On FMA targets, we can avoid having to load a constant to negate a float/double multiply by instead using a FNMSUB (-(X*Y)-0)
Fix for PR24366
Differential Revision: http://reviews.llvm.org/D14909
llvm-svn: 254495
We currently output FMA instructions on targets which support both FMA4 + FMA (i.e. later Bulldozer CPUS bdver2/bdver3/bdver4).
This patch flips this so FMA4 is preferred; this is for several reasons:
1 - FMA4 is non-destructive reducing the need for mov instructions.
2 - Its more straighforward to commute and fold inputs (although the recent work on FMA has reduced this difference).
3 - All supported targets have FMA4 performance equal or better to FMA - Piledriver (bdver2) in particular has half the throughput when executing FMA instructions.
Its looks like no future AMD processor lines will support FMA4 after the Bulldozer series so we're not causing problems for later CPUs.
Differential Revision: http://reviews.llvm.org/D14997
llvm-svn: 254339
Added FMADD/FMSUB/FNMADD/FNMSUB tests for all types
Added load folding tests for 512-bit vectors
NOTE: Many of the AVX512 FMA instructions don't yet commute/fold correctly
As discussed on D14909
llvm-svn: 254232
autogenerated.
Also update existing test cases which appear to be generated by it and
weren't modified (other than addition of the header) by rerunning it.
llvm-svn: 253917
in-tree implementations of TargetLoweringBase::isFMAFasterThanMulAndAdd in
order to resolve the following issues with fmuladd (i.e. optional FMA)
intrinsics:
1. On X86(-64) targets, ISD::FMA nodes are formed when lowering fmuladd
intrinsics even if the subtarget does not support FMA instructions, leading
to laughably bad code generation in some situations.
2. On AArch64 targets, ISD::FMA nodes are formed for operations on fp128,
resulting in a call to a software fp128 FMA implementation.
3. On PowerPC targets, FMAs are not generated from fmuladd intrinsics on types
like v2f32, v8f32, v4f64, etc., even though they promote, split, scalarize,
etc. to types that support hardware FMAs.
The function has also been slightly renamed for consistency and to force a
merge/build conflict for any out-of-tree target implementing it. To resolve,
see comments and fixed in-tree examples.
llvm-svn: 185956
Simon Pilgrim