document why we're not using a straigh `ret`

2015-04-15 02:06:52 -04:00 · 2015-04-15 02:06:52 -04:00 · ae00fa2346
parent d06e7c7cdd
commit ae00fa2346
1 changed files with 2 additions and 0 deletions
--- a/src/swap.s
+++ b/src/swap.s
@ -31,6 +31,8 @@ jmp 2f
  movq %rax, %rsp

  // jump into the new context (return to the call point)
+  // doing this instead of a straight `ret` is 8ns slower,
+  // presumably because the branch predictor tries to be clever about it
  popq %rax
  jmpq *%rax