[PATCH] D19318: [InstCombine][SSE] Demanded vector elements for scalar intrinsics (Part 2)

[Simon Pilgrim via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: majnemer, mkuper, ab, spatel.
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Split from D17490. This patch improves support for determining the demanded vector elements through SSE scalar intrinsics:

1 - demanded vector element support for unary and some extra binary scalar intrinsics (RCP/RSQRT/SQRT/FRCZ and ADD/CMP/DIV/ROUND).
2 - addss/addsd get simplified to a fadd call if we aren't interested in the pass through elements
3 - if we don't need the lowest element of a scalar operation then just use the first argument (the pass through elements) directly

We can add support for propagating demanded elements through any equivalent packed SSE intrinsics in a future patch (these wouldn't use the pass through patterns).

Repository:
  rL LLVM

http://reviews.llvm.org/D19318

Files:
  lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
  test/Transforms/InstCombine/x86-sse.ll
  test/Transforms/InstCombine/x86-sse2.ll
  test/Transforms/InstCombine/x86-sse41.ll
  test/Transforms/InstCombine/x86-xop.ll

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