[BZ4997]

	* sysdeps/powerpc/powerpc32/fpu/s_lround.S (__lround): Fixed erroneous
	result when x is +/-nextafter(+/-0.5,-/+1) i.e. all 1's in the
	mantissa.
	* sysdeps/powerpc/powerpc32/power4/fpu/s_llround.S (__llround):
	Likewise.  Also account for when x is an odd number between 2^52
	and 2^53-1.
	* sysdeps/powerpc/powerpc64/fpu/s_llround.S (__llround): Likewise.
	* sysdeps/powerpc/powerpc64/fpu/s_llroundf.S (__llroundf): Likewise.
	* math/libm-test.inc (lround_test, llround_test): Added test cases to
	detect aforementioned erroneous conditions.

1 files changed, 45 insertions, 26 deletions

diff --git a/sysdeps/powerpc/powerpc32/power4/fpu/s_llround.S b/sysdeps/powerpc/powerpc32/power4/fpu/s_llround.S
index 952d2aa6a5..4b1691efd3 100644
--- a/sysdeps/powerpc/powerpc32/power4/fpu/s_llround.S
+++ b/sysdeps/powerpc/powerpc32/power4/fpu/s_llround.S
@@ -1,5 +1,5 @@
 /* llround function.  PowerPC32 on PowerPC64 version.
-   Copyright (C) 2004, 2006 Free Software Foundation, Inc.
+   Copyright (C) 2004, 2006, 2007 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -20,15 +20,15 @@
 #include <sysdep.h>
 #include <math_ldbl_opt.h>
 
-	.section	.rodata.cst8,"aM",@progbits,8
-	.align	2
-.LC0:	/* 0.0 */
+ .section .rodata.cst12,"aM",@progbits,12
+ .align 3
+ .LC0:   /* 0x1.0000000000000p+52 == 2^52 */
+	.long 0x43300000
 	.long 0x00000000
-.LC1:	/* 0.5 */
-	.long 0x3f000000
+	.long 0x3f000000 /* Use this for 0.5  */
 
 	.section	".text"
-	
+
 /* long [r3] lround (float x [fp1])
    IEEE 1003.1 lround function.  IEEE specifies "round to the nearest 
    integer value, rounding halfway cases away from zero, regardless of
@@ -37,7 +37,15 @@
    tie, choose the one that is even (least significant bit o).". 
    So we can't use the PowerPC "round to Nearest" mode. Instead we set
    "round toward Zero" mode and round by adding +-0.5 before rounding
-   to the integer value.  */
+   to the integer value.
+
+   It is necessary to detect when x is (+-)0x1.fffffffffffffp-2
+   because adding +-0.5 in this case will cause an erroneous shift,
+   carry and round.  We simply return 0 if 0.5 > x > -0.5.  Likewise
+   if x is and odd number between +-(2^52 and 2^53-1) a shift and
+   carry will erroneously round if biased with +-0.5.  Therefore if x
+   is greater/less than +-2^52 we don't need to bias the number with
+   +-0.5.  */
 
 ENTRY (__llround)
 	stwu    r1,-16(r1)
@@ -57,30 +65,41 @@ ENTRY (__llround)
 # endif
 	mtlr	r11
 	cfi_same_value (lr)
-	lfs	fp12,0(r9)
-	lfs	fp10,.LC1-.LC0(r9)
+	lfd	fp9,0(r9)
+	lfs	fp10,8(r9)
 #else
-	lis	r9,.LC0@ha
-	lis	r10,.LC1@ha
-	lfs	fp12,.LC0@l(r9)
-	lfs	fp10,.LC1@l(r10)
+	lis r9,.LC0@ha
+	lfd fp9,.LC0@l(r9)	/* Load 2^52 into fpr9.  */
+	lfs fp10,.LC0@l+8(r9)	/* Load 0.5 into fpr10.  */
 #endif
-	fcmpu	cr6,fp1,fp12	/* if (x > 0.0)  */
-	ble-	cr6,.L4
-	fadd	fp1,fp1,fp10	/* x+= 0.5;  */
-.L9:
-	fctidz	fp2,fp1		/* Convert To Integer DW round toward 0.  */
-	stfd	fp2,8(r1)
-	nop	/* Ensure the following load is in a different dispatch  */
-	nop	/* group to avoid pipe stall on POWER4&5.  */
+	fabs	fp2,fp1		/* Get the absolute value of x.  */
+	fsub	fp12,fp10,fp10	/* Compute 0.0 into fpr12.  */
+	fcmpu	cr6,fp2,fp10	/* if |x| < 0.5  */
+	fcmpu	cr4,fp2,fp9	/* if |x| >= 2^52  */
+	fcmpu	cr3,fp1,fp12	/* x is negative? x < 0.0  */
+	blt-	cr6,.Lretzero	/* 0.5 > x < -0.5 so just return 0.  */
+	bge-	cr4,.Lnobias	/* 2^52 > x < -2^52 just convert with no bias.  */
+	fadd	fp3,fp2,fp10	/* |x|+=0.5 bias to prepare to round.  */
+	bge	cr3,.Lconvert	/* x is positive so don't negate x.  */
+	fnabs	fp3,fp3		/* -(|x|+=0.5)  */
+.Lconvert:
+	fctidz	fp4,fp3		/* Convert to Integer double word round toward 0.  */
+	stfd	fp4,8(r1)
+	nop
+	nop
 	nop
-	lwz	r4,12(r1)
+	lwz	r4,12(r1)	/* Load return as integer.  */
 	lwz	r3,8(r1)
+.Lout:
 	addi	r1,r1,16
 	blr
-.L4:
-	fsub	fp1,fp1,fp10	/* x-= 0.5;  */
-	b	.L9
+.Lretzero:			/* 0.5 > x > -0.5  */
+	li	r3,0		/* return 0.  */
+	li	r4,0
+	b	.Lout
+.Lnobias:
+	fmr	fp3,fp1
+	b	.Lconvert
 	END (__llround)
 
 weak_alias (__llround, llround)