This reverts commit 737394c4.

The fp-model test was failing on platforms that enable denormal flushing
based on -ffast-math. This needs to reset to IEEE, not the default in
these cases.

Change-Id: Ibbad32f66d0d0b89b9c1173a3a96fb1a570ddd89

This reverts commit c64ca930.

This patch tripped a few build bots:

  http://lab.llvm.org:8011/builders/clang-x86_64-debian-fast/builds/24703/
  http://lab.llvm.org:8011/builders/clang-cmake-x86_64-avx2-linux/builds/13465/
  http://lab.llvm.org:8011/builders/clang-with-lto-ubuntu/builds/15994/

Reverting to clear the bots.

The IR hasn't switched the default yet, so explicitly add the ieee
attributes.

I'm still not really sure how the target default denormal mode should
interact with -fno-unsafe-math-optimizations. The target may have
selected the default mode to be non-IEEE based on the flags or based
on its true behavior, but we don't know which is the case. Since the
only users of a non-IEEE mode without a flag still support IEEE mode,
just reset to IEEE.

Corrected clang amdgpu-features.cl test for 6d614a82 (AMDGPU MFMA built-ins)

Differential Revision: https://reviews.llvm.org/D72723

Currently there are 4 different mechanisms for controlling denormal
flushing behavior, and about as many equivalent frontend controls.

- AMDGPU uses the fp32-denormals and fp64-f16-denormals subtarget features
- NVPTX uses the nvptx-f32ftz attribute
- ARM directly uses the denormal-fp-math attribute
- Other targets indirectly use denormal-fp-math in one DAGCombine
- cl-denorms-are-zero has a corresponding denorms-are-zero attribute

AMDGPU wants a distinct control for f32 flushing from f16/f64, and as
far as I can tell the same is true for NVPTX (based on the attribute
name).

Work on consolidating these into the denormal-fp-math attribute, and a
new type specific denormal-fp-math-f32 variant. Only ARM seems to
support the two different flush modes, so this is overkill for the
other use cases. Ideally we would error on the unsupported
positive-zero mode on other targets from somewhere.

Move the logic for selecting the flush mode into the compiler driver,
instead of handling it in cc1. denormal-fp-math/denormal-fp-math-f32
are now both cc1 flags, but denormal-fp-math-f32 is not yet exposed as
a user flag.

-cl-denorms-are-zero, -fcuda-flush-denormals-to-zero and
-fno-cuda-flush-denormals-to-zero will be mapped to
-fp-denormal-math-f32=ieee or preserve-sign rather than the old
attributes.

Stop emitting the denorms-are-zero attribute for the OpenCL flag. It
has no in-tree users. The meaning would also be target dependent, such
as the AMDGPU choice to treat this as only meaning allow flushing of
f32 and not f16 or f64. The naming is also potentially confusing,
since DAZ in other contexts refers to instructions implicitly treating
input denormals as zero, not necessarily flushing output denormals to
zero.

This also does not attempt to change the behavior for the current
attribute. The LangRef now states that the default is ieee behavior,
but this is inaccurate for the current implementation. The clang
handling is slightly hacky to avoid touching the existing
denormal-fp-math uses. Fixing this will be left for a future patch.

AMDGPU is still using the subtarget feature to control the denormal
mode, but the new attribute are now emitted. A future change will
switch this and remove the subtarget features.

llvm-svn: 371010

Differential Revision: https://reviews.llvm.org/D64430

llvm-svn: 365528

This wasn't setting some of the features from older generations.

llvm-svn: 364123

Differential Revision: https://reviews.llvm.org/D63308

llvm-svn: 363345

Differential Revision: https://reviews.llvm.org/D61875

llvm-svn: 360634

Differential Revision: https://reviews.llvm.org/D60293

llvm-svn: 357792

Differential Revision: https://reviews.llvm.org/D57972

llvm-svn: 353588

Differential Revision: https://reviews.llvm.org/D56525

llvm-svn: 350794

Fast FMAF is not a sufficient condition to enable denormals.
Before VI, enabling denormals caused F32 instructions to
run at F64 speeds.

llvm-svn: 339278

llvm-svn: 339110

llvm-svn: 339109

Changes by
  Matt Arsenault
  Konstantin Zhuravlyov

llvm-svn: 331216