CSKY arch has multiple FPU instruction versions such as FPU, FPUv2 and FPUv3 to implement floating operations.
For now, we just only support FPUv2 and FPUv3.
It includes the encoding, asm parsing of instructions and codegen of DAG nodes.
Loading constants inline is expensive on CSKY and it's in general better
to place the constant nearby in code space and then it can be loaded with a
simple 16/32 bit load instruction like lrw.
It needs lift or duplicates constant pool entry to make constant nearby so that lrw instruction can reach.
Lower global symbols such as call/external symbol.
Lower other leaf DAG node such as frame address/block address/jumptable/vastart.
Normally some leaf symbols need reside in constant pool as ABI prefers, and are addressed by
lrw or jsri instructions.
Every symbol in constant pool is lowered with one entry in target constant pool. The
entry has different type corresponding to different leaf node such as blockaddress,
jumptable, or global value.
Complete basic arithmetic operations such as add/sub/mul/div, and it also includes converions
and some specific operations such as bswap.Add load/store patterns to generate different addressing mode instructions.
Also enable some infra such as copy physical register and eliminate frame index.
Ooops. It constructs codegen infra and provide only basic code to generate first add instruction successfully.
Differential Revision: https://reviews.llvm.org/D112206
