- ;; Save edi and esi register args.
- (inst push edi-tn)
- (inst push esi-tn)
- (inst push ebx-tn)
- ;; Okay, we have pushed the register args. We can trash them
- ;; now.
-
- ;; Initialize src to be end of args.
- (inst lea esi-tn (make-ea :dword :base ebp-tn
- :disp (* sp->fp-offset n-word-bytes)))
- (inst sub esi-tn ebx-tn)
-
- ;; We need to copy from downwards up to avoid overwriting some of
- ;; the yet uncopied args. So we need to use EBX as the copy index
- ;; and ECX as the loop counter, rather than using ECX for both.
- (inst xor ebx-tn ebx-tn)
-
- ;; We used to use REP MOVS here, but on modern x86 it performs
- ;; much worse than an explicit loop for small blocks.
- COPY-LOOP
- (inst mov edi-tn (make-ea :dword :base esi-tn :index ebx-tn))
- ;; The :DISP is to account for the registers saved on the stack
- (inst mov (make-ea :dword :base esp-tn :disp (* 3 n-word-bytes)
- :index ebx-tn)
- edi-tn)
- (inst add ebx-tn n-word-bytes)
- (inst sub ecx-tn n-word-bytes)
- (inst jmp :nz COPY-LOOP)
-
- ;; So now we need to restore EDI and ESI.
- (inst pop ebx-tn)
- (inst pop esi-tn)
- (inst pop edi-tn)
-
+ (let ((delta (* n-word-bytes
+ (- (max 3 (sb-allocated-size 'stack))
+ fixed)))
+ (LOOP (gen-label)))
+ (cond ((zerop delta)
+ ;; nothing to move!
+ )
+ ((minusp delta)
+ ;; stack frame smaller than fixed; moving args to higher
+ ;; addresses (stack grows downard), so copy from the
+ ;; end. Moreover, because we'd have to shrink the frame,
+ ;; esp currently points at the end of the source args.
+ (inst push ebx-tn)
+
+ (emit-label LOOP)
+ (inst sub ecx-tn n-word-bytes)
+ (inst mov ebx-tn (make-ea :dword
+ :base esp-tn :index ecx-tn
+ ;; compensate for PUSH above
+ :disp n-word-bytes))
+ (inst mov (make-ea :dword
+ :base esp-tn :index ecx-tn
+ ;; compensate for PUSH, and
+ ;; add (abs delta)
+ :disp (- n-word-bytes delta))
+ ebx-tn)
+ (inst jmp :nz LOOP)
+
+ (inst pop ebx-tn))
+ ((plusp delta)
+ ;; stack frame larger than fixed. Moving args to lower
+ ;; addresses, so copy from the lowest address. esp
+ ;; already points to the lowest address of the destination.
+ (inst push ebx-tn)
+ (inst push esi-tn)
+
+ (inst xor ebx-tn ebx-tn)
+ (emit-label LOOP)
+ (inst mov esi-tn (make-ea :dword
+ :base esp-tn :index ebx-tn
+ ;; PUSHed 2 words
+ :disp (+ (* 2 n-word-bytes)
+ delta)))
+ (inst mov (make-ea :dword
+ :base esp-tn :index ebx-tn
+ :disp (* 2 n-word-bytes))
+ esi-tn)
+ (inst add ebx-tn n-word-bytes)
+ (inst sub ecx-tn n-word-bytes)
+ (inst jmp :nz LOOP)
+
+ (inst pop esi-tn)
+ (inst pop ebx-tn))))