- While SPARC V9 allows tininess to be detected either before or after

  rounding (impl. dep. #55), the SPARC JPS1 responsible for SPARC64 and
  UltraSPARC processors defines that in all cases tinyness is detected
  before rounding, therefore rounding up to the smallest normalised
  number should set the underflow flag.
- If an infinite result is rounded down, the result should have an
  exponent 1 less than the value for infinity.

PR:		144900
Submitted by:	Peter Jeremy
MFC after:	3 days

1 files changed, 10 insertions, 5 deletions

diff --git a/lib/libc/sparc64/fpu/fpu_implode.c b/lib/libc/sparc64/fpu/fpu_implode.c
index 82a8460..2a2a9d0 100644
--- a/lib/libc/sparc64/fpu/fpu_implode.c
+++ b/lib/libc/sparc64/fpu/fpu_implode.c
@@ -329,8 +329,9 @@ __fpu_ftos(fe, fp)
 	 * right to introduce leading zeroes.  Rounding then acts
 	 * differently for normals and subnormals: the largest subnormal
 	 * may round to the smallest normal (1.0 x 2^minexp), or may
-	 * remain subnormal.  In the latter case, signal an underflow
-	 * if the result was inexact or if underflow traps are enabled.
+	 * remain subnormal.  A number that is subnormal before rounding
+	 * will signal an underflow if the result is inexact or if underflow
+	 * traps are enabled.
 	 *
 	 * Rounding a normal, on the other hand, always produces another
 	 * normal (although either way the result might be too big for
@@ -345,8 +346,10 @@ __fpu_ftos(fe, fp)
 	if ((exp = fp->fp_exp + SNG_EXP_BIAS) <= 0) {	/* subnormal */
 		/* -NG for g,r; -SNG_FRACBITS-exp for fraction */
 		(void) __fpu_shr(fp, FP_NMANT - FP_NG - SNG_FRACBITS - exp);
-		if (fpround(fe, fp) && fp->fp_mant[3] == SNG_EXP(1))
+		if (fpround(fe, fp) && fp->fp_mant[3] == SNG_EXP(1)) {
+			fe->fe_cx |= FSR_UF;
 			return (sign | SNG_EXP(1) | 0);
+		}
 		if ((fe->fe_cx & FSR_NX) ||
 		    (fe->fe_fsr & (FSR_UF << FSR_TEM_SHIFT)))
 			fe->fe_cx |= FSR_UF;
@@ -407,6 +410,7 @@ zero:		res[1] = 0;
 	if ((exp = fp->fp_exp + DBL_EXP_BIAS) <= 0) {
 		(void) __fpu_shr(fp, FP_NMANT - FP_NG - DBL_FRACBITS - exp);
 		if (fpround(fe, fp) && fp->fp_mant[2] == DBL_EXP(1)) {
+			fe->fe_cx |= FSR_UF;
 			res[1] = 0;
 			return (sign | DBL_EXP(1) | 0);
 		}
@@ -426,7 +430,7 @@ zero:		res[1] = 0;
 			return (sign | DBL_EXP(DBL_EXP_INFNAN) | 0);
 		}
 		res[1] = ~0;
-		return (sign | DBL_EXP(DBL_EXP_INFNAN) | DBL_MASK);
+		return (sign | DBL_EXP(DBL_EXP_INFNAN - 1) | DBL_MASK);
 	}
 done:
 	res[1] = fp->fp_mant[3];
@@ -468,6 +472,7 @@ zero:		res[1] = res[2] = res[3] = 0;
 	if ((exp = fp->fp_exp + EXT_EXP_BIAS) <= 0) {
 		(void) __fpu_shr(fp, FP_NMANT - FP_NG - EXT_FRACBITS - exp);
 		if (fpround(fe, fp) && fp->fp_mant[0] == EXT_EXP(1)) {
+			fe->fe_cx |= FSR_UF;
 			res[1] = res[2] = res[3] = 0;
 			return (sign | EXT_EXP(1) | 0);
 		}
@@ -487,7 +492,7 @@ zero:		res[1] = res[2] = res[3] = 0;
 			return (sign | EXT_EXP(EXT_EXP_INFNAN) | 0);
 		}
 		res[1] = res[2] = res[3] = ~0;
-		return (sign | EXT_EXP(EXT_EXP_INFNAN) | EXT_MASK);
+		return (sign | EXT_EXP(EXT_EXP_INFNAN - 1) | EXT_MASK);
 	}
 done:
 	res[1] = fp->fp_mant[1];