[amdgcn] Fix handling of VCC_CONDITIONAL_REG

Classify vcc_lo and vcc_hi into the VCC_CONDITIONAL_REG class,
and spill them into SGPRs if necessary.

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

	gcc/
	* config/gcn/gcn.c (gcn_regno_reg_class): Return VCC_CONDITIONAL_REG
	register class for VCC_LO and VCC_HI.
	(gcn_spill_class): Use SGPR_REGS to spill registers in
	VCC_CONDITIONAL_REG.

From-SVN: r278290

gcc/ChangeLog

+2019-11-15  Kwok Cheung Yeung  <kcy@codesourcery.com>
+
+	* config/gcn/gcn.c (gcn_regno_reg_class): Return VCC_CONDITIONAL_REG
+	register class for VCC_LO and VCC_HI.
+	(gcn_spill_class): Use SGPR_REGS to spill registers in
+	VCC_CONDITIONAL_REG.
+
 2019-11-15  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/92324

gcc/config/gcn/gcn.c

@@ -462,6 +462,9 @@ gcn_regno_reg_class (int regno)
     {
     case SCC_REG:
       return SCC_CONDITIONAL_REG;
+    case VCC_LO_REG:
+    case VCC_HI_REG:
+      return VCC_CONDITIONAL_REG;
     case VCCZ_REG:
       return VCCZ_CONDITIONAL_REG;
     case EXECZ_REG:
@@ -629,7 +632,8 @@ gcn_can_split_p (machine_mode, rtx op)
 static reg_class_t
 gcn_spill_class (reg_class_t c, machine_mode /*mode */ )
 {
-  if (reg_classes_intersect_p (ALL_CONDITIONAL_REGS, c))
+  if (reg_classes_intersect_p (ALL_CONDITIONAL_REGS, c)
+      || c == VCC_CONDITIONAL_REG)
     return SGPR_REGS;
   else
     return NO_REGS;