[PATCH] newlib: Fix long double for unsupported rounding modes and exceptions

RISC-V newlib fails to build for soft float multilibs since long double
support was enabled in:

  commit 04798b7bb69571452d2cfc7e0b052a9bbd3b619d
  Author: Kito Cheng <[email protected]>
  Date:   Mon Dec 4 15:41:39 2023 +0800

      RISC-V: Support long double math

      Long double for RISC-V is using 128 bit IEEE 754 format like Aarch64,
      so we reference AArch64 to support that.

The RISC-V soft floating point environment only supports the
FE_TONEAREST rounding mode and does not support exceptions.  Guard long
double rounding and exception support with ifdefs based on the presence
of the relevant rounding modes and exceptions.

Tested on gcc/g++ testsuite using RISC-V GNU Newlib Toolchain built by
riscv-gnu-toolchain with multilibs:

    riscv-sim/-march=rv32i/-mabi=ilp32/-mcmodel=medlow
    riscv-sim/-march=rv32iac/-mabi=ilp32/-mcmodel=medlow
    riscv-sim/-march=rv32im/-mabi=ilp32/-mcmodel=medlow
    riscv-sim/-march=rv32imac/-mabi=ilp32/-mcmodel=medlow
    riscv-sim/-march=rv32imafc/-mabi=ilp32f/-mcmodel=medlow
    riscv-sim/-march=rv64imac/-mabi=lp64/-mcmodel=medlow

Co-authored-by: Simon Cook <[email protected]>
---
 newlib/libm/ld/s_fmal.c   | 14 ++++++++++++--
 newlib/libm/ld/s_lrint.c  |  2 ++
 newlib/libm/ld/s_lround.c |  2 ++
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/newlib/libm/ld/s_fmal.c b/newlib/libm/ld/s_fmal.c
index a379346c1..281dd685b 100644
--- a/newlib/libm/ld/s_fmal.c
+++ b/newlib/libm/ld/s_fmal.c
@@ -199,27 +199,37 @@ fmal(long double x, long double y, long double z)
 	 * modes other than FE_TONEAREST are painful.
 	 */
 	if (spread < -LDBL_MANT_DIG) {
+#ifdef FE_INEXACT
 		feraiseexcept(FE_INEXACT);
+#endif
+#ifdef FE_UNDERFLOW
 		if (!isnormal(z))
 			feraiseexcept(FE_UNDERFLOW);
+#endif
 		switch (oround) {
-		case FE_TONEAREST:
+		default: /* FE_TONEAREST */
 			return (z);
+#ifdef FE_TOWARDZERO
 		case FE_TOWARDZERO:
 			if (x > 0.0 ^ y < 0.0 ^ z < 0.0)
 				return (z);
 			else
 				return (nextafterl(z, 0));
+#endif
+#ifdef FE_DOWNWARD
 		case FE_DOWNWARD:
 			if (x > 0.0 ^ y < 0.0)
 				return (z);
 			else
 				return (nextafterl(z, -INFINITY));
-		default:	/* FE_UPWARD */
+#endif
+#ifdef FE_UPWARD
+		case FE_UPWARD:
 			if (x > 0.0 ^ y < 0.0)
 				return (nextafterl(z, INFINITY));
 			else
 				return (z);
+#endif
 		}
 	}
 	if (spread <= LDBL_MANT_DIG * 2)
diff --git a/newlib/libm/ld/s_lrint.c b/newlib/libm/ld/s_lrint.c
index ad9b978fa..dde3cc434 100644
--- a/newlib/libm/ld/s_lrint.c
+++ b/newlib/libm/ld/s_lrint.c
@@ -53,8 +53,10 @@ fn(type x)
 
 	feholdexcept(&env);
 	d = (dtype)roundit(x);
+#if defined(FE_INVALID) && defined(FE_INEXACT)
 	if (fetestexcept(FE_INVALID))
 		feclearexcept(FE_INEXACT);
+#endif
 	feupdateenv(&env);
 	return (d);
 }
diff --git a/newlib/libm/ld/s_lround.c b/newlib/libm/ld/s_lround.c
index f67f9fbeb..fefafa877 100644
--- a/newlib/libm/ld/s_lround.c
+++ b/newlib/libm/ld/s_lround.c
@@ -64,7 +64,9 @@ fn(type x)
 		x = roundit(x);
 		return ((dtype)x);
 	} else {
+#ifdef FE_INVALID
 		feraiseexcept(FE_INVALID);
+#endif
 		return (DTYPE_MAX);
 	}
 }
-- 
2.34.1