re PR rtl-optimization/6627 (-fno-align-functions regression from 2.95)

PR optimization/6627
	* toplev.c (force_align_functions_log): New global variable.
	* flags.h (force_align_functions_log): Add extern prototype.
	* varasm.c (assemble_start_function): Use it to force minimum
	function alignment.
	* config/i386/i386.h (FUNCTION_BOUNDARY): Set the correct
	minimum function alignment to one byte.
	(TARGET_PTRMEMFUNC_VBIT_LOCATION): Store the virtual bit in
	the least significant bit of vtable member function pointers.
	* tree.h (enum ptrmemfunc_vbit_where_t): Move definition to
	here from cp/cp-tree.h.

	* cp/cp-tree.h (enum ptrmemfunc_vbit_where_t): Delete definition
	from here, and move it to tree.h.
	* cp/decl.c (cxx_init_decl_processing): If storing the vbit
	in function pointers, ensure that force_align_functions_log
	is atleast one.

	* java/lang.c (java_init): If storing the vbit in function
	pointers, ensure that force_align_functions_log is atleast
	one to aid compatability with g++ vtables.

From-SVN: r57745

gcc/ChangeLog

@@ -1,3 +1,17 @@
+2002-10-02  Roger Sayle  <roger@eyesopen.com>
+
+	PR optimization/6627
+	* toplev.c (force_align_functions_log): New global variable.
+	* flags.h (force_align_functions_log): Add extern prototype.
+	* varasm.c (assemble_start_function): Use it to force minimum
+	function alignment.
+	* config/i386/i386.h (FUNCTION_BOUNDARY): Set the correct
+	minimum function alignment to one byte.
+	(TARGET_PTRMEMFUNC_VBIT_LOCATION): Store the virtual bit in
+	the least significant bit of vtable member function pointers.
+	* tree.h (enum ptrmemfunc_vbit_where_t): Move definition to
+	here from cp/cp-tree.h.
+
 2002-10-02  Matt Austern  <austern@apple.com>
 	* cp/decl.c (walk_vtables_r): Fixed typo that caused result to
 	never get a nonzero value.

gcc/config/i386/i386.h

@@ -695,8 +695,11 @@ extern int x86_prefetch_sse;
 #define FORCE_PREFERRED_STACK_BOUNDARY_IN_MAIN \
   (ix86_preferred_stack_boundary > STACK_BOUNDARY && !TARGET_64BIT)
 
-/* Allocation boundary for the code of a function.  */
-#define FUNCTION_BOUNDARY 16
+/* Minimum allocation boundary for the code of a function.  */
+#define FUNCTION_BOUNDARY 8
+
+/* C++ stores the virtual bit in the lowest bit of function pointers.  */
+#define TARGET_PTRMEMFUNC_VBIT_LOCATION ptrmemfunc_vbit_in_pfn
 
 /* Alignment of field after `int : 0' in a structure.  */
 

gcc/cp/ChangeLog

@@ -1,3 +1,12 @@
+2002-10-02  Roger Sayle  <roger@eyesopen.com>
+
+	PR optimization/6627
+	* cp-tree.h (enum ptrmemfunc_vbit_where_t): Delete definition
+	from here, and move it to tree.h.
+	* decl.c (cxx_init_decl_processing): If storing the vbit
+	in function pointers, ensure that force_align_functions_log
+	is atleast one.
+
 2002-10-01  Mark Mitchell  <mark@codesourcery.com>
 
 	* decl.c (cp_finish_decl): Make sure array types are laid out,

gcc/cp/cp-tree.h

@@ -2540,32 +2540,6 @@ struct lang_decl GTY(())
    member function. [expr.unary.op]/3 */
 #define PTRMEM_OK_P(NODE) TREE_LANG_FLAG_0 (NODE)
 
-/* A pointer-to-function member type looks like:
-
-     struct {
-       __P __pfn;
-       ptrdiff_t __delta;
-     };
-
-   If __pfn is NULL, it is a NULL pointer-to-member-function.
-  
-   (Because the vtable is always the first thing in the object, we
-   don't need its offset.)  If the function is virtual, then PFN is
-   one plus twice the index into the vtable; otherwise, it is just a
-   pointer to the function.
-
-   Unfortunately, using the lowest bit of PFN doesn't work in
-   architectures that don't impose alignment requirements on function
-   addresses, or that use the lowest bit to tell one ISA from another,
-   for example.  For such architectures, we use the lowest bit of
-   DELTA instead of the lowest bit of the PFN, and DELTA will be
-   multiplied by 2.  */
-enum ptrmemfunc_vbit_where_t
-{
-  ptrmemfunc_vbit_in_pfn,
-  ptrmemfunc_vbit_in_delta
-};
-
 /* Get the POINTER_TYPE to the METHOD_TYPE associated with this
    pointer to member function.  TYPE_PTRMEMFUNC_P _must_ be true,
    before using this macro.  */

gcc/cp/decl.c

@@ -6510,6 +6510,12 @@ cxx_init_decl_processing ()
       flag_inline_functions = 0;
     }
 
