[all-commits] [llvm/llvm-project] 8c7f2a: [CodeGen] use saturating FP casts when compiling w...

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  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 8c7f2a4f871928d8734ee3f03e67d09086850b60
      https://github.com/llvm/llvm-project/commit/8c7f2a4f871928d8734ee3f03e67d09086850b60
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2021-12-16 (Thu, 16 Dec 2021)

  Changed paths:
    M clang/lib/CodeGen/CGExprScalar.cpp
    M clang/test/CodeGen/no-junk-ftrunc.c

  Log Message:
  -----------
  [CodeGen] use saturating FP casts when compiling with "no-strict-float-cast-overflow"

We got an unintended consequence of the optimizer getting smarter when
compiling in a non-standard mode, and there's no good way to inhibit
those optimizations at a later stage. The test is based on an example
linked from D92270.

We allow the "no-strict-float-cast-overflow" exception to normal C
cast rules to preserve legacy code that does not expect overflowing
casts from FP to int to produce UB. See D46236 for details.

Differential Revision: https://reviews.llvm.org/D115804