[PATCH] D50250: [clang][ubsan] Implicit Conversion Sanitizer - integer sign change - clang part

[Roman Lebedev via Phabricator via cfe-commits]

lebedev.ri updated this revision to Diff 159230.
lebedev.ri added a comment.

Do not emit sign-change check in `signed int -> signed char` case.
The truncation check is sufficient:
https://godbolt.org/g/r1wgQG
https://rise4fun.com/Alive/ifj

The middle-end [clearly] does not understand that,
but since the sign-change is completely unneeded here, it's not a blocker.

The `unsigned int -> signed char` case is the only oh-so-special one,
that needs both the truncation and sign change checks,
but the IR can be significantly improved, will handle that:
https://godbolt.org/g/q7e76x
https://rise4fun.com/Alive/2W8


Repository:
  rC Clang

https://reviews.llvm.org/D50250

Files:
  docs/ReleaseNotes.rst
  docs/UndefinedBehaviorSanitizer.rst
  include/clang/Basic/Sanitizers.def
  lib/CodeGen/CGExprScalar.cpp
  test/CodeGen/catch-implicit-integer-conversions-basics.c
  test/CodeGen/catch-implicit-integer-conversions.c
  test/CodeGen/catch-implicit-integer-sign-changes-basics.c
  test/CodeGen/catch-implicit-integer-sign-changes-true-negatives.c
  test/CodeGen/catch-implicit-integer-sign-changes.c
  test/CodeGen/catch-implicit-integer-truncations-basics.c
  test/CodeGen/catch-implicit-integer-truncations.c
  test/CodeGenCXX/catch-implicit-integer-sign-changes-true-negatives.cpp
  test/Driver/fsanitize.c

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