1 files changed, 11 insertions, 8 deletions
diff --git a/quine.asm b/quine.asm
index 3136a11..157e87b 100644
--- a/quine.asm
+++ b/quine.asm
@@ -471,10 +471,9 @@ end macro
 ; Take a 64-bit source register, store its value into the address pointed to
 ; by a 64-bit target register.
 ;
-; For rbp, the only modes available also have displacement; we use an 8-bit
-; one and set it to zero. The other registers could be encoded without the
-; displacement, but for simplicity's sake we do the same thing for all of
-; them.
+; For a target of rbp, the only modes available also have displacement; we
+; disallow that. Use mov.disp8.qreg.qreg for that case, and set a displacement
+; of 0.
 ;
 ; In understanding this, pay close attention to the Op/En column in the opcode
 ; table. The "MR" variant means the ModRM byte's reg field (the middle one)
@@ -495,17 +494,19 @@ end macro
 ; is for whichever register is specified in the R/M field. Sometimes that's
 ; the source, and sometimes it's the target, depending on the opcode.
 macro mov.indirect.qreg.qreg target, source
+  match =rbp, target
+    assert 0
+  end match
   qwordreg sreg, source
   qwordreg treg, target
   rex.w
   db 0x89
-  modrm 1, sreg, treg
+  modrm 0, sreg, treg
   match =rsp, target
     ; R/M = rsp is the SIB case
     sib 0, 4, treg
       ; no scaling, no indexing, target as base
   end match
-  db 0
 end macro
 
 
@@ -1038,7 +1039,7 @@ end macro
 ;
 ; We need to treat a target of rsp specially because it's the SIB case per
 ; table 2-2.
-macro mov.disp8.qreg.qreg target, offset, source
+macro mov.disp8.qreg.qreg offset, target, source
   qwordreg sreg, source
   qwordreg treg, target
   rex.w
@@ -1723,7 +1724,7 @@ end macro
 ;;;
 macro pushcontrol source
   lea.qreg.disp8.qreg rbp, -8, rbp
-  mov.indirect.qreg.qreg rbp, source
+  mov.disp8.qreg.qreg 0, rbp, source
 end macro
 
 macro popcontrol target
@@ -7229,7 +7230,9 @@ defword addressing_indirect_reg64, 0
   dq dup, rbp, ne, zbranch, 23*8
   ; Check whether the R/M register is rsp; save the test result for later.
   dq dup, rsp, eq, lit, 4, unroll
+  ; (equality result, output point, reg/op value, reg/mem name)
   dq reg64, lit, 0, unroll3, modrm
+  ; (equality result, output point)
   ; If the R/M register was rsp, we need an SIB byte; otherwise, skip it.
   dq swap, zbranch, 8*8, lit, 0, lit, 4, rsp, reg64, sib
   dq exit