Commit Graph

5 Commits

Author SHA1 Message Date
Sanjay Patel 1965cc4695 [CodeGen] remove creation of FP cast function attribute
This is the last cleanup step resulting from D115804 .
Now that clang uses intrinsics when we're in the special FP mode,
we don't need a function attribute as an indicator to the backend.
The LLVM part of the change is in D115885.

Differential Revision: https://reviews.llvm.org/D115886
2021-12-19 11:55:00 -05:00
Sanjay Patel 8c7f2a4f87 [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
2021-12-16 09:10:12 -05:00
Fangrui Song e5158b5273 [Driver] Migrate some -f/-fno options to use OptInFFlag and OptOutFFlag 2020-06-04 19:33:14 -07:00
Sanjay Patel c81450e29b [Driver, CodeGen] rename options to disable an FP cast optimization
As suggested in the post-commit thread for rL331056, we should match these 
clang options with the established vocabulary of the corresponding sanitizer
option. Also, the use of 'strict' is well-known for these kinds of knobs, 
and we can improve the descriptive text in the docs.

So this intends to match the logic of D46135 but only change the words.
Matching LLVM commit to match this spelling of the attribute to follow shortly.

Differential Revision: https://reviews.llvm.org/D46236

llvm-svn: 331209
2018-04-30 18:19:03 +00:00
Sanjay Patel d175476566 [Driver, CodeGen] add options to enable/disable an FP cast optimization
As discussed in the post-commit thread for:
rL330437 ( http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20180423/545906.html )

We need a way to opt-out of a float-to-int-to-float cast optimization because too much 
existing code relies on the platform-specific undefined result of those casts when the 
float-to-int overflows.

The LLVM changes associated with adding this function attribute are here:
rL330947
rL330950
rL330951

Also as suggested, I changed the LLVM doc to mention the specific sanitizer flag that 
catches this problem:
rL330958

Differential Revision: https://reviews.llvm.org/D46135

llvm-svn: 331041
2018-04-27 14:22:48 +00:00