For "pat ass", move fake stack to real stack before adjusting SP.

This fixes code that tried to "addi SP, SP, 4" to drop a value that
was in a register, not on the real stack.

Add a rule to optimize "asp 4" (which becomes "loc 4" "ass") when
the value being dropped is already in a GPR.

mach/powerpc/ncg/table

@@ -2005,11 +2005,18 @@ PATTERNS
 		leaving
 			ste ".reghp"
 
+	pat loc ass $1==4                  /* Drop 4 bytes from stack */
+		with exact GPR
+			/* nop */
+		with STACK
+			gen
+				addi SP, SP, {CONST, 4}
+
 	pat ass                            /* Adjust stack by variable amount */
-		with CONST
+		with CONST STACK
 			gen
 				move {SUM_RC, SP, %1.val}, {GPRE, SP}
-		with GPR
+		with GPR STACK
 			gen
 				move {SUM_RR, SP, %1}, {GPRE, SP}