- 0 -> sLit "%rax"; 1 -> sLit "%rbx";
- 2 -> sLit "%rcx"; 3 -> sLit "%rdx";
- 4 -> sLit "%rsi"; 5 -> sLit "%rdi";
- 6 -> sLit "%rbp"; 7 -> sLit "%rsp";
- 8 -> sLit "%r8"; 9 -> sLit "%r9";
- 10 -> sLit "%r10"; 11 -> sLit "%r11";
- 12 -> sLit "%r12"; 13 -> sLit "%r13";
- 14 -> sLit "%r14"; 15 -> sLit "%r15";
- 16 -> sLit "%xmm0"; 17 -> sLit "%xmm1";
- 18 -> sLit "%xmm2"; 19 -> sLit "%xmm3";
- 20 -> sLit "%xmm4"; 21 -> sLit "%xmm5";
- 22 -> sLit "%xmm6"; 23 -> sLit "%xmm7";
- 24 -> sLit "%xmm8"; 25 -> sLit "%xmm9";
- 26 -> sLit "%xmm10"; 27 -> sLit "%xmm11";
- 28 -> sLit "%xmm12"; 29 -> sLit "%xmm13";
- 30 -> sLit "%xmm14"; 31 -> sLit "%xmm15";
- _ -> sLit "very naughty x86_64 register"
+ 0 -> sLit "%rax"; 1 -> sLit "%rbx";
+ 2 -> sLit "%rcx"; 3 -> sLit "%rdx";
+ 4 -> sLit "%rsi"; 5 -> sLit "%rdi";
+ 6 -> sLit "%rbp"; 7 -> sLit "%rsp";
+ 8 -> sLit "%r8"; 9 -> sLit "%r9";
+ 10 -> sLit "%r10"; 11 -> sLit "%r11";
+ 12 -> sLit "%r12"; 13 -> sLit "%r13";
+ 14 -> sLit "%r14"; 15 -> sLit "%r15";
+ _ -> ppr_reg_float i