[RISC-V][PR target/118170] Add HF div/sqrt reservation

Clearly an oversight in the generic-ooo model caught by the checking code.  I
should have realized it was generic-ooo as we don't have a pipeline description
for the tenstorrent design yet, just the costing model.

The patch was extracted from the BZ which indicated Anton was the author, so I
kept that.  I'm listed as co-author just in case someone wants to complain
about the testcase in the future.  I didn't do any notable lifting here.

Thanks Peter and Anton!

	PR target/118170
gcc/
	* config/riscv/generic-ooo.md (generic_ooo_float_div_half): New
	reservation.

gcc/testsuite
	* gcc.target/riscv/pr118170.c: New test.

Co-authored-by: Jeff Law <jlaw@ventanamicro.com>

gcc/config/riscv/generic-ooo.md

@@ -145,6 +145,12 @@
   "generic_ooo_issue,generic_ooo_fxu")
 
 ;; Assume float division and sqrt are not pipelined.
+(define_insn_reservation "generic_ooo_float_div_half" 10
+  (and (eq_attr "tune" "generic_ooo")
+       (and (eq_attr "type" "fdiv,fsqrt")
+	    (eq_attr "mode" "HF")))
+  "generic_ooo_issue,generic_ooo_fxu,generic_ooo_div,generic_ooo_div*3")
+
 (define_insn_reservation "generic_ooo_float_div_single" 12
   (and (eq_attr "tune" "generic_ooo")
        (and (eq_attr "type" "fdiv,fsqrt")

gcc/testsuite/gcc.target/riscv/pr118170.c

+/* { dg-do "compile" } */
+/* { dg-options "-O2 -mcpu=tt-ascalon-d8" } */
+_Float16 f;
+
+void
+foo ()
+{
+  f /= 3;
+}