[all-commits] [llvm/llvm-project] bb0548: [compiler-rt] Avoid signed overflow in floatdidf.c...

[Karl-Johan Karlsson via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: bb0548a6edf0027eca8d92e021c45afd51b29c9e
      https://github.com/llvm/llvm-project/commit/bb0548a6edf0027eca8d92e021c45afd51b29c9e
  Author: Karl-Johan Karlsson <karl-johan.karlsson at ericsson.com>
  Date:   2023-03-17 (Fri, 17 Mar 2023)

  Changed paths:
    M compiler-rt/lib/builtins/floatdidf.c
    M compiler-rt/lib/builtins/floatdisf.c

  Log Message:
  -----------
  [compiler-rt] Avoid signed overflow in floatdidf.c and floatdisf.c

When compiling compiler-rt with -fsanitize=undefined and running testcases you
end up with the following warning:

UBSan: floatdisf.c:27:15: signed integer overflow: 9223372036854775807 - -1 cannot be represented in type 'di_int' (aka 'long long')

This can be avoided by doing the subtraction in a matching unsigned variant of
the type, given that the overflow is the expected result of the subtraction.

The same kind of pattern exists in floatdidf.c

This was found in an out of tree target.

Reviewed By: phosek

Differential Revision: https://reviews.llvm.org/D146135