From 83252dcfe61aaebcb6bc117e71dc12968729513f Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Tue, 20 Jul 2010 21:07:09 +0000 Subject: [PATCH] Follow the implementation approach suggested by PR6687, which generates more efficient and more obviously conformant code. We now test for overflow of the multiply then force the result to -1 if so. On X86, this generates nice code like this: __Z4testl: ## @_Z4testl ## BB#0: ## %entry subl $12, %esp movl $4, %eax mull 16(%esp) testl %edx, %edx movl $-1, %ecx cmovel %eax, %ecx movl %ecx, (%esp) call __Znam addl $12, %esp ret git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@108927 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/CGExprCXX.cpp | 21 +++++++++++++---- lib/CodeGen/CodeGenFunction.cpp | 40 +------------------------------- lib/CodeGen/CodeGenFunction.h | 6 +---- test/CodeGenCXX/operator-new.cpp | 7 +++--- 4 files changed, 21 insertions(+), 53 deletions(-) diff --git a/lib/CodeGen/CGExprCXX.cpp b/lib/CodeGen/CGExprCXX.cpp index cc34b3d75c..d3e7919224 100644 --- a/lib/CodeGen/CGExprCXX.cpp +++ b/lib/CodeGen/CGExprCXX.cpp @@ -440,7 +440,7 @@ static llvm::Value *EmitCXXNewAllocSize(ASTContext &Context, // new double[n] // where n is 2^30 on a 32-bit machine or 2^62 on a 64-bit machine. Because // of this, we need to detect the overflow and ensure that an exception is - // called by invoking std::__throw_length_error. + // called by forcing the size to -1 on overflow. llvm::Value *UMulF = CGF.CGM.getIntrinsic(llvm::Intrinsic::umul_with_overflow, &SizeTy, 1); llvm::Value *MulRes = CGF.Builder.CreateCall2(UMulF, NumElements, @@ -448,15 +448,26 @@ static llvm::Value *EmitCXXNewAllocSize(ASTContext &Context, TypeSize.getQuantity())); // Branch on the overflow bit to the overflow block, which is lazily created. llvm::Value *DidOverflow = CGF.Builder.CreateExtractValue(MulRes, 1); + // Get the normal result of the multiplication. + llvm::Value *V = CGF.Builder.CreateExtractValue(MulRes, 0); llvm::BasicBlock *NormalBB = CGF.createBasicBlock("no_overflow"); + llvm::BasicBlock *OverflowBB = CGF.createBasicBlock("overflow"); - CGF.Builder.CreateCondBr(DidOverflow, CGF.getThrowLengthErrorBB(), NormalBB); + CGF.Builder.CreateCondBr(DidOverflow, OverflowBB, NormalBB); + + llvm::BasicBlock *PrevBB = CGF.Builder.GetInsertBlock(); + + // We just need the overflow block to build a PHI node. + CGF.EmitBlock(OverflowBB); CGF.EmitBlock(NormalBB); - // Get the normal result of the multiplication. - llvm::Value *V = CGF.Builder.CreateExtractValue(MulRes, 0); - + llvm::PHINode *PN = CGF.Builder.CreatePHI(V->getType()); + + PN->addIncoming(V, PrevBB); + PN->addIncoming(llvm::Constant::getAllOnesValue(V->getType()), OverflowBB); + V = PN; + // And add the cookie padding if necessary. if (!CookiePadding.isZero()) V = CGF.Builder.CreateAdd(V, diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp index 5e5e2a49cc..eb6c4361be 100644 --- a/lib/CodeGen/CodeGenFunction.cpp +++ b/lib/CodeGen/CodeGenFunction.cpp @@ -36,7 +36,7 @@ CodeGenFunction::CodeGenFunction(CodeGenModule &cgm) DidCallStackSave(false), UnreachableBlock(0), CXXThisDecl(0), CXXThisValue(0), CXXVTTDecl(0), CXXVTTValue(0), ConditionalBranchLevel(0), TerminateLandingPad(0), TerminateHandler(0), - TrapBB(0), ThrowLengthErrorBB(0) { + TrapBB(0) { // Get some frequently used