Sanitize the constant argument for rotr<mode>3

This was dormant for quite some time, but it started happening for me
on gcc.c-torture/compile/pr65153.c sometime after r276645 for -mabi=32 linux runs.

The pattern accepts any SMALL_OPERAND constant value while it asserts during the final
that the value is in the mode size range. I this case it happens that combine_and_move_insns
during ira makes a pattern with negative "shift count" which fails at final stage.

This simple fix just truncates the constant operand to mode size the same as shift patterns.

gcc/ChangeLog:

2019-11-13  Dragan Mladjenovic  <dmladjenovic@wavecomp.com>

	* config/mips/mips.md (rotr<mode>3): Sanitize the constant argument
	instead of asserting its value.

From-SVN: r278152

gcc/ChangeLog

+2019-11-13  Dragan Mladjenovic  <dmladjenovic@wavecomp.com>
+
+	* config/mips/mips.md (rotr<mode>3): Sanitize the constant argument
+	instead of asserting its value.
+
 2019-11-13  Aldy Hernandez  <aldyh@redhat.com>
 
 	* gimple-fold.c (size_must_be_zero_p): Rewrite use of value_range

gcc/config/mips/mips.md

@@ -5845,8 +5845,8 @@
   "ISA_HAS_ROR"
 {
   if (CONST_INT_P (operands[2]))
-    gcc_assert (INTVAL (operands[2]) >= 0
-		&& INTVAL (operands[2]) < GET_MODE_BITSIZE (<MODE>mode));
+    operands[2] = GEN_INT (INTVAL (operands[2])
+                           & (GET_MODE_BITSIZE (<MODE>mode) - 1));
 
   return "<d>ror\t%0,%1,%2";
 }