Fix powerpc round, roundf spurious "inexact" (bug 19238).

The powerpc hard-float round and roundf functions, both 32-bit and
64-bit, raise spurious "inexact" exceptions for integer arguments from
adding 0.5 and rounding to integer toward zero.

Since these functions already save and restore the rounding mode, it's
natural to make them restore the full floating-point state instead to
fix this bug, which this patch does.  The save of the state is moved
after the first floating-point operation on the input so that any
"invalid" exceptions from signaling NaN inputs are properly
preserved.  As a consequence of this approach to the fix, "inexact"
for noninteger arguments (disallowed by TS 18661-1 but not by C99/C11,
see bug 15479) is also avoided for these implementations; this is
*not* a general fix for bug 15479 since plenty of other
implementations of various functions still raise spurious "inexact"
for noninteger arguments.

This issue and fix do not apply to builds using power5+ versions of
round and roundf, which use the frin instruction and avoid "inexact"
exceptions that way.

This patch should get hard-float powerpc32 and powerpc64 (default
function implementations) back to a state where test-float and
test-double will pass after ulps regeneration.

Tested for powerpc32 and powerpc64.

	[BZ #15479]
	[BZ #19238]
	* sysdeps/powerpc/powerpc32/fpu/s_round.S (__round): Save
	floating-point state after first operation on input.  Restore full
	state rather than just rounding mode.
	* sysdeps/powerpc/powerpc32/fpu/s_roundf.S (__roundf): Likewise.
	* sysdeps/powerpc/powerpc64/fpu/s_round.S (__round): Likewise.
	* sysdeps/powerpc/powerpc64/fpu/s_roundf.S (__roundf): Likewise.

2 files changed, 12 insertions, 6 deletions

diff --git a/sysdeps/powerpc/powerpc64/fpu/s_round.S b/sysdeps/powerpc/powerpc64/fpu/s_round.S
index 2f99c04d1f..31ede3953d 100644
--- a/sysdeps/powerpc/powerpc64/fpu/s_round.S
+++ b/sysdeps/powerpc/powerpc64/fpu/s_round.S
@@ -38,11 +38,12 @@
 
 EALIGN (__round, 4, 0)
 	CALL_MCOUNT 0
-	mffs	fp11		/* Save current FPU rounding mode.  */
 	lfd	fp13,.LC0@toc(2)
 	fabs	fp0,fp1
 	fsub	fp12,fp13,fp13	/* generate 0.0  */
 	fcmpu	cr7,fp0,fp13	/* if (fabs(x) > TWO52)  */
+	mffs	fp11		/* Save current FPU rounding mode and
+				   "inexact" state.  */
 	fcmpu	cr6,fp1,fp12	/* if (x > 0.0)  */
 	bnllr-	cr7
 	mtfsfi	7,1		/* Set rounding mode toward 0.  */
@@ -53,7 +54,8 @@ EALIGN (__round, 4, 0)
 	fsub	fp1,fp1,fp13	/* x-= TWO52;  */
 	fabs	fp1,fp1		/* if (x == 0.0)  */
 				/* x = 0.0; */
-	mtfsf	0x01,fp11	/* restore previous rounding mode.  */
+	mtfsf	0xff,fp11	/* Restore previous rounding mode and
+				   "inexact" state.  */
 	blr
 .L4:
 	fsub	fp9,fp1,fp10	/* x+= 0.5;  */
@@ -63,7 +65,8 @@ EALIGN (__round, 4, 0)
 	fnabs	fp1,fp1		/* if (x == 0.0)  */
 				/* x = -0.0; */
 .L9:
-	mtfsf	0x01,fp11	/* restore previous rounding mode.  */
+	mtfsf	0xff,fp11	/* Restore previous rounding mode and
+				   "inexact" state.  */
 	blr
 	END (__round)
 
diff --git a/sysdeps/powerpc/powerpc64/fpu/s_roundf.S b/sysdeps/powerpc/powerpc64/fpu/s_roundf.S
index babb52b0d4..3ccf48c23b 100644
--- a/sysdeps/powerpc/powerpc64/fpu/s_roundf.S
+++ b/sysdeps/powerpc/powerpc64/fpu/s_roundf.S
@@ -39,11 +39,12 @@
 
 EALIGN (__roundf, 4, 0)
 	CALL_MCOUNT 0
-	mffs	fp11		/* Save current FPU rounding mode.  */
 	lfs	fp13,.LC0@toc(2)
 	fabs	fp0,fp1
 	fsubs	fp12,fp13,fp13	/* generate 0.0  */
 	fcmpu	cr7,fp0,fp13	/* if (fabs(x) > TWO23)  */
+	mffs	fp11		/* Save current FPU rounding mode and
+				   "inexact" state.  */
 	fcmpu	cr6,fp1,fp12	/* if (x > 0.0)  */
 	bnllr-	cr7
 	mtfsfi	7,1		/* Set rounding mode toward 0.  */
@@ -54,7 +55,8 @@ EALIGN (__roundf, 4, 0)
 	fsubs	fp1,fp1,fp13	/* x-= TWO23;  */
 	fabs	fp1,fp1		/* if (x == 0.0)  */
 				/* x = 0.0; */
-	mtfsf	0x01,fp11	/* restore previous rounding mode.  */
+	mtfsf	0xff,fp11	/* Restore previous rounding mode and
+				   "inexact" state.  */
 	blr
 .L4:
 	fsubs	fp9,fp1,fp10	/* x+= 0.5;  */
@@ -64,7 +66,8 @@ EALIGN (__roundf, 4, 0)
 	fnabs	fp1,fp1		/* if (x == 0.0)  */
 				/* x = -0.0; */
 .L9:
-	mtfsf	0x01,fp11	/* restore previous rounding mode.  */
+	mtfsf	0xff,fp11	/* Restore previous rounding mode and
+				   "inexact" state.  */
 	blr
 	END (__roundf)