types. LLVMPointerWidth = Target.getPointerWidth(0); @@ -155,13 +155,6 @@ void CodeGenFunction::FinishFunction(SourceLocation EndLoc) { Builder.ClearInsertionPoint(); } - // If someone called operator new[] and needs a throw_length_error block, emit - // it at the end of the function. - if (ThrowLengthErrorBB) { - EmitBlock(ThrowLengthErrorBB); - Builder.ClearInsertionPoint(); - } - // Remove the AllocaInsertPt instruction, which is just a convenience for us. llvm::Instruction *Ptr = AllocaInsertPt; AllocaInsertPt = 0; @@ -185,37 +178,6 @@ void CodeGenFunction::FinishFunction(SourceLocation EndLoc) { EmitDeclMetadata(); } -/// getThrowLengthErrorBB - Create a basic block that will call -/// std::__throw_length_error to throw a std::length_error exception. -llvm::BasicBlock *CodeGenFunction::getThrowLengthErrorBB() { - if (ThrowLengthErrorBB) return ThrowLengthErrorBB; - - llvm::IRBuilder<>::InsertPoint SavedIP = Builder.saveIP(); - - ThrowLengthErrorBB = createBasicBlock("throw_length_error"); - Builder.SetInsertPoint(ThrowLengthErrorBB); - - // Call to void std::__throw_length_error("length_error"); - const llvm::Type *ResultType = Builder.getVoidTy(); - const llvm::Type *PtrToInt8Ty = Builder.getInt8PtrTy(); - std::vector ArgTys(1, PtrToInt8Ty); - llvm::Constant *Fn = - CGM.CreateRuntimeFunction(llvm::FunctionType::get(ResultType, ArgTys, false), - "_ZSt20__throw_length_errorPKc"); - - llvm::Value *C = CGM.GetAddrOfConstantCString("length_error"); - C = Builder.CreateStructGEP(C, 0, "arraydecay"); - llvm::CallInst *TheCall = Builder.CreateCall(Fn, C); - TheCall->setDoesNotReturn(); - - Builder.CreateUnreachable(); - - - Builder.restoreIP(SavedIP); - return ThrowLengthErrorBB; -} - - /// ShouldInstrumentFunction - Return true if the current function should be /// instrumented with __cyg_profile_func_* calls bool CodeGenFunction::ShouldInstrumentFunction() { diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h index 1a117cab96..f236eb4253 100644 --- a/lib/CodeGen/CodeGenFunction.h +++ b/lib/CodeGen/CodeGenFunction.h @@ -656,7 +656,7 @@ private: llvm::BasicBlock *TerminateLandingPad; llvm::BasicBlock *TerminateHandler; - llvm::BasicBlock *TrapBB, *ThrowLengthErrorBB; + llvm::BasicBlock *TrapBB; public: CodeGenFunction(CodeGenModule &cgm); @@ -1544,10 +1544,6 @@ public: /// generate a branch around the created basic block as necessary. llvm::BasicBlock *getTrapBB(); - /// getThrowLengthErrorBB - Create a basic block that will call - /// std::__throw_length_error to throw a std::length_error exception. - llvm::BasicBlock *getThrowLengthErrorBB(); - /// EmitCallArg - Emit a single call argument. RValue EmitCallArg(const Expr *E, QualType ArgType); diff --git a/test/CodeGenCXX/operator-new.cpp b/test/CodeGenCXX/operator-new.cpp index f5cb2fb6c5..b108d27ab9 100644 --- a/test/CodeGenCXX/operator-new.cpp +++ b/test/CodeGenCXX/operator-new.cpp @@ -23,9 +23,8 @@ void *f2(long N) { // SANE: call{{.*}}@llvm.umul.with.overflow // SANE: extractvalue -// SANE: br i1{{.*}}, label %throw_length_error, label %no_overflow +// SANE: br i1{{.*}}, label %overflow, label %no_overflow -// SANE: throw_length_error: -// SANE: call void @_ZSt20__throw_length_errorPKc -// SANE: unreachable +// SANE: = phi {{.*}} [ {{.*}}, %entry ], [ -1, %overflow ] +// SANE: call noalias i8* @_Znaj( } -- 2.40.0