Sjoerd Meijer 77cd5c40d2 [ARM] Armv8.2-A FP16 code generation (part 1/3) ... This is the groundwork for Armv8.2-A FP16 code generation . Clang passes and returns _Float16 values as floats, together with the required bitconverts and truncs etc. to implement correct AAPCS behaviour, see D42318. We will implement half-precision argument passing/returning lowering in the ARM backend soon, but for now this means that this: _Float16 sub(_Float16 a, _Float16 b) { return a + b; } gets lowered to this: define float @sub(float %a.coerce, float %b.coerce) { entry: %0 = bitcast float %a.coerce to i32 %tmp.0.extract.trunc = trunc i32 %0 to i16 %1 = bitcast i16 %tmp.0.extract.trunc to half <SNIP> %add = fadd half %1, %3 <SNIP> } When FullFP16 is *not* supported, we don't make f16 a legal type, and we get legalization for "free", i.e. nothing changes and everything works as before. And also f16 argument passing/returning is handled. When FullFP16 is supported, we do make f16 a legal type, and have 2 places that we need to patch up: f16 argument passing and returning, which involves minor tweaks to avoid unnecessary code generation for some bitcasts. As a "demonstrator" that this works for the different FP16, FullFP16, softfp modes, etc., I've added match rules to the VSUB instruction description showing that we can codegen this instruction from IR, but more importantly, also to some conversion instructions. These conversions were causing issue before in the FP16 and FullFP16 cases. I've also added match rules to the VLDRH and VSTRH desriptions, so that we can actually compile the entire half-precision sub code example above. This showed that these loads and stores had the wrong addressing mode specified: AddrMode5 instead of AddrMode5FP16, which turned out not be implemented at all, so that has also been added. This is the minimal patch that shows all the different moving parts. In patch 2/3 I will add some efficient lowering of bitcasts, and in 2/3 I will add the remaining Armv8.2-A FP16 instruction descriptions. Thanks to Sam Parker and Oliver Stannard for their help and reviews! Differential Revision: https://reviews.llvm.org/D38315 llvm-svn: 323512		2018-01-26 09:26:40 +00:00
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ARMDisassembler.cpp	[ARM] Armv8.2-A FP16 code generation (part 1/3)	2018-01-26 09:26:40 +00:00
CMakeLists.txt
LLVMBuild.txt