[ARM] Implement TARGET_FIXED_CONDITION_CODE_REGS

This patch implements TARGET_FIXED_CONDITION_CODE_REGS on ARM.

We have two main cases to consider: in Thumb1 code there are no
condition code registers, so we simply return false.  For other
cases we set the the first pointer to CC_REGNUM and the second to
VFPCC_REGNUM iff generating hard-float code.

Running the CSiBE benchmark I see a couple of cases (both in the same
file) where this feature kicks in, so it's not a major change.

	* config/arm/arm.c (arm_fixed_condition_code_regs): New function.
	(TARGET_FIXED_CONDITION_CODE_REGS): Redefine.

From-SVN: r250005

gcc/ChangeLog

+2017-07-05  Richard Earnshaw  <rearnsha@arm.com>
+
+	* config/arm/arm.c (arm_fixed_condition_code_regs): New function.
+	(TARGET_FIXED_CONDITION_CODE_REGS): Redefine.
+
 2017-07-05  Richard Sandiford  <richard.sandiford@linaro.org>
 	    Alan Hayward  <alan.hayward@arm.com>
 	    David Sherwood  <david.sherwood@arm.com>

gcc/config/arm/arm.c

@@ -110,6 +110,7 @@ static void arm_print_operand_address (FILE *, machine_mode, rtx);
 static bool arm_print_operand_punct_valid_p (unsigned char code);
 static const char *fp_const_from_val (REAL_VALUE_TYPE *);
 static arm_cc get_arm_condition_code (rtx);
+static bool arm_fixed_condition_code_regs (unsigned int *, unsigned int *);
 static const char *output_multi_immediate (rtx *, const char *, const char *,
 					   int, HOST_WIDE_INT);
 static const char *shift_op (rtx, HOST_WIDE_INT *);
@@ -775,6 +776,9 @@ static const struct attribute_spec arm_attribute_table[] =
 #undef TARGET_CUSTOM_FUNCTION_DESCRIPTORS
 #define TARGET_CUSTOM_FUNCTION_DESCRIPTORS 2
 
+#undef TARGET_FIXED_CONDITION_CODE_REGS
+#define TARGET_FIXED_CONDITION_CODE_REGS arm_fixed_condition_code_regs
+
 
 /* Obstack for minipool constant handling.  */
 static struct obstack minipool_obstack;
@@ -22928,6 +22932,20 @@ get_arm_condition_code (rtx comparison)
   return code;
 }
 
+/* Implement TARGET_FIXED_CONDITION_CODE_REGS.  We only have condition
+   code registers when not targetting Thumb1.  The VFP condition register
+   only exists when generating hard-float code.  */
+static bool
+arm_fixed_condition_code_regs (unsigned int *p1, unsigned int *p2)
+{
+  if (!TARGET_32BIT)
+    return false;
+
+  *p1 = CC_REGNUM;
+  *p2 = TARGET_HARD_FLOAT ? VFPCC_REGNUM : INVALID_REGNUM;
+  return true;
+}
+
 /* Tell arm_asm_output_opcode to output IT blocks for conditionally executed
    instructions.  */
 void