[PATCH] RISC-V: Fix -fsignaling-nans for glibc testsuite.

[Jim Wilson <jimw at sifive dot com>]

This makes -fsignaling-nans work correctly, fixing 20 glibc testsuite failures.
The FP quiet compare pattern is ignoring all exceptions, including for SNaNs.
To make this work right when -fsignaling-nan, we need an extra eq compare to
raise an exception, but only when HONOR_SNANS is true.  So we get the more
efficient code in the default case, and code that works for the glibc
testsuite when -fsignaling-nans is used.

This was tested with cross riscv32-elf and riscv64-linux builds and checks.
It was also tested with a riscv64-linux glibc build and check

	gcc/
	* config/riscv/riscv.md (f<quiet_pattern>_quiet<ANYF:mode><X:mode>4):
	Add define_expand.  Add ! HONOR_SNANS check to current pattern.  Add
	new pattern using HONOR_SNANS that emits one extra instruction.
---
 gcc/config/riscv/riscv.md | 34 ++++++++++++++++++++++++++++------
 1 file changed, 28 insertions(+), 6 deletions(-)

diff --git a/gcc/config/riscv/riscv.md b/gcc/config/riscv/riscv.md
index 4162dc578e8..b6c20230ffd 100644
--- a/gcc/config/riscv/riscv.md
+++ b/gcc/config/riscv/riscv.md
@@ -1957,19 +1957,41 @@
   [(set_attr "type" "fcmp")
    (set_attr "mode" "<UNITMODE>")])
 
-(define_insn "f<quiet_pattern>_quiet<ANYF:mode><X:mode>4"
-   [(set (match_operand:X         0 "register_operand" "=r")
+(define_expand "f<quiet_pattern>_quiet<ANYF:mode><X:mode>4"
+   [(parallel [(set (match_operand:X      0 "register_operand")
+		    (unspec:X
+		     [(match_operand:ANYF 1 "register_operand")
+		      (match_operand:ANYF 2 "register_operand")]
+		     QUIET_COMPARISON))
+	       (clobber (match_scratch:X 3))])]
+  "TARGET_HARD_FLOAT")
+
+(define_insn "*f<quiet_pattern>_quiet<ANYF:mode><X:mode>4_default"
+   [(set (match_operand:X      0 "register_operand" "=r")
 	 (unspec:X
-	     [(match_operand:ANYF 1 "register_operand" " f")
-	      (match_operand:ANYF 2 "register_operand" " f")]
-	     QUIET_COMPARISON))
+	  [(match_operand:ANYF 1 "register_operand" " f")
+	   (match_operand:ANYF 2 "register_operand" " f")]
+	  QUIET_COMPARISON))
     (clobber (match_scratch:X 3 "=&r"))]
-  "TARGET_HARD_FLOAT"
+  "TARGET_HARD_FLOAT && ! HONOR_SNANS (<ANYF:MODE>mode)"
   "frflags\t%3\n\tf<quiet_pattern>.<fmt>\t%0,%1,%2\n\tfsflags %3"
   [(set_attr "type" "fcmp")
    (set_attr "mode" "<UNITMODE>")
    (set (attr "length") (const_int 12))])
 
+(define_insn "*f<quiet_pattern>_quiet<ANYF:mode><X:mode>4_snan"
+   [(set (match_operand:X      0 "register_operand" "=r")
+	 (unspec:X
+	  [(match_operand:ANYF 1 "register_operand" " f")
+	   (match_operand:ANYF 2 "register_operand" " f")]
+	  QUIET_COMPARISON))
+    (clobber (match_scratch:X 3 "=&r"))]
+  "TARGET_HARD_FLOAT && HONOR_SNANS (<ANYF:MODE>mode)"
+  "frflags\t%3\n\tf<quiet_pattern>.<fmt>\t%0,%1,%2\n\tfsflags %3\n\tfeq.<fmt>\tzero,%1,%2"
+  [(set_attr "type" "fcmp")
+   (set_attr "mode" "<UNITMODE>")
+   (set (attr "length") (const_int 16))])
+
 (define_insn "*seq_zero_<X:mode><GPR:mode>"
   [(set (match_operand:GPR       0 "register_operand" "=r")
 	(eq:GPR (match_operand:X 1 "register_operand" " r")
-- 
2.17.1