Jit64: divwx - Optimize constant dividend

When the dividend is known at compile time, we can eliminate some of the
branching and precompute the result for the overflow case.

Before:
B8 54 D3 E6 02       mov         eax,2E6D354h
85 FF                test        edi,edi
74 0C                je          overflow
3D 00 00 00 80       cmp         eax,80000000h
75 0C                jne         normal_path
83 FF FF             cmp         edi,0FFFFFFFFh
75 07                jne         normal_path
overflow:
C1 F8 1F             sar         eax,1Fh
8B F8                mov         edi,eax
EB 05                jmp         done
normal_path:
99                   cdq
F7 FF                idiv        eax,edi
8B F8                mov         edi,eax
done:

After:
85 FF                test        edi,edi
75 04                jne         normal_path
33 FF                xor         edi,edi
EB 0A                jmp         done
normal_path:
B8 54 D3 E6 02       mov         eax,2E6D354h
99                   cdq
F7 FF                idiv        eax,edi
8B F8                mov         edi,eax
done:

Fairly common with constant dividend of zero. Non-zero values occur
frequently in Ocarina of Time Master Quest.

0 files changed, 0 insertions, 0 deletions