[all-commits] [llvm/llvm-project] f678fc: [LegalizeVectorOps] Improve handling of multi-resu...

[topperc via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: f678fc7660b36ce0ad6ce4f05eaa28f3e9fdedb5
      https://github.com/llvm/llvm-project/commit/f678fc7660b36ce0ad6ce4f05eaa28f3e9fdedb5
  Author: Craig Topper <craig.topper at intel.com>
  Date:   2020-01-10 (Fri, 10 Jan 2020)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
    M llvm/test/CodeGen/X86/avx512-cmp.ll

  Log Message:
  -----------
  [LegalizeVectorOps] Improve handling of multi-result operations.

This system wasn't very well designed for multi-result nodes. As
a consequence they weren't consistently registered in the
LegalizedNodes map leading to nodes being revisited for different
results.

I've removed the "Result" variable from the main LegalizeOp method
and used a SDNode* instead. The result number from the incoming
Op SDValue is only used for deciding which result to return to the
caller. When LegalizeOp is called it should always register a
legalized result for all of its results. Future calls for any other
result should be pulled for the LegalizedNodes map.

Legal nodes will now register all of their results in the map
instead of just the one we were called for.

The Expand and Promote handling to use a vector of results similar
to LegalizeDAG. Each of the new results is then re-legalized and
logged in the LegalizedNodes map for all of the Results for the
node being legalized. None of the handles register their own
results now. And none call ReplaceAllUsesOfValueWith now.

Custom handling now always passes result number 0 to LowerOperation.
This matches what LegalizeDAG does. Since the introduction of
STRICT nodes, I've encountered several issues with X86's custom
handling being called with an SDValue pointing at the chain and
our custom handlers using that to get a VT instead of result 0.
This should prevent us from having any more of those issues. On
return we will update the LegalizedNodes map for all results so
we shouldn't call the custom handler again for each result number.

I want to push SDNode* further into the Expand and Promote
handlers, but I've left that for a follow to keep this patch size
down. I've created a dummy SDValue(Node, 0) to keep the handlers
working.

Differential Revision: https://reviews.llvm.org/D72224