GitLab

immiediate number. Richards benchmark runs.

[wip] let backend know about exception flow. also add one more test to see if callee-saved register is restored
during catching exception, the test failed (and I marked it as ignored).

liveins

results in different code (the same as clang did)

currently mov constant as imm to a GPR, then mov from GPR
to xmm. A better approach should be put the immediate in memroy,
and load it

1. compiler knows all the registers
2. but only 64bits register is a color (for reg alloc)
3. backend records the length of GPR for each operand during instruction
selection
4. after reg alloc, when replacing temp with a color, find corresponding
GPR for the length recorded before

currently we only use 64bit registers, extend/truncate result if it is
not 64bits. This is awful. Going to use all the registers, for example,
AL, AX, EAX, RAX, but will not use AH (so reg alloc is simpler)

1. grow/shrink frame size in the pro/epilogue. Note: though we removed
push/pop for unused callee saved registers, we still reserve frame space
for them. Because we generate spill on frame before we know exactly how
large a space is. The solution is to make spill locations patchable.
2. control flow will combine branches in switch instruction if they all
target the same destination.

now)

(for callee saved regs, we insert push/pop before reg alloc. and
after allocation, remove unnecessary ones)