[all-commits] [llvm/llvm-project] 109cc5: [DAGCombine] Fold SRA of a load into a narrower si...

[Björn Pettersson via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 109cc5adccaec4c2264c0db3d54bbec1183bf95d
      https://github.com/llvm/llvm-project/commit/109cc5adccaec4c2264c0db3d54bbec1183bf95d
  Author: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
  Date:   2022-01-25 (Tue, 25 Jan 2022)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/PowerPC/pr13891.ll
    M llvm/test/CodeGen/X86/combine-sra-load.ll

  Log Message:
  -----------
  [DAGCombine] Fold SRA of a load into a narrower sign-extending load

An sra is basically sign-extending a narrower value. Fold away the
shift by doing a sextload of a narrower value, when it is legal to
reduce the load width accordingly.

Differential Revision: https://reviews.llvm.org/D116930