Optimizer: Be more careful when optimizing away assignments

Checking for SCOPE_SCOPED is too agressive, check for SCOPE_SCOPE_USED
instead.

CHANGES

@@ -91,6 +91,10 @@ o Compiler
   - Fixed some corner cases where file names where missing from
     backtraces.
 
+  - Check the proper flag to determine if a local variable may be used
+    before optimizing away certain assignments if the assignment is
+    immediately followed by a return of the variable in question.
+
 Crypto.ECC
 
   Now works against Nettle 3.5.

src/peep.in

@@ -216,8 +216,8 @@ ASSIGN_GLOBAL_AND_POP GLOBAL_LVALUE($1a) DEC_AND_POP : ADD_NEG_INT(1) ASSIGN_GLO
 GLOBAL_LVALUE INC_AND_POP GLOBAL($1a) : GLOBAL_LVALUE($1a) INC
 GLOBAL_LVALUE DEC_AND_POP GLOBAL($1a) : GLOBAL_LVALUE($1a) DEC
 
-ASSIGN_LOCAL RETURN [!(Pike_compiler->compiler_frame->lexical_scope & SCOPE_SCOPED)]: RETURN
-ASSIGN_LOCAL VOLATILE_RETURN [!(Pike_compiler->compiler_frame->lexical_scope & SCOPE_SCOPED)]: VOLATILE_RETURN
+ASSIGN_LOCAL RETURN [!(Pike_compiler->compiler_frame->lexical_scope & SCOPE_SCOPE_USED)]: RETURN
+ASSIGN_LOCAL VOLATILE_RETURN [!(Pike_compiler->compiler_frame->lexical_scope & SCOPE_SCOPE_USED)]: VOLATILE_RETURN
 
 ASSIGN_LOCAL BRANCH_WHEN_ZERO LOCAL($1a) RETURN LABEL($2a): ASSIGN_LOCAL($1a) RETURN_IF_TRUE LABEL($2a)
 ASSIGN_LOCAL BRANCH_WHEN_ZERO LOCAL($1a) VOLATILE_RETURN LABEL($2a): ASSIGN_LOCAL($1a) RETURN_IF_TRUE LABEL($2a)