display opt, aykm

the arms of the match in regspec_label referenced tables that were not
const. consequently, they would be rebuilt when reached, every time the
match is incanted. this holds through even when regspec_label is
inlined.

each arm could be a const array for a small and easy change, but to
avoid the indirect dispatch on spec.bank i've reorganized register names
into a single const array and selected values for `RegisterBank` such
that indices into that array can be formed.

for my next trick, i may make `REG_NAMES` a `*const u8`, with indices
  picking offsets into the table - 8-byte offsets might do? this should
  compact down size a little more by removing a pointer and size qword
  for each string.

1 files changed, 26 insertions, 48 deletions

diff --git a/src/long_mode/display.rs b/src/long_mode/display.rs
index a4a4d79..42d3683 100644
--- a/src/long_mode/display.rs
+++ b/src/long_mode/display.rs
@@ -115,55 +115,33 @@ impl fmt::Display for Segment {
     }
 }
 
+// register names are grouped by indices scaled by 16.
+// xmm, ymm, zmm all get two indices.
+const REG_NAMES: &[&'static str] = &[
+    "rax", "rcx", "rdx", "rbx", "rsp", "rbp", "rsi", "rdi", "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15",
+    "eax", "ecx", "edx", "ebx", "esp", "ebp", "esi", "edi", "r8d", "r9d", "r10d", "r11d", "r12d", "r13d", "r14d", "r15d",
+    "ax", "cx", "dx", "bx", "sp", "bp", "si", "di", "r8w", "r9w", "r10w", "r11w", "r12w", "r13w", "r14w", "r15w",
+    "al", "cl", "dl", "bl", "ah", "ch", "dh", "bh", "", "", "", "", "", "", "", "",
+    "al", "cl", "dl", "bl", "spl", "bpl", "sil", "dil", "r8b", "r9b", "r10b", "r11b", "r12b", "r13b", "r14b", "r15b",
+    "cr0", "cr1", "cr2", "cr3", "cr4", "cr5", "cr6", "cr7", "cr8", "cr9", "cr10", "cr11", "cr12", "cr13", "cr14", "cr15",
+    "dr0", "dr1", "dr2", "dr3", "dr4", "dr5", "dr6", "dr7", "dr8", "dr9", "dr10", "dr11", "dr12", "dr13", "dr14", "dr15",
+    "cs", "ds", "es", "fs", "gs", "ss", "", "",
+    "xmm0", "xmm1", "xmm2", "xmm3", "xmm4", "xmm5", "xmm6", "xmm7", "xmm8", "xmm9", "xmm10", "xmm11", "xmm12", "xmm13", "xmm14", "xmm15",
+    "xmm0", "xmm1", "xmm2", "xmm3", "xmm4", "xmm5", "xmm6", "xmm7", "xmm8", "xmm9", "xmm10", "xmm11", "xmm12", "xmm13", "xmm14", "xmm15",
+    "ymm0", "ymm1", "ymm2", "ymm3", "ymm4", "ymm5", "ymm6", "ymm7", "ymm8", "ymm9", "ymm10", "ymm11", "ymm12", "ymm13", "ymm14", "ymm15",
+    "ymm0", "ymm1", "ymm2", "ymm3", "ymm4", "ymm5", "ymm6", "ymm7", "ymm8", "ymm9", "ymm10", "ymm11", "ymm12", "ymm13", "ymm14", "ymm15",
+    "zmm0", "zmm1", "zmm2", "zmm3", "zmm4", "zmm5", "zmm6", "zmm7", "zmm8", "zmm9", "zmm10", "zmm11", "zmm12", "zmm13", "zmm14", "zmm15", "zmm16", "zmm17", "zmm18", "zmm19", "zmm20", "zmm21", "zmm22", "zmm23", "zmm24", "zmm25", "zmm26", "zmm27", "zmm28", "zmm29", "zmm30", "zmm31",
+    "st(0)", "st(1)", "st(2)", "st(3)", "st(4)", "st(5)", "st(6)", "st(7)",
+    "mm0", "mm1", "mm2", "mm3", "mm4", "mm5", "mm6", "mm7",
+    "k0", "k1", "k2", "k3", "k4", "k5", "k6", "k7",
+    "eip", "k1", "k2", "k3", "k4", "k5", "k6", "k7",
+    "rip", "k1", "k2", "k3", "k4", "k5", "k6", "k7",
