x*rsqrt(x) returns NaN for x == 0, whereas 1/rsqrt(x) returns 0, as
desired.
Verified that the particular nvptx approximate instructions here do in
fact return 0 for x = 0.
llvm-svn: 293713
Summary:
This lets us lower to sqrt.approx and rsqrt.approx under more
circumstances.
* Now we emit sqrt.approx and rsqrt.approx for calls to @llvm.sqrt.f32,
when fast-math is enabled. Previously, we only would emit it for
calls to @llvm.nvvm.sqrt.f. (With this patch we no longer emit
sqrt.approx for calls to @llvm.nvvm.sqrt.f; we rely on intcombine to
simplify llvm.nvvm.sqrt.f into llvm.sqrt.f32.)
* Now we emit the ftz version of rsqrt.approx when ftz is enabled.
Previously, we only emitted rsqrt.approx when ftz was disabled.
Reviewers: hfinkel
Subscribers: llvm-commits, tra, jholewinski
Differential Revision: https://reviews.llvm.org/D28508
llvm-svn: 293605
Previously we'd always lower @llvm.{sin,cos}.f32 to {sin.cos}.approx.f32
instruction even when unsafe FP math was not allowed.
Clang-generated IR is not affected by this as it uses precise sin/cos
from CUDA's libdevice when unsafe math is disabled.
Differential Revision: https://reviews.llvm.org/D28619
llvm-svn: 291936
Summary:
Previously if you had
* a function with the fast-math-enabled attr, followed by
* a function without the fast-math attr,
the second function would inherit the first function's fast-math-ness.
This means that mixing fast-math and non-fast-math functions in a module
was completely broken unless you explicitly annotated every
non-fast-math function with "unsafe-fp-math"="false". This appears to
have been broken since r176986 (March 2013), when the resetTargetOptions
function was introduced.
This patch tests the correct behavior as best we can. I don't think I
can test FPDenormalMode and NoTrappingFPMath, because they aren't used
in any backends during function lowering. Surprisingly, I also can't
find any uses at all of LessPreciseFPMAD affecting generated code.
The NVPTX/fast-math.ll test changes are an expected result of fixing
this bug. When FMA is disabled, we emit add as "add.rn.f32", which
prevents fma combining. Before this patch, fast-math was enabled in all
functions following the one which explicitly enabled it on itself, so we
were emitting plain "add.f32" where we should have generated
"add.rn.f32".
Reviewers: mkuper
Subscribers: hfinkel, majnemer, jholewinski, nemanjai, llvm-commits
Differential Revision: https://reviews.llvm.org/D28507
llvm-svn: 291618
Justin Lebar