+  /* Force minimum function alignment if using the least significant
+     bit of function pointers to store the virtual bit.  */
+  if (TARGET_PTRMEMFUNC_VBIT_LOCATION == ptrmemfunc_vbit_in_pfn
+      && force_align_functions_log < 1)
+    force_align_functions_log = 1;
+
   /* Initially, C.  */
   current_lang_name = lang_name_c;
 

gcc/flags.h

@@ -616,6 +616,10 @@ extern int align_labels_max_skip;
 extern int align_functions;
 extern int align_functions_log;
 
+/* Like align_functions_log above, but used by front-ends to force the
+   minimum function alignment.  Zero means no alignment is forced.  */
+extern int force_align_functions_log;
+
 /* Nonzero if we dump in VCG format, not plain text.  */
 extern int dump_for_graph;
 

gcc/java/ChangeLog

@@ -1,3 +1,10 @@
+2002-10-02  Roger Sayle  <roger@eyesopen.com>
+
+	PR optimization/6627
+	* lang.c (java_init): If storing the vbit in function
+	pointers, ensure that force_align_functions_log is atleast
+	one to aid compatability with g++ vtables.
+
 2002-10-01  Nathan Sidwell  <nathan@codesourcery.com>
 
 	* jcf-dump.c (print_constant, case CONSTANT_float): Don't fall

gcc/java/lang.c

@@ -516,6 +516,13 @@ java_init (filename)
   if (flag_inline_functions)
     flag_inline_trees = 1;
 
+  /* Force minimum function alignment if g++ uses the least significant
+     bit of function pointers to store the virtual bit. This is required
+     to keep vtables compatible.  */
+  if (TARGET_PTRMEMFUNC_VBIT_LOCATION == ptrmemfunc_vbit_in_pfn
+      && force_align_functions_log < 1)
+    force_align_functions_log = 1;
+
   /* Open input file.  */
 
   if (filename == 0 || !strcmp (filename, "-"))

gcc/toplev.c

@@ -912,6 +912,10 @@ int align_labels_max_skip;
 int align_functions;
 int align_functions_log;
 
+/* Like align_functions_log above, but used by front-ends to force the
+   minimum function alignment.  Zero means no alignment is forced.  */
+int force_align_functions_log;
+
 /* Table of supported debugging formats.  */
 static const struct
 {

gcc/tree.h

@@ -2114,6 +2114,33 @@ enum tls_model {
 
 extern enum tls_model flag_tls_default;
 
+/* A pointer-to-function member type looks like:
+
+     struct {
+       __P __pfn;
+       ptrdiff_t __delta;
+     };
+
+   If __pfn is NULL, it is a NULL pointer-to-member-function.
+
+   (Because the vtable is always the first thing in the object, we
+   don't need its offset.)  If the function is virtual, then PFN is
+   one plus twice the index into the vtable; otherwise, it is just a
+   pointer to the function.
+
+   Unfortunately, using the lowest bit of PFN doesn't work in
+   architectures that don't impose alignment requirements on function
+   addresses, or that use the lowest bit to tell one ISA from another,
+   for example.  For such architectures, we use the lowest bit of
+   DELTA instead of the lowest bit of the PFN, and DELTA will be
+   multiplied by 2.  */
+
+enum ptrmemfunc_vbit_where_t
+{
+  ptrmemfunc_vbit_in_pfn,
+  ptrmemfunc_vbit_in_delta
+};
+
 #define NULL_TREE (tree) NULL
 
 /* Approximate positive square root of a host double.  This is for

gcc/varasm.c

@@ -1171,6 +1171,8 @@ assemble_start_function (decl, fnname)
 
   /* Tell assembler to move to target machine's alignment for functions.  */
   align = floor_log2 (FUNCTION_BOUNDARY / BITS_PER_UNIT);
+  if (align < force_align_functions_log)
+    align = force_align_functions_log;
   if (align > 0)
     {
       ASM_OUTPUT_ALIGN (asm_out_file, align);