More documentation.

2 files changed, 9 insertions, 9 deletions

diff --git a/README.md b/README.md
index 0369c31..ce41752 100644
--- a/README.md
+++ b/README.md
@@ -68,5 +68,6 @@ Bonus features:
 
 - [intel reference](https://software.intel.com/content/dam/develop/external/us/en/documents-tps/325383-sdm-vol-2abcd.pdf) - Specifically chapter 2.1 and chapter 3.1.
 - [elf spec](https://refspecs.linuxfoundation.org/elf/elf.pdf)
+- [osdev wiki](https://wiki.osdev.org/X86-64_Instruction_Encoding)
 - [goas](https://github.com/DQNEO/goas)
 - [neatas](https://repo.or.cz/neatas.git)
diff --git a/main.c b/main.c
index 9ad714b..212e320 100644
--- a/main.c
+++ b/main.c
@@ -207,15 +207,7 @@ static uint8_t regbits(AsmKind k) { return (k - (ASM_REG_BEGIN + 1)) % 16; }
 
 static uint8_t isreg64(AsmKind k) { return k >= ASM_RAX && k <= ASM_R15; }
 
-/* Register that requires the use of a rex prefix. */
-static uint8_t isrexreg(AsmKind k) {
-  return k > ASM_REG_BEGIN && k < ASM_REG_END &&
-         (regbits(k) & (1 << 3) || k == ASM_SPL || k == ASM_BPL ||
-          k == ASM_SIL || k == ASM_DIL);
-}
-
-/* Compose a rex prefix - See intel manual. */
-
+/* Rex opcode prefix. */
 typedef struct Rex {
   uint8_t required : 1;
   uint8_t w : 1;
@@ -224,6 +216,13 @@ typedef struct Rex {
   uint8_t b : 1;
 } Rex;
 
+/* Register that requires the use of a rex prefix. */
+static uint8_t isrexreg(AsmKind k) {
+  return k > ASM_REG_BEGIN && k < ASM_REG_END &&
+         (regbits(k) & (1 << 3) || k == ASM_SPL || k == ASM_BPL ||
+          k == ASM_SIL || k == ASM_DIL);
+}
+
 static uint8_t rexbyte(Rex rex) {
   return ((1 << 6) | (rex.w << 3) | (rex.r << 2) | (rex.x << 1) | rex.b);
 }