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Factor some code to handle "load (constantexpr cast foo)" just like

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"load (cast foo)".  This allows us to compile C++ code like this:

class Bclass {
  public: virtual int operator()() { return 666; }
};

class Dclass: public Bclass {
  public: virtual int operator()() { return 667; }
} ;

int main(int argc, char** argv) {
  Dclass x;
  return x();
}

Into this:

int %main(int %argc, sbyte** %argv) {
entry:
        call void %__main( )
        ret int 667
}

Instead of this:

int %main(int %argc, sbyte** %argv) {
entry:
        %x = alloca "struct.std::bad_typeid"            ; <"struct.std::bad_typeid"*> [#uses=3]
        call void %__main( )
        %tmp.1.i.i = getelementptr "struct.std::bad_typeid"* %x, uint 0, uint 0, uint 0         ; <int (...)***> [#uses=1]
        store int (...)** getelementptr ([3 x int (...)*]*  %vtable for Bclass, int 0, long 2), int (...)*** %tmp.1.i.i
        %tmp.3.i = getelementptr "struct.std::bad_typeid"* %x, int 0, uint 0, uint 0            ; <int (...)***> [#uses=1]
        store int (...)** getelementptr ([3 x int (...)*]*  %vtable for Dclass, int 0, long 2), int (...)*** %tmp.3.i
        %tmp.5 = load int ("struct.std::bad_typeid"*)** cast (int (...)** getelementptr ([3 x int (...)*]*  %vtable for Dclass, int 0, long 2) to int
("struct.std::bad_typeid"*)**)          ; <int ("struct.std::bad_typeid"*)*> [#uses=1]
        %tmp.6 = call int %tmp.5( "struct.std::bad_typeid"* %x )                ; <int> [#uses=1]
	ret int %tmp.6
        ret int 0
}

In order words, we now resolve the virtual function call.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@14783 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-07-13 01:49:43 +00:00
parent d9aa7836e2
commit b89e071aea
1 changed files with 32 additions and 20 deletions
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52
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -2947,6 +2947,30 @@ static Constant *GetGEPGlobalInitializer(Constant *C, ConstantExpr *CE) {
return C;
}
static Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI) {
User *CI = cast<User>(LI.getOperand(0));
const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
if (const PointerType *SrcTy =
dyn_cast<PointerType>(CI->getOperand(0)->getType())) {
const Type *SrcPTy = SrcTy->getElementType();
if (SrcPTy->isSized() && DestPTy->isSized() &&
IC.getTargetData().getTypeSize(SrcPTy) ==
IC.getTargetData().getTypeSize(DestPTy) &&
(SrcPTy->isInteger() || isa<PointerType>(SrcPTy)) &&
(DestPTy->isInteger() || isa<PointerType>(DestPTy))) {
// Okay, we are casting from one integer or pointer type to another of
// the same size. Instead of casting the pointer before the load, cast
// the result of the loaded value.
Value *NewLoad = IC.InsertNewInstBefore(new LoadInst(CI->getOperand(0),
CI->getName()), LI);
// Now cast the result of the load.
return new CastInst(NewLoad, LI.getType());
}
}
return 0;
}
Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
Value *Op = LI.getOperand(0);
if (LI.isVolatile()) return 0;
@ -2964,33 +2988,21 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
// Instcombine load (constantexpr_GEP global, 0, ...) into the value loaded...
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op))
if (CE->getOpcode() == Instruction::GetElementPtr)
if (CE->getOpcode() == Instruction::GetElementPtr) {
if (ConstantPointerRef *G=dyn_cast<ConstantPointerRef>(CE->getOperand(0)))
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(G->getValue()))
if (GV->isConstant() && !GV->isExternal())
if (Constant *V = GetGEPGlobalInitializer(GV->getInitializer(), CE))
return ReplaceInstUsesWith(LI, V);
} else if (CE->getOpcode() == Instruction::Cast) {
if (Instruction *Res = InstCombineLoadCast(*this, LI))
return Res;
}
// load (cast X) --> cast (load X) iff safe
if (CastInst *CI = dyn_cast<CastInst>(Op)) {
const Type *DestPTy = cast<PointerType>(CI->getType())->getElementType();
if (const PointerType *SrcTy =
dyn_cast<PointerType>(CI->getOperand(0)->getType())) {
const Type *SrcPTy = SrcTy->getElementType();
if (SrcPTy->isSized() && DestPTy->isSized() &&
TD->getTypeSize(SrcPTy) == TD->getTypeSize(DestPTy) &&
(SrcPTy->isInteger() || isa<PointerType>(SrcPTy)) &&
(DestPTy->isInteger() || isa<PointerType>(DestPTy))) {
// Okay, we are casting from one integer or pointer type to another of
// the same size. Instead of casting the pointer before the load, cast
// the result of the loaded value.
Value *NewLoad = InsertNewInstBefore(new LoadInst(CI->getOperand(0),
CI->getName()), LI);
// Now cast the result of the load.
return new CastInst(NewLoad, LI.getType());
}
}
}
if (CastInst *CI = dyn_cast<CastInst>(Op))
if (Instruction *Res = InstCombineLoadCast(*this, LI))
return Res;
return 0;
}