srcfile: simplify and make most functions inline

Simplify the srcfile subsystem by making it official that any pointer
passed to src_get() needs to have been obtained from the srcfile
subsystem itself.

Move a lot of the srcfile operations into inline code; often they
amount to a single machine instruction...

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

asm/srcfile.c

@@ -44,8 +44,7 @@
 #include "hashtbl.h"
 #include "srcfile.h"
 
-static const char *file_name = NULL;
+struct src_location _src_here;
-static int32_t line_number = 0;
 
 static struct hash_table filename_hash;
 
@@ -79,45 +78,23 @@ const char *src_set_fname(const char *newname)
         }
     }
 
-    oldname = file_name;
+    oldname = _src_here.filename;
-    file_name = newname;
+    _src_here.filename = newname;
     return oldname;
 }
 
-int32_t src_set_linnum(int32_t newline)
-{
-    int32_t oldline = line_number;
-    line_number = newline;
-    return oldline;
-}
-
 void src_set(int32_t line, const char *fname)
 {
     src_set_fname(fname);
     src_set_linnum(line);
 }
 
-const char *src_get_fname(void)
+struct src_location src_update(struct src_location whence)
 {
-    return file_name;
+    struct src_location oldhere = _src_here;
-}
+
-
+    src_set_fname(whence.filename);
-int32_t src_get_linnum(void)
+    src_set_linnum(whence.lineno);
-{
+
-    return line_number;
+    return oldhere;
-}
-
-int32_t src_get(int32_t *xline, const char **xname)
-{
-    const char *xn = *xname;
-    int32_t xl = *xline;
-
-    *xline = line_number;
-    *xname = file_name;
-
-    /* XXX: Is the strcmp() really needed here? */
-    if (!file_name || !xn || (xn != file_name && strcmp(xn, file_name)))
-        return -2;
-    else
-        return line_number - xl;
 }

asm/srcfile.h

@@ -39,20 +39,64 @@
 
 #include "compiler.h"
 
+struct src_location {
+    const char *filename;
+    int32_t lineno;
+};
+extern struct src_location _src_here;
+
 void src_init(void);
 void src_free(void);
 const char *src_set_fname(const char *newname);
-const char *src_get_fname(void);
+static inline const char *src_get_fname(void)
-int32_t src_set_linnum(int32_t newline);
+{
-int32_t src_get_linnum(void);
+    return _src_here.filename;
+}
+static inline int32_t src_set_linnum(int32_t newline)
+{
+    int32_t oldline = _src_here.lineno;
+    _src_here.lineno = newline;
+    return oldline;
+}
+static inline int32_t src_get_linnum(void)
+{
+    return _src_here.lineno;
+}
 /* Can be used when there is no need for the old information */
 void src_set(int32_t line, const char *filename);
+
 /*
  * src_get gets both the source file name and line.
  * It is also used if you maintain private status about the source location
  * It return 0 if the information was the same as the last time you
  * checked, -2 if the name changed and (new-old) if just the line changed.
+ *
+ * xname must point to a filename string previously returned from any
+ * function of this subsystem or be NULL; another string value will
+ * not work.
  */
-int32_t src_get(int32_t *xline, const char **xname);
+static inline int32_t src_get(int32_t *xline, const char **xname)
+{
+    const char *xn = *xname;
+    int32_t xl = *xline;
+
+    *xline = _src_here.lineno;
+    *xname = _src_here.filename;
+
+    /* The return value is expected to be optimized out almost everywhere */
+    if (!xn || xn != _src_here.filename)
+        return -2;
+    else
+        return _src_here.lineno - xl;
+}
+
+/*
+ * Returns and sets/returns the current information as a structure.
+ */
+static inline struct src_location src_where(void)
+{
+    return _src_here;
+}
+struct src_location src_update(struct src_location);
 
 #endif /* ASM_SRCFILE_H */