llvm dev - Jun 2017 - deleting a range of instructions

Hi,


I am trying to delete a range of instructions ( specified as between [startIns ,
endIns) ) .
the endIns may not be in the same basic block as the start.

I keep getting the following error when trying to delete the last instruction in
-

reference
llvm::ilist_iterator<llvm::ilist_detail::node_options<llvm::Instruction,
true, false, void>, false, false>::operator*() const [OptionsT =
llvm::ilist_detail::node_options<llvm::Instruction, true, false, void>,
IsReverse = false, IsConst = false]: Assertion
`!NodePtr->isKnownSentinel()' failed.


Following is my C++ code -


// delete all instructions between [start,end)
void deleteAllInstructionsInRange(Instruction* startInst,Instruction* endInst)
{
BasicBlock::iterator it(startInst);
BasicBlock::iterator it_end(endInst);
Instruction* currentInst ;
Instruction* lastInst ;

while(it != it_end)
{
currentInst = &*it;
++it;


if (!currentInst->use_empty())
{
currentInst->replaceAllUsesWith(UndefValue::get(currentInst->getType()));
}
currentInst->eraseFromParent();

}
}


Following is my IR -

define i32 @test2() {
entry:
  %calltmp = call i32 @UInt()
  %datasize = alloca i32
  switch i32 %calltmp, label %sw.bb.0 [
    i32 1, label %sw.bb.1
    i32 2, label %sw.bb.2
    i32 3, label %sw.bb.3
  ]
; %res = alloca i8 ------> deleted this
 ; store i8 0, i8* %res  ------> deleted this
  ;%datasize1 = load i32, i32* %datasize  ------> deleted this
  ;ret i32 %datasize1  ------> deleted this
  ret i32 undef ------> Unable to delete this

sw.bb.0:                                          ; preds = %entry
  %resclone0 = alloca i10
  store i10 0, i10* %resclone0
  %datasize1clone0 = load i32, i32* %datasize
  ret i32 %datasize1clone0


Any help will be appreciated.

Thanks.


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