[ARM 1/5 big.LITTLE] Add driver support for rewriting -mcpu names

[James Greenhalgh <james.greenhalgh@arm.com>]

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Hi,

This patch adds machinery to the driver to ensure that big.LITTLE
style tuning names are rewritten before they are passed to the
assembler. This reduces the coupling needed between GCC versions
and assembler versions.

The rule is simple, we truncate the CPU name at the first '.'
character we see.

Thus -mcpu=cortex-a15.cortex-a7 would be truncated to -mcpu=cortex-a15.

Bootstrapped on a ChromeBook and checked for an arm-none-eabi and
an arm-none-linux-gnueabi build.

Thanks,
James

---
gcc/

2013-12-17  James Greenhalgh  <james.greenhalgh@arm.com>

	* common/config/arm/arm-common.c (arm_rewrite_selected_cpu): New.
	(arm_rewrite_mcpu): Likewise.
	* config/arm/arm-protos.h (arm_rewrite_selected_cpu): New.
	* config/arm/arm.h (BIG_LITTLE_SPEC): New.
	(BIG_LITTLE_SPEC_FUNCTIONS): Likewise.
	(EXTRA_SPEC_FUNCTIONS): Include BIG_LITTLE_SPEC_FUNCTIONS.
	(ASM_CPU_SPEC): Include BIG_LITTLE_SPEC.
	* config/arm/arm.c (arm_file_start): Rewrite arm_selecetd_cpu values.

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diff --git a/gcc/common/config/arm/arm-common.c b/gcc/common/config/arm/arm-common.c
index c43a2ce..87f18ec 100644
--- a/gcc/common/config/arm/arm-common.c
+++ b/gcc/common/config/arm/arm-common.c
@@ -63,6 +63,41 @@ arm_except_unwind_info (struct gcc_options *opts)
   return UI_SJLJ;
 }
 
+#define ARM_CPU_NAME_LENGTH 20
+
+/* Truncate NAME at the first '.' character seen, or return
+   NAME unmodified.  */
+
+const char *
+arm_rewrite_selected_cpu (const char *name)
+{
+  static char output_buf[ARM_CPU_NAME_LENGTH + 1] = {0};
+  char *arg_pos;
+
+  strncpy (output_buf, name, ARM_CPU_NAME_LENGTH);
+  arg_pos = strchr (output_buf, '.');
+
+  /* If we found a '.' truncate the entry at that point.  */
+  if (arg_pos)
+    *arg_pos = '\0';
+
+  return output_buf;
+}
+
+/* Called by the driver to rewrite a name passed to the -mcpu
+   argument in preparation to be passed to the assembler.  The
+   name will be in ARGV[0], ARGC should always be 1.  */
+
+const char *
+arm_rewrite_mcpu (int argc, const char **argv)
+{
+  gcc_assert (argc == 1);
+  return arm_rewrite_selected_cpu (argv[0]);
+}
+
+#undef ARM_CPU_NAME_LENGTH
+
+
 #undef  TARGET_DEFAULT_TARGET_FLAGS
 #define TARGET_DEFAULT_TARGET_FLAGS (TARGET_DEFAULT | MASK_SCHED_PROLOG)
 
diff --git a/gcc/config/arm/arm-protos.h b/gcc/config/arm/arm-protos.h
index c5b16da..558f134 100644
--- a/gcc/config/arm/arm-protos.h
+++ b/gcc/config/arm/arm-protos.h
@@ -289,4 +289,7 @@ extern bool arm_autoinc_modes_ok_p (enum machine_mode, enum arm_auto_incmodes);
 
 extern void arm_emit_eabi_attribute (const char *, int, int);
 
+/* Defined in gcc/common/config/arm-common.c.  */
+extern const char *arm_rewrite_selected_cpu (const char *name);
+
 #endif /* ! GCC_ARM_PROTOS_H */
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 7027a26..a4ab6be 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -27527,7 +27527,11 @@ arm_file_start (void)
       else if (strncmp (arm_selected_cpu->name, "generic", 7) == 0)
 	asm_fprintf (asm_out_file, "\t.arch %s\n", arm_selected_cpu->name + 8);
       else
-	asm_fprintf (asm_out_file, "\t.cpu %s\n", arm_selected_cpu->name);
+	{
+	  const char* truncated_name
+	    = arm_rewrite_selected_cpu (arm_selected_cpu->name);
+	  asm_fprintf (asm_out_file, "\t.cpu %s\n", truncated_name);
+	}
 
       if (TARGET_SOFT_FLOAT)
 	{
diff --git a/gcc/config/arm/arm.h b/gcc/config/arm/arm.h
index 8b8b80e..6539ec6 100644
--- a/gcc/config/arm/arm.h
+++ b/gcc/config/arm/arm.h
@@ -2343,16 +2343,25 @@ extern int making_const_table;
    instruction.  */
 #define MAX_LDM_STM_OPS 4
 
+#define BIG_LITTLE_SPEC \
+   " %{mcpu=*:%<mcpu=* -mcpu=%:rewrite_mcpu(%{mcpu=*:%*})}" \
+
+extern const char *arm_rewrite_mcpu (int argc, const char **argv);
+#define BIG_LITTLE_CPU_SPEC_FUNCTIONS \
+  { "rewrite_mcpu", arm_rewrite_mcpu },
+
 #define ASM_CPU_SPEC \
    " %{mcpu=generic-*:-march=%*;"				\
-   "   :%{mcpu=*:-mcpu=%*} %{march=*:-march=%*}}"
+   "   :%{march=*:-march=%*}}"					\
+   BIG_LITTLE_SPEC
 
 /* -mcpu=native handling only makes sense with compiler running on
    an ARM chip.  */
 #if defined(__arm__)
 extern const char *host_detect_local_cpu (int argc, const char **argv);
 # define EXTRA_SPEC_FUNCTIONS						\
-  { "local_cpu_detect", host_detect_local_cpu },
+  { "local_cpu_detect", host_detect_local_cpu },			\
+  BIG_LITTLE_CPU_SPEC_FUNCTIONS
 
 # define MCPU_MTUNE_NATIVE_SPECS					\
    " %{march=native:%<march=native %:local_cpu_detect(arch)}"		\
@@ -2360,6 +2369,7 @@ extern const char *host_detect_local_cpu (int argc, const char **argv);
    " %{mtune=native:%<mtune=native %:local_cpu_detect(tune)}"
 #else
 # define MCPU_MTUNE_NATIVE_SPECS ""
+# define EXTRA_SPEC_FUNCTIONS BIG_LITTLE_CPU_SPEC_FUNCTIONS
 #endif
 
 #define DRIVER_SELF_SPECS MCPU_MTUNE_NATIVE_SPECS