[PATCH] D79304: [DAG] Fold (mul(abs(x),abs(x))) -> (mul(x,x)) (PR39476)

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: spatel, lebedev.ri, xbolva00, craig.topper.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

This patch adds support for discarding integer absolutes from self-multiplications.

Alive2: http://volta.cs.utah.edu:8080/z/rwcc8W

As part of this I've pulled out various absolute pattern matching code snippets we have and moved them into a MatchABS helper, which returns the source operand on success. We can add other ABS patterns here as required (e.g. PR45691).

NOTE: We shouldn't move the select(0>X,0-X,X) pattern as this is always canonicalized to a branchless pattern in visitVSELECT even if ISD::ABS isn't legal.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D79304

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/X86/combine-mul.ll

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