X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcompiler%2Fgeneric%2Fvm-ir2tran.lisp;h=420b129139f0d80e7d59f5fcae533613dc1bfbb4;hb=ef0891e470ff35840def7a5717ede18a58266e76;hp=7a0a1ee3369c02c9518ec3aa0ebdbd11249388a6;hpb=f7faed97898dd0e94a18b0d1fca03aaa0fe24ab0;p=sbcl.git

diff --git a/src/compiler/generic/vm-ir2tran.lisp b/src/compiler/generic/vm-ir2tran.lisp
index 7a0a1ee..420b129 100644
--- a/src/compiler/generic/vm-ir2tran.lisp
+++ b/src/compiler/generic/vm-ir2tran.lisp
@@ -14,7 +14,18 @@
            nil)
 
 #!+stack-allocatable-fixed-objects
-(defoptimizer (%make-structure-instance stack-allocate-result) ((&rest args) node dx)
+(defoptimizer (%make-structure-instance stack-allocate-result) ((defstruct-description &rest args) node dx)
+  (aver (constant-lvar-p defstruct-description))
+  ;; A structure instance can be stack-allocated if it has no raw
+  ;; slots, or if we're on a target with a conservatively-scavenged
+  ;; stack.  We have no reader conditional for stack conservation, but
+  ;; it turns out that the only time stack conservation is in play is
+  ;; when we're on GENCGC (since CHENEYGC doesn't have conservation)
+  ;; and C-STACK-IS-CONTROL-STACK (otherwise, the C stack is the
+  ;; number stack, and we precisely-scavenge the control stack).
+  #!-(and :gencgc :c-stack-is-control-stack)
+  (zerop (sb!kernel::dd-raw-length (lvar-value defstruct-description)))
+  #!+(and :gencgc :c-stack-is-control-stack)
   t)
 
 (defoptimizer ir2-convert-reffer ((object) node block name offset lowtag)