[PATCH] D129593: [InstCombine] Enable strtol folding with nonnull enptr

[Martin Sebor via Phabricator via llvm-commits]

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The `strtol` folding is conditional on the second argument, `endptr`, being a constant null pointer. However, since the idiomatic use case is to pass the function the address of a local `end` pointer as `endptr`, this restriction prevents the folding from taking place in the common case when the pointer is known not to be null.

Not having been able to find a rationale for this decision in D45418 <https://reviews.llvm.org/D45418> (only tests), this change enables the folding also for `endptr` that's known to be nonnull by having the folder store the address of the nul character in `*endptr`.  It stops short of attempting to handle arbitrary pointers since I suspect the cases where nothing is known about the pointer are rare.

Tested on x86_64-linux.

(This patch will need to be rebased on top of D129224 <https://reviews.llvm.org/D129224> once it's committed.)


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D129593

Files:
  llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
  llvm/test/Transforms/InstCombine/str-int-2.ll
  llvm/test/Transforms/InstCombine/str-int.ll

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