[Patch,AVR]: Cleanup progmem_section handling.

[Georg-Johann Lay <avr at gjlay dot de>]

progmem_section is a section to put jump tables in.

This patch puts jump tables in individual sections if
-ffunction-section is on and does some more cleanup around
that, i.e. implement TARGET_ASM_FUNCTION_RODATA_SECTION hook.

progmem_section is renamed to progmem_swtable_section and is
local to avr.c now.

What I don't understand is the old restriction that ASM_OUTPUT_ALIGN
only printed .p2align for powers > 1; I changed that to >= 1 so that
jump tables get aligned properly.

Passed without regressions.

Ok to commit?

Johann

	* config/avr/avr.h (progmem_section): Remove Declaration.
	(ASM_OUTPUT_ALIGN): Output .p2align for powers >= 1.
	* config/avr/avr.c (progmem_section): Make static and rename to
	progmem_swtable_section.
	(avr_output_addr_vec_elt): No need to switch sections.
	(avr_asm_init_sections): Use output_section_asm_op as section
	callback for progmem_swtable_section.
	(avr_output_progmem_section_asm_op): Remove Function.
	(TARGET_ASM_FUNCTION_RODATA_SECTION): New Define.
	(avr_asm_function_rodata_section): New static Function.
	* config/avr/elf.h (ASM_OUTPUT_BEFORE_CASE_LABEL): Define to
	output alignment 2**1 for jump tables.

Index: config/avr/elf.h
===================================================================
--- config/avr/elf.h	(revision 178062)
+++ config/avr/elf.h	(working copy)
@@ -37,9 +37,10 @@
 #define ASM_DECLARE_FUNCTION_NAME(FILE, NAME, DECL)     \
   avr_asm_declare_function_name ((FILE), (NAME), (DECL))
 
+/* Output alignment 2**1 for jump tables.  */
 #undef ASM_OUTPUT_BEFORE_CASE_LABEL
 #define ASM_OUTPUT_BEFORE_CASE_LABEL(FILE, PREFIX, NUM, TABLE) \
-  switch_to_section (progmem_section);
+  ASM_OUTPUT_ALIGN ((FILE), 1);
 
 /* Be conservative in crtstuff.c.  */
 #undef INIT_SECTION_ASM_OP
Index: config/avr/avr.c
===================================================================
--- config/avr/avr.c	(revision 178067)
+++ config/avr/avr.c	(working copy)
@@ -113,6 +113,7 @@ static void avr_function_arg_advance (cu
 static bool avr_function_ok_for_sibcall (tree, tree);
 static void avr_asm_named_section (const char *name, unsigned int flags, tree decl);
 static void avr_encode_section_info (tree, rtx, int);
+static section* avr_asm_function_rodata_section (tree);
 
 /* Allocate registers from r25 to r8 for parameters for function calls.  */
 #define FIRST_CUM_REG 26
@@ -135,7 +136,8 @@ const struct base_arch_s *avr_current_ar
 /* Current device.  */
 const struct mcu_type_s *avr_current_device;
 
-section *progmem_section;
+/* Section to put switch tables in.  */
+static GTY(()) section *progmem_swtable_section;
 
 /* To track if code will use .bss and/or .data.  */
 bool avr_need_clear_bss_p = false;
@@ -263,6 +265,8 @@ static const struct attribute_spec avr_a
 #undef TARGET_EXPAND_BUILTIN
 #define TARGET_EXPAND_BUILTIN avr_expand_builtin
 
+#undef TARGET_ASM_FUNCTION_RODATA_SECTION
+#define TARGET_ASM_FUNCTION_RODATA_SECTION avr_asm_function_rodata_section
 
 struct gcc_target targetm = TARGET_INITIALIZER;
 
@@ -5036,18 +5040,6 @@ avr_insert_attributes (tree node, tree *
     }
 }
 
-/* A get_unnamed_section callback for switching to progmem_section.  */
-
-static void
-avr_output_progmem_section_asm_op (const void *arg ATTRIBUTE_UNUSED)
-{
-  fprintf (asm_out_file,
-	   "\t.section .progmem.gcc_sw_table, \"%s\", @progbits\n",
-	   AVR_HAVE_JMP_CALL ? "a" : "ax");
-  /* Should already be aligned, this is just to be safe if it isn't.  */
-  fprintf (asm_out_file, "\t.p2align 1\n");
-}
-
 
