: MIT
============================= end_copyright_notice ===========================*/
#include "SinkPointerConstAdd.h"
#include "common/LLVMWarningsPush.hpp"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/IRBuilder.h"
#include "common/LLVMWarningsPop.hpp"
#include "GenISAIntrinsics/GenIntrinsicInst.h"
// Simple pass which sinks constant add operations in pointer calculations
// It changes following pattern:
// %addr_part1 = <base1> + const
// %addr_part2 = <base2> + %addr_part1
// %ptr = inttoptr %addr_part2
// to:
// %addr_part1 = <base1> + <base2>
// %addr_part2 = <addr_part1> + const
// %ptr = inttoptr %addr_part2
// This helps other optimizations like GVN to eliminate redundant calculations.
using namespace llvm;
class SinkPointerConstAddPass : public llvm::FunctionPass {
public:
SinkPointerConstAddPass() : llvm::FunctionPass(ID) {
initializeSinkPointerConstAddPassPass(*llvm::PassRegistry::getPassRegistry());
}
virtual bool runOnFunction(llvm::Function &F) override;
virtual void getAnalysisUsage(llvm::AnalysisUsage &AU) const override { AU.setPreservesCFG(); }
virtual llvm::StringRef getPassName() const override { return "SinkPointerConstAdd"; }
static char ID;
private:
bool getConstantOffset(llvm::Value *value, std::vector<llvm::Instruction *> &zexts, int &offset);
void zextToSext(std::vector<llvm::Instruction *> &zexts);
bool skipZextToSext(llvm::Instruction *op, llvm::BasicBlock *parentBB);
};
#define PASS_FLAG "igc-sink-ptr-const-add"
#define PASS_DESCRIPTION "Sink pointer const add"
#define PASS_CFG_ONLY false
#define PASS_ANALYSIS false
IGC_INITIALIZE_PASS(SinkPointerConstAddPass, PASS_FLAG, PASS_DESCRIPTION, PASS_CFG_ONLY, PASS_ANALYSIS)
bool SinkPointerConstAddPass::getConstantOffset(llvm::Value *value, std::vector<llvm::Instruction *> &zexts,
int &offset) {
// Recursively search for constant add operations - this will stop after the first const add found,
// and should be called repeatedly until no more const adds can be sunk.
if (value->getNumUses() > 1) {
return false; // We cannot sink constant add if the value is used more than once.
}
if (llvm::Instruction *instr = llvm::dyn_cast<llvm::Instruction>(value)) {
if (instr->getOpcode() == llvm::Instruction::Trunc || instr->getOpcode() == llvm::Instruction::ZExt ||
instr->getOpcode() == llvm::Instruction::SExt) {
// Skip cast instructions
llvm::Instruction *op = llvm::dyn_cast<llvm::Instruction>(instr->getOperand(0));
// This is a simple pass, only sink within the same basic block
if (op && instr->getParent() == op->getParent()) {
// Collect zext instructions for later processing
if (instr->getOpcode() == llvm::Instruction::ZExt) {
zexts.push_back(instr);
}
return getConstantOffset(instr->getOperand(0), zexts, offset);
} else {
return false;
}
} else if (instr->getOpcode() == llvm::Instruction::Add || instr->getOpcode() == llvm::Instruction::Sub) {
if (llvm::ConstantInt *constInt = llvm::dyn_cast<llvm::ConstantInt>(instr->getOperand(1))) {
offset = instr->getOpcode() == llvm::Instruction::Add ? offset + constInt->getSExtValue()
: offset - constInt->getSExtValue();
instr->replaceAllUsesWith(instr->getOperand(0));
instr->eraseFromParent();
return true;
} else if (llvm::ConstantInt *constInt = llvm::dyn_cast<llvm::ConstantInt>(instr->getOperand(0))) {
if (instr->getOpcode() == llvm::Instruction::Sub) {
// Cannot sink constant on the left side of subtraction
return false;
}
offset += constInt->getSExtValue();
instr->replaceAllUsesWith(instr->getOperand(1));
instr->eraseFromParent();
return true;
} else {
llvm::Instruction *op0 = llvm::dyn_cast<llvm::Instruction>(instr->getOperand(0));
