Major rewrite to handle special cases.

3 files changed, 618 insertions, 37 deletions

diff --git a/sysdeps/libm-i387/e_pow.S b/sysdeps/libm-i387/e_pow.S
index f6c7562d9c..efe184168b 100644
--- a/sysdeps/libm-i387/e_pow.S
+++ b/sysdeps/libm-i387/e_pow.S
@@ -1,5 +1,5 @@
 /* ix87 specific implementation of pow function.
-   Copyright (C) 1996 Free Software Foundation, Inc.
+   Copyright (C) 1996, 1997 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
 
@@ -27,31 +27,77 @@
 #endif
 
 	.align ALIGNARG(4)
+	ASM_TYPE_DIRECTIVE(infinity,@object)
+inf_zero:
+infinity:
+	.byte 0, 0, 0, 0, 0, 0, 0xf0, 0x7f
+	ASM_SIZE_DIRECTIVE(infinity)
+	ASM_TYPE_DIRECTIVE(zero,@object)
+zero:	.double 0.0
+	ASM_SIZE_DIRECTIVE(zero)
+	ASM_TYPE_DIRECTIVE(minf_mzero,@object)
+minf_mzero:
+minfinity:
+	.byte 0, 0, 0, 0, 0, 0, 0xf0, 0xff
+mzero:
+	.byte 0, 0, 0, 0, 0, 0, 0, 0x80
+	ASM_SIZE_DIRECTIVE(minf_mzero)
 	ASM_TYPE_DIRECTIVE(one,@object)
 one:	.double 1.0
 	ASM_SIZE_DIRECTIVE(one)
 	ASM_TYPE_DIRECTIVE(limit,@object)
 limit:	.double 0.29
 	ASM_SIZE_DIRECTIVE(limit)
+	ASM_TYPE_DIRECTIVE(nan,@object)
+nan:	.byte 0, 0, 0, 0, 0, 0, 0xff, 0x7f
+	ASM_SIZE_DIRECTIVE(nan)
 
 #ifdef PIC
 #define MO(op) op##@GOTOFF(%ecx)
+#define MOX(op,x,f) op##@GOTOFF(%ecx,x,f)
 #else
 #define MO(op) op
+#define MOX(op,x,f) op(,x,f)
 #endif
 
 	.text
 ENTRY(__ieee754_pow)
-	fldl	4(%esp)		// x
-	fldl	12(%esp)	// y : x
+	fldl	12(%esp)	// y
+	fxam
+	fnstsw
+	movb	%ah, %dl
+	andb	$0x45, %ah
+	cmpb	$0x40, %ah	// is y == 0 ?
+	je	11f
+
+	cmpb	$0x05, %ah	// is y == ±inf ?
+	je	12f
+
+	cmpb	$0x01, %ah	// is y == NaN ?
+	je	30f
 
 #ifdef	PIC
 	call	1f
 1:	popl	%ecx
 	addl	$_GLOBAL_OFFSET_TABLE_+[.-1b], %ecx
 #endif
+
+	fldl	4(%esp)		// x : y
+
 	subl	$8,%esp
 
+	fxam
+	fnstsw
+	movb	%ah, %dh
+	andb	$0x45, %ah
+	cmpb	$0x40, %ah
+	je	20f		// x is ±0
+
+	cmpb	$0x05, %ah
+	je	15f		// x is ±inf
+
+	fxch			// y : x
+
 	/* First see whether `y' is a natural number.  In this case we
 	   can use a more precise algorithm.  */
 	fld	%st		// y : y : x
@@ -63,13 +109,11 @@ ENTRY(__ieee754_pow)
 	jne	2f
 
 	/* OK, we have an integer value for y.  */
-	ftst			// y : x
-	fstp	%st(0)		// x
-	fnstsw
-	sahf
 	popl	%eax
 	popl	%edx
-	jnc	4f		// y >= 0, jump
+	orl	$0, %edx
+	fstp	%st(0)		// x
+	jns	4f		// y >= 0, jump
 	fdivrl	MO(one)		// 1/x		(now referred to as x)
 	negl	%eax
 	adcl	$0, %edx
@@ -87,7 +131,7 @@ ENTRY(__ieee754_pow)
 	orl	%edx, %ecx
 	jnz	6b
 	fstp	%st(0)		// ST*x
-	ret
+30:	ret
 
