[PATCH] D81758: [WebAssembly] Handle unstackified TEE dest in ExplicitLocals

[Heejin Ahn via Phabricator via llvm-commits]

aheejin created this revision.
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When created in RegStackify pass, TEE has two detinations, where operand
0 is stackified and operand 1 is not. But it is possible that operand 0
is unstackified in fixUnwindMismatches function in CFGStackify pass when
a nested try-catch-end is introduced. In this case, LOCAL_TEE has lost
its purpose, so we generate LOCAL_TEE as planned when op0 remains
stackified, and generate LOCAL_SET instead if op0 got unstackified.

For example,

1. In RegStackify. (r0 is stackified and r1 is not)

  r0, r1 = tee defreg
  ... use r0 ...
  ... use r1 ...



2. In CFGStackify, r0 may get unstackified

3. In ExplicitLocals,

3-a. If r0 remains stackified, use local.tee as planned:

  r0 = local.tee N defreg
  ...
  ... use r0 ... (from stackified r0)
  ...
  local.get N
  ... use r1 ... (from local.get N)

3-b. If r0 got unstackified, use local.set instead:

  local.set N defrag
  ...
  local.get N
  ... use r0 ... (from local.get N)
  local.get N
  ... use r1 ... (from local.get N)


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D81758

Files:
  llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
  llvm/test/CodeGen/WebAssembly/cfg-stackify-eh.ll

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