PowerPC: Fix nearbyint/nearbyintf result for FE_DOWNWARD

This patch fixes the powerpc32 optimized nearbyint/nearbyintf bogus
results for FE_DOWNWARD rounding mode.  This is due wrong instructions
sequence used in the rounding calculation (two subtractions instead of
adition and a subtraction).

Fixes BZ#16815.

3 files changed, 203 insertions, 10 deletions

diff --git a/sysdeps/powerpc/fpu/libm-test-ulps b/sysdeps/powerpc/fpu/libm-test-ulps
index 27f228c..3319233 100644
--- a/sysdeps/powerpc/fpu/libm-test-ulps
+++ b/sysdeps/powerpc/fpu/libm-test-ulps
@@ -452,6 +452,54 @@ ifloat: 1
 ildouble: 1
 ldouble: 1
 
+Function: Real part of "catan_downward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 5
+ldouble: 5
+
+Function: Imaginary part of "catan_downward":
+double: 2
+float: 2
+idouble: 2
+ifloat: 2
+ildouble: 6
+ldouble: 6
+
+Function: Real part of "catan_towardzero":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 6
+ldouble: 6
+
+Function: Imaginary part of "catan_towardzero":
+double: 2
+float: 1
+idouble: 2
+ifloat: 1
+ildouble: 2
+ldouble: 2
+
+Function: Real part of "catan_upward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 3
+ldouble: 3
+
+Function: Imaginary part of "catan_upward":
+double: 3
+float: 3
+idouble: 3
+ifloat: 3
+ildouble: 5
+ldouble: 5
+
 Function: Real part of "catanh":
 double: 4
 float: 1
@@ -466,6 +514,54 @@ ifloat: 1
 ildouble: 1
 ldouble: 1
 
+Function: Real part of "catanh_downward":
+double: 2
+float: 2
+idouble: 2
+ifloat: 2
+ildouble: 3
+ldouble: 3
+
+Function: Imaginary part of "catanh_downward":
+double: 1
+float: 2
+idouble: 1
+ifloat: 2
+ildouble: 5
+ldouble: 5
+
+Function: Real part of "catanh_towardzero":
+double: 2
+float: 1
+idouble: 2
+ifloat: 1
+ildouble: 2
+ldouble: 2
+
+Function: Imaginary part of "catanh_towardzero":
+double: 1
+float: 2
+idouble: 1
+ifloat: 2
+ildouble: 6
+ldouble: 6
+
+Function: Real part of "catanh_upward":
+double: 4
+float: 3
+idouble: 4
+ifloat: 3
+ildouble: 8
+ldouble: 8
+
+Function: Imaginary part of "catanh_upward":
+double: 1
+float: 1
+idouble: 1
+ifloat: 1
+ildouble: 3
+ldouble: 3
+
 Function: "cbrt":
 double: 1
 float: 1
@@ -672,6 +768,102 @@ ifloat: 1
 ildouble: 2
 ldouble: 2
 