 	.align ALIGNARG(4)
 2:	/* y is a real number.  */
@@ -117,4 +161,161 @@ ENTRY(__ieee754_pow)
 	addl	$8, %esp
 	fstp	%st(1)		// 2^fract(y*log2(x))*2^int(y*log2(x))
 	ret
+
+
+	// pow(x,±0) = 1
+	.align ALIGNARG(4)
+11:	fstp	%st(0)		// pop y
+	fldl	MO(one)
+	ret
+
+	// y == ±inf
+	.align ALIGNARG(4)
+12:	fstp	%st(0)		// pop y
+	fldl	4(%esp)		// x
+	fabs
+	fcompl	MO(one)		// < 1, == 1, or > 1
+	fnstsw
+	andb	$0x45, %ah
+	cmpb	$0x45, %ah
+	je	13f		// jump if x is NaN
+
+	cmpb	$0x40, %ah
+	je	14f		// jump if |x| == 1
+
+	shlb	$1, %ah
+	xorb	%ah, %dl
+	andl	$2, %edx
+	fldl	MOX(inf_zero, %edx, 4)
+	ret
+
+	.align ALIGNARG(4)
+14:	fldl	MO(nan)
+	faddl	MO(zero)	// raise invalid exception
+	ret
+
+	.align ALIGNARG(4)
+13:	fldl	4(%esp)		// load x == NaN
+	ret
+
+	.align ALIGNARG(4)
+	// x is ±inf
+15:	fstp	%st(0)		// y
+	testb	$2, %dh
+	jz	16f		// jump if x == +inf
+
+	// We must find out whether y is an odd integer.
+	fld	%st		// y : y
+	fistpll	(%esp)		// y
+	fildll	(%esp)		// int(y) : y
+	fucompp			// <empty>
+	fnstsw
+	sahf
+	jne	17f
+
+	// OK, the value is an integer, but is the number of bits small
+	// enough so that all are coming from the mantissa?
+	popl	%eax
+	popl	%edx
+	andb	$1, %al
+	jz	18f		// jump if not odd
+	movl	%edx, %eax
+	orl	%edx, %edx
+	jns	155f
+	negl	%eax
+155:	cmpl	$0x00200000, %eax
+	ja	18f		// does not fit in mantissa bits
+	// It's an odd integer.
+	shrl	$31, %edx
+	fldl	MOX(minf_mzero, %edx, 8)
+	ret
+
+	.align ALIGNARG(4)
+16:	fcompl	MO(zero)
+	addl	$8, %esp
+	fnstsw
+	shrl	$5, %eax
+	andl	$8, %eax
+	fldl	MOX(inf_zero, %eax, 1)
+	ret
+
+	.align ALIGNARG(4)
+17:	shll	$30, %edx	// sign bit for y in right position
+	addl	$8, %esp
+18:	shrl	$31, %edx
+	fldl	MOX(inf_zero, %edx, 8)
+	ret
+
+	.align ALIGNARG(4)
+	// x is ±0
+20:	fstp	%st(0)		// y
+	testb	$2, %dl
+	jz	21f		// y > 0
+
+	// x is ±0 and y is < 0.  We must find out whether y is an odd integer.
+	testb	$2, %dh
+	jz	25f
+
+	fld	%st		// y : y
+	fistpll	(%esp)		// y
+	fildll	(%esp)		// int(y) : y
+	fucompp			// <empty>
+	fnstsw
+	sahf
+	jne	26f
+
+	// OK, the value is an integer, but is the number of bits small
+	// enough so that all are coming from the mantissa?
+	popl	%eax
+	popl	%edx
+	andb	$1, %al
+	jz	27f		// jump if not odd
+	cmpl	$0xffe00000, %edx
+	jbe	27f		// does not fit in mantissa bits
+	// It's an odd integer.
+	// Raise divide-by-zero exception and get minus infinity value.
+	fldl	MO(one)
+	fdivl	MO(zero)
+	fchs
+	ret
+
+25:	fstp	%st(0)
+26:	popl	%eax
+	popl	%edx
+27:	// Raise divide-by-zero exception and get infinity value.
+	fldl	MO(one)
+	fdivl	MO(zero)
+	ret
+
+	.align ALIGNARG(4)
+	// x is ±0 and y is > 0.  We must find out whether y is an odd integer.
+21:	testb	$2, %dh
+	jz	22f
+
+	fld	%st		// y : y
+	fistpll	(%esp)		// y
+	fildll	(%esp)		// int(y) : y
+	fucompp			// <empty>
+	fnstsw
+	sahf
+	jne	23f
+
+	// OK, the value is an integer, but is the number of bits small
+	// enough so that all are coming from the mantissa?
+	popl	%eax
+	popl	%edx
+	andb	$1, %al
+	jz	24f		// jump if not odd
+	cmpl	$0xffe00000, %edx
+	jbe	24f		// does not fit in mantissa bits
+	// It's an odd integer.
+	fldl	MO(mzero)
+	ret
+
+22:	fstp	%st(0)
+23:	popl	%eax
+	popl	%edx
+24:	fldl	MO(zero)
+	ret
+
 END(__ieee754_pow)
diff --git a/sysdeps/libm-i387/e_powf.S b/sysdeps/libm-i387/e_powf.S
index 9d6bc510b6..54af93c961 100644
--- a/sysdeps/libm-i387/e_powf.S
+++ b/sysdeps/libm-i387/e_powf.S
@@ -1,5 +1,5 @@
 /* ix87 specific implementation of pow function.
-   Copyright (C) 1996 Free Software Foundation, Inc.
+   Copyright (C) 1996, 1997 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
 