llvm::Instruction *op1 = llvm::dyn_cast<llvm::Instruction>(instr->getOperand(1));
// This is a simple pass, only sink within the same basic block
return (op0 && instr->getParent() == op0->getParent() && getConstantOffset(op0, zexts, offset)) ? true
: (op1 && instr->getParent() == op1->getParent()) ? getConstantOffset(op1, zexts, offset)
: false;
}
}
}
return false;
}
bool SinkPointerConstAddPass::skipZextToSext(llvm::Instruction *op, llvm::BasicBlock *parentBB) {
// This is a simple pass, only sink within the same basic block
if (op && parentBB == op->getParent()) {
// Do not change zext of pushed constants or loaded values - UMD provides unsigned offsets
if (llvm::GenIntrinsicInst *instr = llvm::dyn_cast<llvm::GenIntrinsicInst>(op)) {
if (instr->getIntrinsicID() == llvm::GenISAIntrinsic::GenISA_RuntimeValue) {
return true;
}
} else if (llvm::dyn_cast<llvm::Argument>(op) || llvm::dyn_cast<llvm::LoadInst>(op)) {
return true;
} else if (llvm::BinaryOperator *bo = llvm::dyn_cast<BinaryOperator>(op)) {
llvm::ConstantInt *cOp0 = llvm::dyn_cast<llvm::ConstantInt>(bo->getOperand(0));
llvm::ConstantInt *cOp1 = llvm::dyn_cast<llvm::ConstantInt>(bo->getOperand(1));
if ((cOp0 && cOp0->isNegative()) || (cOp1 && cOp1->isNegative())) {
return false;
} else if (bo->getOpcode() == llvm::Instruction::Sub) {
return false;
} else {
return (skipZextToSext(llvm::dyn_cast<llvm::Instruction>(bo->getOperand(0)), parentBB) &&
skipZextToSext(llvm::dyn_cast<llvm::Instruction>(bo->getOperand(1)), parentBB));
}
} else {
return false;
}
}
return true;
}
void SinkPointerConstAddPass::zextToSext(std::vector<llvm::Instruction *> &zexts) {
// Remove duplicates
std::sort(zexts.begin(), zexts.end());
zexts.erase(std::unique(zexts.begin(), zexts.end()), zexts.end());
// Convert zext instructions to sext instructions
for (auto &zext : zexts) {
llvm::Instruction *op = llvm::dyn_cast<llvm::Instruction>(zext->getOperand(0));
if (skipZextToSext(op, zext->getParent())) {
continue;
}
llvm::IRBuilder<> builder(zext);
llvm::Value *sext = builder.CreateSExt(zext->getOperand(0), zext->getType());
zext->replaceAllUsesWith(sext);
zext->eraseFromParent();
}
}
bool SinkPointerConstAddPass::runOnFunction(llvm::Function &F) {
bool changed = false;
std::vector<llvm::IntToPtrInst *> intToPtrInsts;
intToPtrInsts.reserve(50);
// Collect all inttoptr instructions first
for (llvm::BasicBlock &BB : F) {
for (llvm::Instruction &inst : BB) {
if (llvm::IntToPtrInst *intrinsic = llvm::dyn_cast<llvm::IntToPtrInst>(&inst)) {
intToPtrInsts.push_back(intrinsic);
}
}
}
for (auto &intrinsic : intToPtrInsts) {
int offset = 0;
bool localChanged = false;
std::vector<llvm::Instruction *> zexts;
// Keep sinking constant adds until no more can be sunk
while (getConstantOffset(intrinsic->getOperand(0), zexts, offset)) {
localChanged = true;
changed = true;
}
if (localChanged) {
// In some cases, sinking constant add may introduce negative values in pointer calculations.
// Convert affected zext instructions to sext instructions to avoid potential issues.
zextToSext(zexts);
}
// If we found any constant offset, create new pointer calculation
if (offset != 0) {
llvm::IRBuilder<> builder(intrinsic);
llvm::Value *newPtr =
builder.CreateIntToPtr(builder.CreateAdd(intrinsic->getOperand(0),
llvm::ConstantInt::get(intrinsic->getOperand(0)->getType(), offset)),
intrinsic->getType());
intrinsic->replaceAllUsesWith(newPtr);
intrinsic->eraseFromParent();
}
}
return changed;
}
char SinkPointerConstAddPass::ID = 0;
llvm::FunctionPass *createSinkPointerConstAddPass() { return new SinkPointerConstAddPass(); }
|
