[all-commits] [llvm/llvm-project] b47267: [WebAssembly] Don't stackify multi-def instruction...

[Alex Crichton via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: b47267441e513f5d65169933cba48c26eb40b803
      https://github.com/llvm/llvm-project/commit/b47267441e513f5d65169933cba48c26eb40b803
  Author: Alex Crichton <alex at alexcrichton.com>
  Date:   2026-06-08 (Mon, 08 Jun 2026)

  Changed paths:
    M llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
    A llvm/test/CodeGen/WebAssembly/multivalue-do-not-stackify.ll
    M llvm/test/CodeGen/WebAssembly/multivalue-stackify.ll
    M llvm/test/CodeGen/WebAssembly/multivalue.ll
    M llvm/test/CodeGen/WebAssembly/multivalue_libcall.ll
    M llvm/test/CodeGen/WebAssembly/wide-arithmetic.ll

  Log Message:
  -----------
  [WebAssembly] Don't stackify multi-def instructions (#200429)

This commit updates the `WebAssemblyRegStackify.cpp` pass to
specifically exclude attempting to stackify the first def of a multi-def
instruction. As the previous comments indicate this is possible to do in
some situations, but the current logic is incomplete and has led to
miscompilations such as #98323 and #199910. One option would be to make
the logic more robust, but in lieu of that in the meantime the change
here is to completely disable stackification in these situations. This
provides at least a "known working" base to build on later and fixes the
known regressions around this.

Closes #98323
Closes #199910



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