[all-commits] [llvm/llvm-project] 508aa6: [WebAssembly] Fix assert in lookup of section symbols

[Wouter van Oortmerssen via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 508aa69e9dbcf4b4de1876cb1b0e9d2c1dbc176f
      https://github.com/llvm/llvm-project/commit/508aa69e9dbcf4b4de1876cb1b0e9d2c1dbc176f
  Author: Wouter van Oortmerssen <aardappel at gmail.com>
  Date:   2021-02-18 (Thu, 18 Feb 2021)

  Changed paths:
    M llvm/lib/MC/MCContext.cpp
    A llvm/test/MC/WebAssembly/section-symbol.s

  Log Message:
  -----------
  [WebAssembly] Fix assert in lookup of section symbols

Fixes assert in: https://bugs.llvm.org/show_bug.cgi?id=49036

getWasmSection creates sections if they don't exist, but doesn't add them to the Symbols table. This may cause problems in subsequent calls to getOrCreateSymbol which checks this table, the calls createSymbol assuming it doesn't exist, which then checks UsedNames and finds out it does exist, causing an assert on trying to rename a non-temp symbol.

I tried also fixing the somewhat unintuitive forced suffixing (adding `0`), but it turns out that WasmObjectWriter currently assumes these section symbols are unique, so that may have to be a separate fix: https://bugs.llvm.org/show_bug.cgi?id=49252

Also worth noting is that getWasmSection calling createSymbol may not be correct to start with, given that createSymbol seems to assume it is creating non-section symbols. But again, for a future fix.

Related: where some of this was introduced: https://github.com/llvm/llvm-project/commit/8d396acac3bc21f688ac707bb42e4698dbdcab7e

Differential Revision: https://reviews.llvm.org/D96473