 /* Implement `ASM_OUTPUT_ALIGNED_DECL_LOCAL'.  */
 /* Implement `ASM_OUTPUT_ALIGNED_DECL_COMMON'.  */
@@ -5098,9 +5090,23 @@ avr_output_bss_section_asm_op (const voi
 static void
 avr_asm_init_sections (void)
 {
-  progmem_section = get_unnamed_section (AVR_HAVE_JMP_CALL ? 0 : SECTION_CODE,
-					 avr_output_progmem_section_asm_op,
-					 NULL);
+  /* Set up a section for jump tables.  Alignment is handled by
+     ASM_OUTPUT_BEFORE_CASE_LABEL.  */
+  
+  if (AVR_HAVE_JMP_CALL)
+    {
+      progmem_swtable_section
+        = get_unnamed_section (0, output_section_asm_op,
+                               "\t.section\t.progmem.gcc_sw_table"
+                               ",\"a\",@progbits");
+    }
+  else
+    {
+      progmem_swtable_section
+        = get_unnamed_section (SECTION_CODE, output_section_asm_op,
+                               "\t.section\t.progmem.gcc_sw_table"
+                               ",\"ax\",@progbits");
+    }
 
   /* Override section callbacks to keep track of `avr_need_clear_bss_p'
      resp. `avr_need_copy_data_p'.  */
@@ -5111,6 +5117,36 @@ avr_asm_init_sections (void)
 }
 
 
+/* Implement `TARGET_ASM_FUNCTION_RODATA_SECTION'.  */
+
+static section*
+avr_asm_function_rodata_section (tree decl)
+{
+  /* If a function is unused and optimized out by -ffunction-sections and
+     --gc-sections, ensure that the same will happen for its jump tables
+     by putting them into individual sections.  */
+
+  if (decl != NULL_TREE && DECL_SECTION_NAME (decl))
+    {
+      const char *name = TREE_STRING_POINTER (DECL_SECTION_NAME (decl));
+  
+      if (flag_function_sections
+          && STR_PREFIX_P (name, ".text."))
+        {
+          size_t len = strlen (name) + 1;
+          char *rname = (char *) alloca (len + 16);
+          
+          strcat (stpcpy (rname, ".progmem.gcc_sw_table"), name + 5);
+
+          return get_section (rname,
+                              AVR_HAVE_JMP_CALL ? 0 : SECTION_CODE, decl);
+        }
+    }
+        
+  return progmem_swtable_section;
+}
+
+
 /* Implement `TARGET_ASM_NAMED_SECTION'.  */
 /* Track need of __do_clear_bss, __do_copy_data for named sections.  */
 
@@ -6693,7 +6729,6 @@ avr_output_bld (rtx operands[], int bit_
 void
 avr_output_addr_vec_elt (FILE *stream, int value)
 {
-  switch_to_section (progmem_section);
   if (AVR_HAVE_JMP_CALL)
     fprintf (stream, "\t.word gs(.L%d)\n", value);
   else
Index: config/avr/avr.h
===================================================================
--- config/avr/avr.h	(revision 178064)
+++ config/avr/avr.h	(working copy)
@@ -127,10 +127,6 @@ extern const struct base_arch_s avr_arch
 
 #define TARGET_CPU_CPP_BUILTINS()	avr_cpu_cpp_builtins (pfile)
 
-#if !defined(IN_LIBGCC2) && !defined(IN_TARGET_LIBS)
-extern GTY(()) section *progmem_section;
-#endif
-
 #define AVR_HAVE_JMP_CALL (avr_current_arch->have_jmp_call && !TARGET_SHORT_CALLS)
 #define AVR_HAVE_MUL (avr_current_arch->have_mul)
 #define AVR_HAVE_MOVW (avr_current_arch->have_movw_lpmx)
@@ -523,8 +519,8 @@ do {									    \
 
 #define ASM_OUTPUT_ALIGN(STREAM, POWER)			\
   do {							\
-      if ((POWER) > 1)					\
-          fprintf (STREAM, "\t.p2align\t%d\n", POWER);	\
+    if ((POWER) >= 1)					\
+      fprintf (STREAM, "\t.p2align\t%d\n", POWER);	\
   } while (0)
 
 #define CASE_VECTOR_MODE HImode