+Function: Real part of "clog10_downward":
+double: 3
+float: 3
+idouble: 3
+ifloat: 3
+ildouble: 7
+ldouble: 7
+
+Function: Imaginary part of "clog10_downward":
+double: 3
+float: 2
+idouble: 3
+ifloat: 2
+ildouble: 7
+ldouble: 7
+
+Function: Real part of "clog10_towardzero":
+double: 3
+float: 2
+idouble: 3
+ifloat: 2
+ildouble: 8
+ldouble: 8
+
+Function: Imaginary part of "clog10_towardzero":
+double: 3
+float: 2
+idouble: 3
+ifloat: 2
+ildouble: 7
+ldouble: 7
+
+Function: Real part of "clog10_upward":
+double: 4
+float: 3
+idouble: 4
+ifloat: 3
+ildouble: 8
+ldouble: 8
+
+Function: Imaginary part of "clog10_upward":
+double: 2
+float: 2
+idouble: 2
+ifloat: 2
+ildouble: 6
+ldouble: 6
+
+Function: Real part of "clog_downward":
+double: 2
+float: 2
+idouble: 2
+ifloat: 2
+ildouble: 3
+ldouble: 3
+
+Function: Imaginary part of "clog_downward":
+double: 1
+float: 2
+idouble: 1
+ifloat: 2
+ildouble: 3
+ldouble: 3
+
+Function: Real part of "clog_towardzero":
+double: 2
+float: 2
+idouble: 2
+ifloat: 2
+ildouble: 3
+ldouble: 3
+
+Function: Imaginary part of "clog_towardzero":
+double: 1
+float: 2
+idouble: 1
+ifloat: 2
+ildouble: 4
+ldouble: 4
+
+Function: Real part of "clog_upward":
+double: 2
+float: 1
+idouble: 2
+ifloat: 1
+ildouble: 6
+ldouble: 6
+
+Function: Imaginary part of "clog_upward":
+double: 2
+float: 1
+idouble: 2
+ifloat: 1
+ildouble: 3
+ldouble: 3
+
 Function: "cos":
 double: 2
 float: 1
diff --git a/sysdeps/powerpc/powerpc32/fpu/s_nearbyint.S b/sysdeps/powerpc/powerpc32/fpu/s_nearbyint.S
index 2734738..05ab40e 100644
--- a/sysdeps/powerpc/powerpc32/fpu/s_nearbyint.S
+++ b/sysdeps/powerpc/powerpc32/fpu/s_nearbyint.S
@@ -53,17 +53,17 @@ ENTRY (__nearbyint)
 	fcmpu	cr7,fp1,fp12	/* if (x > 0.0 */
 	ble	cr7,L(lessthanzero)
 	mtfsb0	4*cr7+lt	/* Disable FE_INEXACT exception */
-	fadd	fp0,fp1,fp13	/* x += TWO52 */
-	fsub	fp1,fp0,fp13	/* x -= TWO52 */
+	fadd	fp1,fp1,fp13	/* x += TWO52 */
+	fsub	fp1,fp1,fp13	/* x -= TWO52 */
 	fabs	fp1,fp1		/* if (x == 0.0 */
 	mtfsb0	4*cr1+eq	/* Clear any FE_INEXACT exception */
 	blr
 L(lessthanzero):
 	bgelr	cr7
 	mtfsb0	4*cr7+lt	/* Disable FE_INEXACT exception */
-	fsub	fp0,fp13,fp1	/* x -= TWO52 */
-	fsub	fp0,fp0,fp13	/* x += TWO52 */
-	fneg	fp1,fp0		/* if (x == 0.0) */
+	fsub	fp1,fp1,fp13	/* x -= TWO52 */
+	fadd	fp1,fp1,fp13	/* x += TWO52 */
+	fnabs	fp1,fp1		/* if (x == 0.0) */
 	mtfsb0	4*cr1+eq	/* Clear any FE_INEXACT exception */
 	blr
 END (__nearbyint)
diff --git a/sysdeps/powerpc/powerpc32/fpu/s_nearbyintf.S b/sysdeps/powerpc/powerpc32/fpu/s_nearbyintf.S
index 11bdc77..7449a5f 100644
--- a/sysdeps/powerpc/powerpc32/fpu/s_nearbyintf.S
+++ b/sysdeps/powerpc/powerpc32/fpu/s_nearbyintf.S
@@ -52,16 +52,17 @@ ENTRY (__nearbyintf)
 	fcmpu	cr7,fp1,fp12		/* if (x > 0.0 */
 	ble	cr7,L(lessthanzero)
 	mtfsb0	4*cr7+lt		/* Disable FE_INEXACT exception */
-	fadds	fp0,fp1,fp13		/* x += TWO23 */
-	fsubs	fp1,fp0,fp13		/* x -= TWO23 */
+	fadds	fp1,fp1,fp13		/* x += TWO23 */
+	fsubs	fp1,fp1,fp13		/* x -= TWO23 */
+	fabs	fp1,fp1			/* if (x == 0.0) */
 	mtfsb0	4*cr1+eq		/* Clear any FE_INEXACT exception */
 	blr
 L(lessthanzero):
 	bgelr	cr7
 	mtfsb0	4*cr7+lt		/* Disable FE_INEXACT exception */
-	fsubs	fp0,fp13,fp1		/* x -= TWO23 */
-	fsubs	fp0,fp0,fp13		/* x += TWO23 */
-	fneg	fp1,fp0			/* if (x == 0.0) */
+	fsubs	fp1,fp1,fp13		/* x -= TWO23 */
+	fadds	fp1,fp1,fp13		/* x += TWO23 */
+	fnabs	fp1,fp1			/* if (x == 0.0) */
 	mtfsb0	4*cr1+eq		/* Clear any FE_INEXACT exception */
 	blr
 END (__nearbyintf)