@@ -27,67 +27,107 @@
 #endif
 
 	.align ALIGNARG(4)
+	ASM_TYPE_DIRECTIVE(infinity,@object)
+inf_zero:
+infinity:
+	.byte 0, 0, 0, 0, 0, 0, 0xf0, 0x7f
+	ASM_SIZE_DIRECTIVE(infinity)
+	ASM_TYPE_DIRECTIVE(zero,@object)
+zero:	.double 0.0
+	ASM_SIZE_DIRECTIVE(zero)
+	ASM_TYPE_DIRECTIVE(minf_mzero,@object)
+minf_mzero:
+minfinity:
+	.byte 0, 0, 0, 0, 0, 0, 0xf0, 0xff
+mzero:
+	.byte 0, 0, 0, 0, 0, 0, 0, 0x80
+	ASM_SIZE_DIRECTIVE(minf_mzero)
 	ASM_TYPE_DIRECTIVE(one,@object)
 one:	.double 1.0
 	ASM_SIZE_DIRECTIVE(one)
 	ASM_TYPE_DIRECTIVE(limit,@object)
 limit:	.double 0.29
 	ASM_SIZE_DIRECTIVE(limit)
+	ASM_TYPE_DIRECTIVE(nan,@object)
+nan:	.byte 0, 0, 0, 0, 0, 0, 0xff, 0x7f
+	ASM_SIZE_DIRECTIVE(nan)
 
 #ifdef PIC
 #define MO(op) op##@GOTOFF(%ecx)
+#define MOX(op,x,f) op##@GOTOFF(%ecx,x,f)
 #else
 #define MO(op) op
+#define MOX(op,x,f) op(,x,f)
 #endif
 
 	.text
 ENTRY(__ieee754_powf)
-	flds	4(%esp)		// x
-	flds	8(%esp)		// y : x
+	flds	8(%esp)	// y
+	fxam
+	fnstsw
+	movb	%ah, %dl
+	andb	$0x45, %ah
+	cmpb	$0x40, %ah	// is y == 0 ?
+	je	11f
+
+	cmpb	$0x05, %ah	// is y == ±inf ?
+	je	12f
+
+	cmpb	$0x01, %ah	// is y == NaN ?
+	je	30f
 
 #ifdef	PIC
 	call	1f
 1:	popl	%ecx
 	addl	$_GLOBAL_OFFSET_TABLE_+[.-1b], %ecx
 #endif
-	subl	$8,%esp
+
+	flds	4(%esp)		// x : y
+
+	subl	$4, %esp
+
+	fxam
+	fnstsw
+	movb	%ah, %dh
+	andb	$0x45, %ah
+	cmpb	$0x40, %ah
+	je	20f		// x is ±0
+
+	cmpb	$0x05, %ah
+	je	15f		// x is ±inf
+
+	fxch			// y : x
 
 	/* First see whether `y' is a natural number.  In this case we
 	   can use a more precise algorithm.  */
 	fld	%st		// y : y : x
-	fistpll	(%esp)		// y : x
-	fildll	(%esp)		// int(y) : y : x
+	fistpl	(%esp)		// y : x
+	fildl	(%esp)		// int(y) : y : x
 	fucomp	%st(1)		// y : x
 	fnstsw
 	sahf
 	jne	2f
 
 	/* OK, we have an integer value for y.  */
-	ftst			// y : x
-	fstp	%st(0)		// x
-	fnstsw
-	sahf
-	popl	%eax
 	popl	%edx
-	jnc	4f		// y >= 0, jump
+	orl	$0, %edx
+	fstp	%st(0)		// x
+	jns	4f		// y >= 0, jump
 	fdivrl	MO(one)		// 1/x		(now referred to as x)
-	negl	%eax
-	adcl	$0, %edx
 	negl	%edx
 4:	fldl	MO(one)		// 1 : x
 	fxch
 
-6:	shrdl	$1, %edx, %eax
+6:	shrl	$1, %edx
 	jnc	5f
 	fxch
 	fmul	%st(1)		// x : ST*x
 	fxch
 5:	fmul	%st(0), %st	// x*x : ST*x
-	movl	%eax, %ecx
-	orl	%edx, %ecx
+	testl	%edx, %edx
 	jnz	6b
 	fstp	%st(0)		// ST*x
-	ret
+30:	ret
 
