[amdgcn] Update lower bounds for the number of registers in non-leaf kernels

Reduce the lower limits on the number of registers requested by non-leaf
kernels to help improve CU occupancy.

2019-11-15  Kwok Cheung Yeung  <kcy@codesourcery.com>

	gcc/
	* config/gcn/gcn.c (MAX_NORMAL_SGPR_COUNT, MAX_NORMAL_VGPR_COUNT): New.
	(gcn_conditional_register_usage): Use constants in place of hard-coded
	values.
	(gcn_hsa_declare_function_name): Set lower bound for number of
	SGPRs/VGPRs in non-leaf kernels to MAX_NORMAL_SGPR_COUNT and
	MAX_NORMAL_VGPR_COUNT.

From-SVN: r278305

gcc/ChangeLog

+2019-11-15  Kwok Cheung Yeung  <kcy@codesourcery.com>
+
+	* config/gcn/gcn.c (MAX_NORMAL_SGPR_COUNT, MAX_NORMAL_VGPR_COUNT): New.
+	(gcn_conditional_register_usage): Use constants in place of hard-coded
+	values.
+	(gcn_hsa_declare_function_name): Set lower bound for number of
+	SGPRs/VGPRs in non-leaf kernels to MAX_NORMAL_SGPR_COUNT and
+	MAX_NORMAL_VGPR_COUNT.
+
 2019-11-15  Martin Jambor  <mjambor@suse.cz>
 
 	* ipa-utils.h (ipa_remove_useless_jump_functions): Remove stray

gcc/config/gcn/gcn.c

@@ -75,6 +75,12 @@ int gcn_isa = 3;		/* Default to GCN3.  */
 
 #define LDS_SIZE 65536
 
+/* The number of registers usable by normal non-kernel functions.
+   The SGPR count includes any special extra registers such as VCC.  */
+
+#define MAX_NORMAL_SGPR_COUNT	64
+#define MAX_NORMAL_VGPR_COUNT	24
+
 /* }}}  */
 /* {{{ Initialization and options.  */
 
@@ -2053,10 +2059,12 @@ gcn_conditional_register_usage (void)
   if (cfun->machine->normal_function)
     {
       /* Restrict the set of SGPRs and VGPRs used by non-kernel functions.  */
-      for (int i = SGPR_REGNO (62); i <= LAST_SGPR_REG; i++)
+      for (int i = SGPR_REGNO (MAX_NORMAL_SGPR_COUNT - 2);
+	   i <= LAST_SGPR_REG; i++)
 	fixed_regs[i] = 1, call_used_regs[i] = 1;
 
-      for (int i = VGPR_REGNO (24); i <= LAST_VGPR_REG; i++)
+      for (int i = VGPR_REGNO (MAX_NORMAL_VGPR_COUNT);
+	   i <= LAST_VGPR_REG; i++)
 	fixed_regs[i] = 1, call_used_regs[i] = 1;
 
       return;
@@ -4908,10 +4916,10 @@ gcn_hsa_declare_function_name (FILE *file, const char *name, tree)
   if (!leaf_function_p ())
     {
       /* We can't know how many registers function calls might use.  */
-      if (vgpr < 64)
-	vgpr = 64;
-      if (sgpr + extra_regs < 102)
-	sgpr = 102 - extra_regs;
+      if (vgpr < MAX_NORMAL_VGPR_COUNT)
+	vgpr = MAX_NORMAL_VGPR_COUNT;
+      if (sgpr + extra_regs < MAX_NORMAL_SGPR_COUNT)
+	sgpr = MAX_NORMAL_SGPR_COUNT - extra_regs;
     }
 
   fputs ("\t.align\t256\n", file);