This patch improves on the suggested codegen from PR24475:
https://llvm.org/bugs/show_bug.cgi?id=24475
but only for the fmaxf() case to start, so we can sort out any bugs before
extending to fmin, f64, and vectors.
The fmax / maxnum definitions provide us flexibility for signed zeros, so the
only thing we have to worry about in this replacement sequence is NaN handling.
Note 1: It may be better to implement this as lowerFMAXNUM(), but that exposes
a problem: SelectionDAGBuilder::visitSelect() transforms compare/select
instructions into FMAXNUM nodes if we declare FMAXNUM legal or custom. Perhaps
that should be checking for NaN inputs or global unsafe-math before transforming?
As it stands, that bypasses a big set of optimizations that the x86 backend
already has in PerformSELECTCombine().
Note 2: The v2f32 test reveals another bug; the vector is extended to v4f32, so
we have completely unnecessary operations happening on undef elements of the
vector.
Differential Revision: http://reviews.llvm.org/D15294
llvm-svn: 255700
The 2-element vector case shows a surprising bug: we failed to
eliminate ops on undefs, so there are 4 fmax calls even though
there can only be 2 valid elements in the inputs.
llvm-svn: 254920
Also, switch to x86-64 because once we can lower these to something
more reasonable, there will be less noise in the checks. And add
AVX runs because those will be different than SSE.
llvm-svn: 254879
Sanjay Patel