I am trying to change this
define void @main(float* noalias %arg0, float* noalias %arg1, float*
noalias %arg2) {
entrypoint:
%0 = bitcast float* %arg1 to <4 x float>*
intothis
define void @main(float* noalias %arg0, float* noalias %arg1, float*
noalias %arg2) {
entrypoint:
%0 = getelementptr float* %arg1, i64 0
%1 = bitcast float* %0 to <4 x float>*
I must be close but the final instruction replacement results in a segfault.
for (Instruction& I : BB) {
if (isa<BitCastInst>(I)) {
BitCastInst* BCI = dyn_cast<BitCastInst>(&I);
for (Use& U : I.operands()) {
Value* V = U.get();
if (!dyn_cast<Instruction>(V)) {
// must be a function's argument
std::vector<llvm::Value*> vect_1;
vect_1.push_back(Builder->getInt64(0));
llvm::GetElementPtrInst* gep1 =
llvm::GetElementPtrInst::Create(V, ArrayRef< Value * >(vect_1) );
BB.getInstList().insert(&I, gep1);
llvm::BitCastInst *bci = new BitCastInst (gep1,
BCI->getDestTy() );
llvm::ReplaceInstWithInst( &I , bci );
}
}
}
}
What am I missing?
Thanks,
Frank
On 6/18/15 2:40 PM, Frank Winter wrote:> I am trying to change this > > define void @main(float* noalias %arg0, float* noalias %arg1, float* > noalias %arg2) { > entrypoint: > %0 = bitcast float* %arg1 to <4 x float>* > > intothis > > define void @main(float* noalias %arg0, float* noalias %arg1, float* > noalias %arg2) { > entrypoint: > %0 = getelementptr float* %arg1, i64 0 > %1 = bitcast float* %0 to <4 x float>* > > > I must be close but the final instruction replacement results in a > segfault. > > > for (Instruction& I : BB) {I think the problem might be that the iterator here> if (isa<BitCastInst>(I)) { > BitCastInst* BCI = dyn_cast<BitCastInst>(&I); > for (Use& U : I.operands()) { > Value* V = U.get(); > if (!dyn_cast<Instruction>(V)) { > // must be a function's argument > std::vector<llvm::Value*> vect_1; > vect_1.push_back(Builder->getInt64(0)); > llvm::GetElementPtrInst* gep1 > llvm::GetElementPtrInst::Create(V, ArrayRef< Value * >(vect_1) ); > BB.getInstList().insert(&I, gep1); > > llvm::BitCastInst *bci = new BitCastInst (gep1, > BCI->getDestTy() ); > llvm::ReplaceInstWithInst( &I , bci );is being invalidated here because you're deleting the thing that it points at. You can avoid deleting it if you update the bitcast instruction in place instead. On the plus side, that avoids an unnecessary allocation. Jon> } > } > } > } > > What am I missing? > > Thanks, > Frank > > > > > _______________________________________________ > LLVM Developers mailing list > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev-- Jon Roelofs jonathan at codesourcery.com CodeSourcery / Mentor Embedded
Hi Jon! I guess it makes sense what you say about invalidating "I". I
looked through the LLVM manual but could not find anything about
'replacing in place'. Can I still iterate over the instructions in a
basic block like
for (Instruction& I : BB) {
if (isa<BitCastInst>(I)) {
and change 'I' in place? I said from the plus side.. How's the
pseudo
code for that?
Frank
On 06/18/2015 05:02 PM, Jonathan Roelofs wrote:>
>
> On 6/18/15 2:40 PM, Frank Winter wrote:
>> I am trying to change this
>>
>> define void @main(float* noalias %arg0, float* noalias %arg1, float*
>> noalias %arg2) {
>> entrypoint:
>> %0 = bitcast float* %arg1 to <4 x float>*
>>
>> intothis
>>
>> define void @main(float* noalias %arg0, float* noalias %arg1, float*
>> noalias %arg2) {
>> entrypoint:
>> %0 = getelementptr float* %arg1, i64 0
>> %1 = bitcast float* %0 to <4 x float>*
>>
>>
>> I must be close but the final instruction replacement results in a
>> segfault.
>>
>>
>> for (Instruction& I : BB) {
> I think the problem might be that the iterator here
>> if (isa<BitCastInst>(I)) {
>> BitCastInst* BCI = dyn_cast<BitCastInst>(&I);
>> for (Use& U : I.operands()) {
>> Value* V = U.get();
>> if (!dyn_cast<Instruction>(V)) {
>> // must be a function's argument
>> std::vector<llvm::Value*> vect_1;
>> vect_1.push_back(Builder->getInt64(0));
>> llvm::GetElementPtrInst* gep1 >>
llvm::GetElementPtrInst::Create(V, ArrayRef< Value * >(vect_1) );
>> BB.getInstList().insert(&I, gep1);
>>
>> llvm::BitCastInst *bci = new BitCastInst (gep1,
>> BCI->getDestTy() );
>> llvm::ReplaceInstWithInst( &I , bci );
> is being invalidated here because you're deleting the thing that it
> points at.
>
> You can avoid deleting it if you update the bitcast instruction in
> place instead. On the plus side, that avoids an unnecessary allocation.
>
>
> Jon
>
>> }
>> }
>> }
>> }
>>
>> What am I missing?
>>
>> Thanks,
>> Frank
>>
>>
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
On Thu, Jun 18, 2015 at 1:40 PM, Frank Winter <fwinter at jlab.org> wrote:> I am trying to change this > > define void @main(float* noalias %arg0, float* noalias %arg1, float* noalias > %arg2) { > entrypoint: > %0 = bitcast float* %arg1 to <4 x float>* > > intothis > > define void @main(float* noalias %arg0, float* noalias %arg1, float* noalias > %arg2) { > entrypoint: > %0 = getelementptr float* %arg1, i64 0 > %1 = bitcast float* %0 to <4 x float>* > > > I must be close but the final instruction replacement results in a segfault. > > > for (Instruction& I : BB) { > if (isa<BitCastInst>(I)) { > BitCastInst* BCI = dyn_cast<BitCastInst>(&I); > for (Use& U : I.operands()) { > Value* V = U.get(); > if (!dyn_cast<Instruction>(V)) { > // must be a function's argument > std::vector<llvm::Value*> vect_1; > vect_1.push_back(Builder->getInt64(0)); > llvm::GetElementPtrInst* gep1 > llvm::GetElementPtrInst::Create(V, ArrayRef< Value * >(vect_1) ); > BB.getInstList().insert(&I, gep1); > > llvm::BitCastInst *bci = new BitCastInst (gep1, BCI->getDestTy() > ); > llvm::ReplaceInstWithInst( &I , bci );There is no need to do this. Use U.set(gep1);