The RISC-V ISA manual was updated on 2018-11-07 (commit 00557c3) to define a
new compressed instruction format, RVC format CA (no actual instruction
encodings were changed). This patch updates the RISC-V backend to define the
new format, and to use it in the relevant instructions.
Differential Revision: https://reviews.llvm.org/D54302
Patch by Luís Marques.
llvm-svn: 347043
Logic to load 32-bit and 64-bit immediates is currently present in
RISCVAsmParser::emitLoadImm in order to support the li pseudoinstruction. With
the introduction of RV64 codegen, there is a greater benefit of sharing
immediate materialisation logic between the MC layer and codegen. The
generateInstSeq helper allows this by producing a vector of simple structs
representing the chosen instructions. This can then be consumed in the MC
layer to produce MCInsts or at instruction selection time to produce
appropriate SelectionDAG node. Sharing this logic means that both the li
pseudoinstruction and codegen can benefit from future optimisations, and
that this logic can be used for materialising constants during RV64 codegen.
This patch does contain a behaviour change: addi will now be produced on RV64
when no lui is necessary to materialise the constant. In that case addiw takes
x0 as the source register, so is semantically identical to addi.
Differential Revision: https://reviews.llvm.org/D52961
llvm-svn: 346937
Alex Bradbury