[PATCH] D87361: [SelectionDAG] Add helper guard to automatically insert flags

[Qiu Chaofan via Phabricator via llvm-commits]

qiucf created this revision.
qiucf added reviewers: spatel, nemanjai, aemerson, hfinkel, craig.topper, RKSimon, uweigand, jsji, jonpa, steven.zhang.
Herald added subscribers: llvm-commits, ecnelises, hiraditya.
Herald added a project: LLVM.
qiucf requested review of this revision.

The idea is from review of D87037 <https://reviews.llvm.org/D87037>, @spatel 's comments.

This is like `FastMathFlagGuard` in IR. Since we use SDAG instance to get values, it's with `SelectionDAG`. By creating a `FlagInserter` in current scope, all values created by `getNode` will get the flags, unless explicitly use `Inserter->disable()`.

It's a prototype so in this revision I only enabled in `visitFMA` to show the same flag propagation as D87037 <https://reviews.llvm.org/D87037>.


https://reviews.llvm.org/D87361

Files:
  llvm/include/llvm/CodeGen/SelectionDAG.h
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  llvm/test/CodeGen/PowerPC/fma-combine.ll

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