llvm-project/llvm/test/Transforms/SafeStack
Vedant Kumar 77ffce6954 [Instruction] Set metadata uses to undef on deletion
Summary:
Replace any extant metadata uses of a dying instruction with undef to
preserve debug info accuracy. Some alternatives include:

- Treat Instruction like any other Value, and point its extant metadata
  uses to an empty ValueAsMetadata node. This makes extant dbg.value uses
  trivially dead (i.e. fair game for deletion in many passes), leading to
  stale dbg.values being in effect for too long.

- Call salvageDebugInfoOrMarkUndef. Not needed to make instruction removal
  correct. OTOH results in wasted work in some common cases (e.g. when all
  instructions in a BasicBlock are deleted).

This came up while discussing some basic cases in
https://reviews.llvm.org/D80052.

Reviewers: jmorse, TWeaver, aprantl, dexonsmith, jdoerfert

Subscribers: jholewinski, qcolombet, hiraditya, jfb, sstefan1, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D80264
2020-05-21 15:58:12 -07:00
..
AArch64
ARM Migrate function attribute "no-frame-pointer-elim" to "frame-pointer"="all" as cleanups after D56351 2019-12-24 15:57:33 -08:00
X86 [Instruction] Set metadata uses to undef on deletion 2020-05-21 15:58:12 -07:00