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2a094bb4d1
Tim Northover remarked that the added patterns for fmls fp16
produce wrong code in case the fsub instruction has a
multiplication as its first operand, i.e., all the patterns FMLSv*_OP1:
> define <8 x half> @test_FMLSv8f16_OP1(<8 x half> %a, <8 x half> %b, <8 x half> %c) {
> ; CHECK-LABEL: test_FMLSv8f16_OP1:
> ; CHECK: fmls {{v[0-9]+}}.8h, {{v[0-9]+}}.8h, {{v[0-9]+}}.8h
> entry:
>
> %mul = fmul fast <8 x half> %c, %b
> %sub = fsub fast <8 x half> %mul, %a
> ret <8 x half> %sub
> }
>
> This doesn't look right to me. The exact instruction produced is "fmls
> v0.8h, v2.8h, v1.8h", which I think calculates "v0 - v2*v1", but the
> IR is calculating "v2*v1-v0". The equivalent <4 x float> code also
> doesn't emit an fmls.
This patch generates an fmla and negates the value of the operand2 of the fsub.
Inspecting the pattern match, I found that there was another mistake in the
opcode to be selected: matching FMULv4*16 should generate FMLSv4*16
and not FMLSv2*32.
Tested on aarch64-linux with make check-all.
Differential Revision: https://reviews.llvm.org/D67990
llvm-svn: 374044
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