1 //===- LowerAtomic.cpp - Lower atomic intrinsics --------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass lowers atomic intrinsics to non-atomic form for use in a known
11 // non-preemptible environment.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #define DEBUG_TYPE "loweratomic"
16 #include "llvm/Transforms/Scalar.h"
17 #include "llvm/Function.h"
18 #include "llvm/IntrinsicInst.h"
19 #include "llvm/Pass.h"
20 #include "llvm/Support/IRBuilder.h"
21 using namespace llvm;
22
LowerAtomicIntrinsic(IntrinsicInst * II)23 static bool LowerAtomicIntrinsic(IntrinsicInst *II) {
24 IRBuilder<> Builder(II->getParent(), II);
25 unsigned IID = II->getIntrinsicID();
26 switch (IID) {
27 case Intrinsic::memory_barrier:
28 break;
29
30 case Intrinsic::atomic_load_add:
31 case Intrinsic::atomic_load_sub:
32 case Intrinsic::atomic_load_and:
33 case Intrinsic::atomic_load_nand:
34 case Intrinsic::atomic_load_or:
35 case Intrinsic::atomic_load_xor:
36 case Intrinsic::atomic_load_max:
37 case Intrinsic::atomic_load_min:
38 case Intrinsic::atomic_load_umax:
39 case Intrinsic::atomic_load_umin: {
40 Value *Ptr = II->getArgOperand(0), *Delta = II->getArgOperand(1);
41
42 LoadInst *Orig = Builder.CreateLoad(Ptr);
43 Value *Res = NULL;
44 switch (IID) {
45 default: assert(0 && "Unrecognized atomic modify operation");
46 case Intrinsic::atomic_load_add:
47 Res = Builder.CreateAdd(Orig, Delta);
48 break;
49 case Intrinsic::atomic_load_sub:
50 Res = Builder.CreateSub(Orig, Delta);
51 break;
52 case Intrinsic::atomic_load_and:
53 Res = Builder.CreateAnd(Orig, Delta);
54 break;
55 case Intrinsic::atomic_load_nand:
56 Res = Builder.CreateNot(Builder.CreateAnd(Orig, Delta));
57 break;
58 case Intrinsic::atomic_load_or:
59 Res = Builder.CreateOr(Orig, Delta);
60 break;
61 case Intrinsic::atomic_load_xor:
62 Res = Builder.CreateXor(Orig, Delta);
63 break;
64 case Intrinsic::atomic_load_max:
65 Res = Builder.CreateSelect(Builder.CreateICmpSLT(Orig, Delta),
66 Delta, Orig);
67 break;
68 case Intrinsic::atomic_load_min:
69 Res = Builder.CreateSelect(Builder.CreateICmpSLT(Orig, Delta),
70 Orig, Delta);
71 break;
72 case Intrinsic::atomic_load_umax:
73 Res = Builder.CreateSelect(Builder.CreateICmpULT(Orig, Delta),
74 Delta, Orig);
75 break;
76 case Intrinsic::atomic_load_umin:
77 Res = Builder.CreateSelect(Builder.CreateICmpULT(Orig, Delta),
78 Orig, Delta);
79 break;
80 }
81 Builder.CreateStore(Res, Ptr);
82
83 II->replaceAllUsesWith(Orig);
84 break;
85 }
86
87 case Intrinsic::atomic_swap: {
88 Value *Ptr = II->getArgOperand(0), *Val = II->getArgOperand(1);
89 LoadInst *Orig = Builder.CreateLoad(Ptr);
90 Builder.CreateStore(Val, Ptr);
91 II->replaceAllUsesWith(Orig);
92 break;
93 }
94
95 case Intrinsic::atomic_cmp_swap: {
96 Value *Ptr = II->getArgOperand(0), *Cmp = II->getArgOperand(1);
97 Value *Val = II->getArgOperand(2);
98
99 LoadInst *Orig = Builder.CreateLoad(Ptr);
100 Value *Equal = Builder.CreateICmpEQ(Orig, Cmp);
101 Value *Res = Builder.CreateSelect(Equal, Val, Orig);
102 Builder.CreateStore(Res, Ptr);
103 II->replaceAllUsesWith(Orig);
104 break;
105 }
106
107 default:
108 return false;
109 }
110
111 assert(II->use_empty() &&
112 "Lowering should have eliminated any uses of the intrinsic call!");
113 II->eraseFromParent();
114
115 return true;
116 }
117
118 namespace {
119 struct LowerAtomic : public BasicBlockPass {
120 static char ID;
LowerAtomic__anonda9229de0111::LowerAtomic121 LowerAtomic() : BasicBlockPass(ID) {
122 initializeLowerAtomicPass(*PassRegistry::getPassRegistry());
123 }
runOnBasicBlock__anonda9229de0111::LowerAtomic124 bool runOnBasicBlock(BasicBlock &BB) {
125 bool Changed = false;
126 for (BasicBlock::iterator DI = BB.begin(), DE = BB.end(); DI != DE; )
127 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(DI++))
128 Changed |= LowerAtomicIntrinsic(II);
129 return Changed;
130 }
131 };
132 }
133
134 char LowerAtomic::ID = 0;
135 INITIALIZE_PASS(LowerAtomic, "loweratomic",
136 "Lower atomic intrinsics to non-atomic form",
137 false, false)
138
createLowerAtomicPass()139 Pass *llvm::createLowerAtomicPass() { return new LowerAtomic(); }
140