llvm dev - May 2016 - confused GetElementPtr, how to use it properly.

BasicBlock::iterator bit = BB->begin();

LoadInst *li = = dyn_cast<LoadInst>(bit);

li->dump(); // %tmp6 = load i32* getelementptr inbounds (%struct.node*
@Node, i32 0, i32 0), align 4, !dbg !59

li->getOperand(0)->dump(); // i32* getelementptr inbounds (%struct.node*
@Node, i32 0, i32 0), align 4, !dbg !59

GetElementPtrInst *gep =
dyn_cast<GetElementPtrInst>(li->getOperand(0));

if (gep != NULL) {
std::cout << "gep not NULL" << std::endl;
}

The previous codes' BB is a BasicBlock pointer, I want to get the string
name Node. I want to use dyn_cast to cast

the value of li->getOperand(0) to a GetElementPtr pointer type, but it is
likely can not casted by the dyn_cast operation.

The if statement never executed. How it can be implemented? I confused by
the load instruction? Any advice would be

appreciate, thank you.
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Try casting to GetElementPtrConstantExpr.

Hope that helps,
Diana

http://llvm.org/docs/doxygen/html/classllvm_1_1GetElementPtrConstantExpr.html

On 11 May 2016 at 17:04, PeiLIU via llvm-dev <llvm-dev at lists.llvm.org>
wrote:
> BasicBlock::iterator bit = BB->begin();
>
> LoadInst *li = = dyn_cast<LoadInst>(bit);
>
> li->dump(); // %tmp6 = load i32* getelementptr inbounds (%struct.node*
> @Node, i32 0, i32 0), align 4, !dbg !59
>
> li->getOperand(0)->dump(); // i32* getelementptr inbounds
(%struct.node*
> @Node, i32 0, i32 0), align 4, !dbg !59
>
> GetElementPtrInst *gep =
dyn_cast<GetElementPtrInst>(li->getOperand(0));
>
> if (gep != NULL) {
> std::cout << "gep not NULL" << std::endl;
> }
>
> The previous codes' BB is a BasicBlock pointer, I want to get the
string
> name Node. I want to use dyn_cast to cast
>
> the value of li->getOperand(0) to a GetElementPtr pointer type, but it
is
> likely can not casted by the dyn_cast operation.
>
> The if statement never executed. How it can be implemented? I confused by
> the load instruction? Any advice would be
>
> appreciate, thank you.
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
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>