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
diff --git a/lib/CodeGen/CGExprCXX.cpp b/lib/CodeGen/CGExprCXX.cpp
index cc34b3d..d3e7919 100644
--- a/lib/CodeGen/CGExprCXX.cpp
+++ b/lib/CodeGen/CGExprCXX.cpp
@@ -440,7 +440,7 @@
// 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 @@
TypeSize.getQuantity()));
// Branch on the overflow bit to the overflow block, which is lazily created.
llvm::Value *DidOverflow = CGF.Builder.CreateExtractValue(MulRes, 1);
-
- llvm::BasicBlock *NormalBB = CGF.createBasicBlock("no_overflow");
-
- CGF.Builder.CreateCondBr(DidOverflow, CGF.getThrowLengthErrorBB(), NormalBB);
- CGF.EmitBlock(NormalBB);
-
// 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, 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);
+
+ 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 5e5e2a4..eb6c436 100644
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/lib/CodeGen/CodeGenFunction.cpp
@@ -36,7 +36,7 @@
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 @@
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 @@
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<const llvm::Type*> 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 1a117ca..f236eb4 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -656,7 +656,7 @@
llvm::BasicBlock *TerminateLandingPad;
llvm::BasicBlock *TerminateHandler;
- llvm::BasicBlock *TrapBB, *ThrowLengthErrorBB;
+ llvm::BasicBlock *TrapBB;
public:
CodeGenFunction(CodeGenModule &cgm);
@@ -1544,10 +1544,6 @@
/// 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);