[RISC-V][PR target/117649] Fix branch on masked values splitter

Andreas reported GCC mis-compiled GAS for risc-v  Thankfully he also reduced it
to a nice little testcase.

So the whole point of the pattern in question is to "reduce" the constants by
right shifting away common unnecessary bits in RTL expressions like this:

>   [(set (pc)
>         (if_then_else (any_eq
>                     (and:ANYI (match_operand:ANYI 1 "register_operand" "r")
>                           (match_operand 2 "shifted_const_arith_operand" "i"))
>                     (match_operand 3 "shifted_const_arith_operand" "i"))
>          (label_ref (match_operand 0 "" ""))
>          (pc)))

When applicable, the reduced constants in operands 2/3 fit into a simm12 and
thus do not need multi-instruction synthesis.  Note that we have to also shift
operand 1.

That shift should have been an arithmetic shift, but was incorrectly coded as a
logical shift.

Fixed with the obvious change on the right shift opcode.

Expecting to push to the trunk once the pre-commit tester renders its verdict.
I've already tested in this my tester for rv32 and rv64.

	PR target/117649
gcc/
	* config/riscv/riscv.md (branch on masked/shifted operands): Use
	arithmetic rather than logical shift for operand 1.

gcc/testsuite

	* gcc.target/riscv/branch-1.c: Update expected output.
	* gcc.target/riscv/pr117649.c: New test.

gcc/config/riscv/riscv.md

@@ -3153,7 +3153,7 @@
 					     INTVAL (operands[3]))"
   "#"
   "&& reload_completed"
-  [(set (match_dup 4) (lshiftrt:X (match_dup 1) (match_dup 7)))
+  [(set (match_dup 4) (ashiftrt:X (match_dup 1) (match_dup 7)))
    (set (match_dup 4) (and:X (match_dup 4) (match_dup 8)))
    (set (match_dup 5) (match_dup 9))
    (set (pc) (if_then_else (any_eq (match_dup 4) (match_dup 5))

gcc/testsuite/gcc.target/riscv/branch-1.c

@@ -41,7 +41,8 @@ void f6(long long a)
 }
 
 /* { dg-final { scan-assembler-times "slli\t" 2 } } */
-/* { dg-final { scan-assembler-times "srli\t" 5 } } */
+/* { dg-final { scan-assembler-times "srai\t" 2 } } */
+/* { dg-final { scan-assembler-times "srli\t" 3 } } */
 /* { dg-final { scan-assembler-times "andi\t" 3 } } */
 /* { dg-final { scan-assembler-times "\tli\t" 3 } } */
 /* { dg-final { scan-assembler-not "addi\t" } } */

gcc/testsuite/gcc.target/riscv/pr117649.c

@@ -0,0 +1,16 @@
+/* { dg-do run } */
+
+void exit (int);
+
+void __attribute__ ((noinline))
+f (unsigned int i)
+{
+  if ((i & 0xf0000000) != 0xc0000000) __builtin_abort ();
+}
+
+int
+main ()
+{
+  f (0xc0000022);
+  exit (0);
+}