[PATCH] D59739: [WebAssembly] Fix bugs in BLOCK/TRY placement

[Heejin Ahn via Phabricator via llvm-commits]

aheejin created this revision.
aheejin added reviewers: dschuff, sunfish.
Herald added subscribers: llvm-commits, jgravelle-google, sbc100.
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aheejin edited the summary of this revision.
aheejin edited the summary of this revision.

Before we placed all TRY/END_TRY markers before placing BLOCK/END_BLOCK
markers. This couldn't handle this case:

  bb0:
    br bb2
  bb1:          // nearest common dominator of bb3 and bb4
    ...
  bb2:
    br_if ... bb3                                                        
    br bb4
  bb3:
    call @foo   // unwinds to ehpad
  bb4:
    call @bar   // unwinds to ehpad
  ehpad:
    catch
    ...

When we placed TRY markers, we placed it in bb1 because it is the
nearest common dominator of bb3 and bb4. But because bb0 jumps to bb2,
when we placed block markers, we ended up with interleaved scopes like

  block
  try
  end_block
  catch
  end_try

which was not correct.

This patch fixes the bug by placing BLOCK and TRY markers in one pass
while iterating BBs in a function. This also adds some more routines to
`placeTryMarkers`, because we now have to assume that there can be
previously placed BLOCK and END_BLOCK.


Repository:
  rL LLVM

https://reviews.llvm.org/D59739

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

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