[DebugInfo][LoopStrengthReduce] Delete the cmp instruction without salvaging its debug value

[Apochens]

In LSRInstance::OptimizeMax(), the condition of the deleted select instruction is also deleted, but its debug value (which could be salvaged) is not salvaged.

llvm-project/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp

Lines 2559 to 2563 in 3f33e7b

	Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
	Cond->eraseFromParent();
	Sel->eraseFromParent();
	if (Cmp->use_empty())
	Cmp->eraseFromParent();

Here is an example: https://godbolt.org/z/dsvP787zc

[llvmbot]

@llvm/issue-subscribers-debuginfo

Author: Shan Huang (Apochens)

In `LSRInstance::OptimizeMax()`, the condition of the deleted select instruction is also deleted, but its debug value (which could be salvaged) is not salvaged.

llvm-project/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp

Lines 2559 to 2563 in 3f33e7b

	Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
	Cond->eraseFromParent();
	Sel->eraseFromParent();
	if (Cmp->use_empty())
	Cmp->eraseFromParent();

Here is an example: https://godbolt.org/z/dsvP787zc