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| 1 //===- RewriteAsmDirectives.cpp - Handle Architecture-Independent Assembly-===// | |
| 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 rewrites any inline assembly directive which is portable | |
| 11 // into LLVM bitcode. | |
| 12 // | |
| 13 //===----------------------------------------------------------------------===// | |
| 14 | |
| 15 #include "llvm/ADT/Twine.h" | |
| 16 #include "llvm/IR/Function.h" | |
| 17 #include "llvm/IR/InlineAsm.h" | |
| 18 #include "llvm/IR/Instructions.h" | |
| 19 #include "llvm/IR/Module.h" | |
| 20 #include "llvm/InstVisitor.h" | |
| 21 #include "llvm/Pass.h" | |
| 22 #include <string> | |
| 23 | |
| 24 using namespace llvm; | |
| 25 | |
| 26 namespace { | |
| 27 class RewriteAsmDirectives : public FunctionPass { | |
| 28 public: | |
| 29 static char ID; // Pass identification, replacement for typeid | |
| 30 RewriteAsmDirectives() : FunctionPass(ID) { | |
| 31 initializeRewriteAsmDirectivesPass(*PassRegistry::getPassRegistry()); | |
| 32 } | |
| 33 | |
| 34 virtual bool runOnFunction(Function &F); | |
| 35 }; | |
| 36 | |
| 37 class AsmDirectivesVisitor : public InstVisitor<AsmDirectivesVisitor> { | |
| 38 public: | |
| 39 AsmDirectivesVisitor(Function &F) | |
| 40 : F(F), C(F.getParent()->getContext()), ModifiedFunction(false) {} | |
| 41 ~AsmDirectivesVisitor() {} | |
| 42 bool modifiedFunction() const { return ModifiedFunction; } | |
| 43 | |
| 44 /// Only Call Instructions are ever inline assembly directives. | |
| 45 void visitCallInst(CallInst &CI); | |
| 46 | |
| 47 private: | |
| 48 Function &F; | |
| 49 LLVMContext &C; | |
| 50 bool ModifiedFunction; | |
| 51 | |
| 52 AsmDirectivesVisitor() LLVM_DELETED_FUNCTION; | |
| 53 AsmDirectivesVisitor(const AsmDirectivesVisitor &) LLVM_DELETED_FUNCTION; | |
| 54 AsmDirectivesVisitor &operator=(const AsmDirectivesVisitor &) LLVM_DELETED_FUN
CTION; | |
| 55 }; | |
| 56 } | |
| 57 | |
| 58 char RewriteAsmDirectives::ID = 0; | |
| 59 INITIALIZE_PASS( | |
| 60 RewriteAsmDirectives, "rewrite-asm-directives", | |
| 61 "rewrite portable inline assembly directives into non-asm LLVM IR", | |
| 62 false, false) | |
| 63 | |
| 64 bool RewriteAsmDirectives::runOnFunction(Function &F) { | |
| 65 AsmDirectivesVisitor AV(F); | |
| 66 AV.visit(F); | |
| 67 return AV.modifiedFunction(); | |
| 68 } | |
| 69 | |
| 70 void AsmDirectivesVisitor::visitCallInst(CallInst &CI) { | |
| 71 if (!CI.isInlineAsm()) | |
| 72 return; | |
| 73 | |
| 74 Instruction *Replacement = NULL; | |
| 75 | |
| 76 InlineAsm *IA = cast<InlineAsm>(CI.getCalledValue()); | |
| 77 std::string AsmStr(IA->getAsmString()); | |
| 78 std::string ConstraintStr(IA->getConstraintString()); | |
| 79 Type *T = CI.getType(); | |
| 80 | |
| 81 bool isEmptyAsm = AsmStr.empty(); | |
| 82 // Different triples will encode "touch everything" differently, e.g.: | |
| 83 // - le32-unknown-nacl has "~{memory}". | |
| 84 // - x86 "~{memory},~{dirflag},~{fpsr},~{flags}". | |
| 85 // The following code therefore only searches for memory: this pass | |
| 86 // deals with portable assembly, touching anything else than memory in | |
| 87 // an empty assembly statement is meaningless. | |
| 88 bool touchesMemory = ConstraintStr.find("~{memory}") != std::string::npos; | |
| 89 | |
| 90 if (T->isVoidTy() && IA->hasSideEffects() && isEmptyAsm && touchesMemory) { | |
| 91 // asm("":::"memory") => fence seq_cst | |
| 92 // This transformation is safe and strictly stronger: the former is | |
| 93 // purely a compiler fence, whereas the latter is a compiler fence | |
| 94 // as well as a hardware fence which orders all loads and stores on | |
| 95 // the current thread of execution. | |
| 96 Replacement = new FenceInst(C, SequentiallyConsistent, CrossThread, &CI); | |
| 97 } | |
| 98 | |
| 99 if (Replacement) { | |
| 100 Replacement->setDebugLoc(CI.getDebugLoc()); | |
| 101 CI.replaceAllUsesWith(Replacement); | |
| 102 CI.eraseFromParent(); | |
| 103 ModifiedFunction = true; | |
| 104 } | |
| 105 } | |
| 106 | |
| 107 namespace llvm { | |
| 108 FunctionPass *createRewriteAsmDirectivesPass() { | |
| 109 return new RewriteAsmDirectives(); | |
| 110 } | |
| 111 } | |
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Chromium Code Reviews
Issue 22474008:
Add the new @llvm.nacl.atomic.fence.all intrinsic (Closed)
Base URL: http://git.chromium.org/native_client/pnacl-llvm.git@master