+    "eflags", "k1", "k2", "k3", "k4", "k5", "k6", "k7",
+    "rflags", "k1", "k2", "k3", "k4", "k5", "k6", "k7",
+];
+
 pub(crate) fn regspec_label(spec: &RegSpec) -> &'static str {
-    match spec.bank {
-        RegisterBank::Q => {
-            ["rax", "rcx", "rdx", "rbx", "rsp", "rbp", "rsi", "rdi", "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15"][spec.num as usize]
-        },
-        RegisterBank::D => {
-            ["eax", "ecx", "edx", "ebx", "esp", "ebp", "esi", "edi", "r8d", "r9d", "r10d", "r11d", "r12d", "r13d", "r14d", "r15d"][spec.num as usize]
-        },
-        RegisterBank::W => {
-            ["ax", "cx", "dx", "bx", "sp", "bp", "si", "di", "r8w", "r9w", "r10w", "r11w", "r12w", "r13w", "r14w", "r15w"][spec.num as usize]
-        },
-        RegisterBank::B => {
-            ["al", "cl", "dl", "bl", "ah", "ch", "dh", "bh"][spec.num as usize]
-        },
-        RegisterBank::rB => {
-            ["al", "cl", "dl", "bl", "spl", "bpl", "sil", "dil", "r8b", "r9b", "r10b", "r11b", "r12b", "r13b", "r14b", "r15b"][spec.num as usize]
-        },
-        RegisterBank::EIP => { "eip" },
-        RegisterBank::RIP => { "rip" },
-        RegisterBank::EFlags => { "eflags" },
-        RegisterBank::RFlags => { "rflags" },
-        RegisterBank::CR => {
-            ["cr0", "cr1", "cr2", "cr3", "cr4", "cr5", "cr6", "cr7", "cr8", "cr9", "cr10", "cr11", "cr12", "cr13", "cr14", "cr15"][spec.num as usize]
-        }
-        RegisterBank::DR => {
-            ["dr0", "dr1", "dr2", "dr3", "dr4", "dr5", "dr6", "dr7", "dr8", "dr9", "dr10", "dr11", "dr12", "dr13", "dr14", "dr15"][spec.num as usize]
-        }
-        RegisterBank::X => {
-            ["xmm0", "xmm1", "xmm2", "xmm3", "xmm4", "xmm5", "xmm6", "xmm7", "xmm8", "xmm9", "xmm10", "xmm11", "xmm12", "xmm13", "xmm14", "xmm15"][spec.num as usize]
-        },
-        RegisterBank::Y => {
-            ["ymm0", "ymm1", "ymm2", "ymm3", "ymm4", "ymm5", "ymm6", "ymm7", "ymm8", "ymm9", "ymm10", "ymm11", "ymm12", "ymm13", "ymm14", "ymm15"][spec.num as usize]
-        },
-        RegisterBank::Z => {
-            ["zmm0", "zmm1", "zmm2", "zmm3", "zmm4", "zmm5", "zmm6", "zmm7", "zmm8", "zmm9", "zmm10", "zmm11", "zmm12", "zmm13", "zmm14", "zmm15", "zmm16", "zmm17", "zmm18", "zmm19", "zmm20", "zmm21", "zmm22", "zmm23", "zmm24", "zmm25", "zmm26", "zmm27", "zmm28", "zmm29", "zmm30", "zmm31"][spec.num as usize]
-        },
-        RegisterBank::ST => {
-            ["st(0)", "st(1)", "st(2)", "st(3)", "st(4)", "st(5)", "st(6)", "st(7)"][spec.num as usize]
-        },
-        RegisterBank::MM => {
-            ["mm0", "mm1", "mm2", "mm3", "mm4", "mm5", "mm6", "mm7"][spec.num as usize]
-        }
-        RegisterBank::S => {
-            ["cs", "ds", "es", "fs", "gs", "ss"][spec.num as usize]
-        }
-        RegisterBank::K => {
-            ["k0", "k1", "k2", "k3", "k4", "k5", "k6", "k7"][spec.num as usize]
-        }
-    }
+    unsafe { REG_NAMES.get_unchecked((spec.num as u16 + ((spec.bank as u16) << 3)) as usize) }
 }
 
 impl fmt::Display for RegSpec {