master: Remove R/M/W memory operation from alloc-alien-stack-space

The branch "master" has been updated in SBCL:
       via  8b6a050b4664d2c6b8242ae185ac77a81e8b0c06 (commit)
      from  33c68e006d3a0a30df0e6e1007743e2a9e58e6d2 (commit)

- Log -----------------------------------------------------------------
commit 8b6a050b4664d2c6b8242ae185ac77a81e8b0c06
Author: Douglas Katzman <[email protected]>
Date:   Fri Aug 28 18:43:33 2026 -0400

    Remove R/M/W memory operation from alloc-alien-stack-space
    
    Do one more instruction but one fewer memory load, because SUB with a
    memory operand counts as both a load and store.
---
 src/compiler/x86-64/c-call.lisp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/compiler/x86-64/c-call.lisp b/src/compiler/x86-64/c-call.lisp
index 361e41bed..4b1dd7b9f 100644
--- a/src/compiler/x86-64/c-call.lisp
+++ b/src/compiler/x86-64/c-call.lisp
@@ -829,10 +829,10 @@ Floats are passed in integer registers."
     (:result-types system-area-pointer)
     (:generator 0
       (aver (not (location= result rsp-tn)))
+      (inst mov result (alien-stack-ptr))
       (unless (zerop amount)
-        (let ((delta (align-up amount 8)))
-          (inst sub :qword (alien-stack-ptr) delta)))
-      (inst mov result (alien-stack-ptr)))))
+        (inst sub result (align-up amount 8))
+        (inst mov (alien-stack-ptr) result)))))
 
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