compiler: emit safepoints in optimized prologs

basis/compiler/cfg/builder/builder.factor

@@ -57,6 +57,7 @@ GENERIC: emit-node ( node -- )
 
 : begin-word ( -- )
     make-kill-block
+    ##safepoint,
     ##prologue,
     ##branch,
     begin-basic-block ;

basis/compiler/cfg/finalization/finalization.factor

@@ -9,7 +9,7 @@ IN: compiler.cfg.finalization
 
 : finalize-cfg ( cfg -- cfg' )
     select-representations
-    schedule-instructions
+    ! schedule-instructions
     insert-gc-checks
     eliminate-write-barriers
     dup compute-uninitialized-sets

basis/cpu/x86/64/64.factor

@@ -60,10 +60,10 @@ M: x86.64 %vm-field-ptr ( dst offset -- )
     [ vm-reg ] dip [+] LEA ;
 
 M: x86.64 %prologue ( n -- )
-    R11 -7 [RIP+] LEA
-    dup PUSH
-    R11 PUSH
-    stack-reg swap 3 cells - SUB ;
+    RAX 0 MOV rc-absolute-cell rel-this
+    stack-reg over cell - SUB
+    stack-reg over 3 cells - [+] RAX MOV
+    stack-reg over 2 cells - [+] swap MOV ;
 
 M: x86.64 %prepare-jump
     pic-tail-reg xt-tail-pic-offset [RIP+] LEA ;