 	.align ALIGNARG(4)
 2:	/* y is a real number.  */
@@ -114,7 +154,159 @@ ENTRY(__ieee754_powf)
 	f2xm1			// 2^fract(y*log2(x))-1 : int(y*log2(x))
 	faddl	MO(one)		// 2^fract(y*log2(x)) : int(y*log2(x))
 	fscale			// 2^fract(y*log2(x))*2^int(y*log2(x)) : int(y*log2(x))
-	addl	$8, %esp
+	addl	$4, %esp
 	fstp	%st(1)		// 2^fract(y*log2(x))*2^int(y*log2(x))
 	ret
+
+
+	// pow(x,±0) = 1
+	.align ALIGNARG(4)
+11:	fstp	%st(0)		// pop y
+	fldl	MO(one)
+	ret
+
+	// y == ±inf
+	.align ALIGNARG(4)
+12:	fstp	%st(0)		// pop y
+	flds	4(%esp)		// x
+	fabs
+	fcompl	MO(one)		// < 1, == 1, or > 1
+	fnstsw
+	andb	$0x45, %ah
+	cmpb	$0x45, %ah
+	je	13f		// jump if x is NaN
+
+	cmpb	$0x40, %ah
+	je	14f		// jump if |x| == 1
+
+	shlb	$1, %ah
+	xorb	%ah, %dl
+	andl	$2, %edx
+	fldl	MOX(inf_zero, %edx, 4)
+	ret
+
+	.align ALIGNARG(4)
+14:	fldl	MO(nan)
+	faddl	MO(zero)	// raise invalid exception
+	ret
+
+	.align ALIGNARG(4)
+13:	flds	4(%esp)		// load x == NaN
+	ret
+
+	.align ALIGNARG(4)
+	// x is ±inf
+15:	fstp	%st(0)		// y
+	testb	$2, %dh
+	jz	16f		// jump if x == +inf
+
+	// We must find out whether y is an odd integer.
+	fld	%st		// y : y
+	fistpl	(%esp)		// y
+	fildl	(%esp)		// int(y) : y
+	fucompp			// <empty>
+	fnstsw
+	sahf
+	jne	17f
+
+	// OK, the value is an integer, but is the number of bits small
+	// enough so that all are coming from the mantissa?
+	popl	%edx
+	testb	$1, %dl
+	jz	18f		// jump if not odd
+	movl	%edx, %eax
+	orl	%edx, %edx
+	jns	155f
+	negl	%eax
+155:	cmpl	$0x01000000, %eax
+	ja	18f		// does not fit in mantissa bits
+	// It's an odd integer.
+	shrl	$31, %edx
+	fldl	MOX(minf_mzero, %edx, 8)
+	ret
+
+	.align ALIGNARG(4)
+16:	fcompl	MO(zero)
+	addl	$4, %esp
+	fnstsw
+	shrl	$5, %eax
+	andl	$8, %eax
+	fldl	MOX(inf_zero, %eax, 1)
+	ret
+
+	.align ALIGNARG(4)
+17:	shll	$30, %edx	// sign bit for y in right position
+	addl	$4, %esp
+18:	shrl	$31, %edx
+	fldl	MOX(inf_zero, %edx, 8)
+	ret
+
+	.align ALIGNARG(4)
+	// x is ±0
+20:	fstp	%st(0)		// y
+	testb	$2, %dl
+	jz	21f		// y > 0
+
+	// x is ±0 and y is < 0.  We must find out whether y is an odd integer.
+	testb	$2, %dh
+	jz	25f
+
+	fld	%st		// y : y
+	fistpl	(%esp)		// y
+	fildl	(%esp)		// int(y) : y
+	fucompp			// <empty>
+	fnstsw
+	sahf
+	jne	26f
+
+	// OK, the value is an integer, but is the number of bits small
+	// enough so that all are coming from the mantissa?
+	popl	%edx
+	testb	$1, %dl
+	jz	27f		// jump if not odd
+	cmpl	$0xff000000, %edx
+	jbe	27f		// does not fit in mantissa bits
+	// It's an odd integer.
+	// Raise divide-by-zero exception and get minus infinity value.
+	fldl	MO(one)
+	fdivl	MO(zero)
+	fchs
+	ret
+
+25:	fstp	%st(0)
+26:	popl	%eax
+27:	// Raise divide-by-zero exception and get infinity value.
+	fldl	MO(one)
+	fdivl	MO(zero)
+	ret
+
+	.align ALIGNARG(4)
+	// x is ±0 and y is > 0.  We must find out whether y is an odd integer.
+21:	testb	$2, %dh
+	jz	22f
+
+	fld	%st		// y : y
+	fistpl	(%esp)		// y
+	fildl	(%esp)		// int(y) : y
+	fucompp			// <empty>
+	fnstsw
+	sahf
+	jne	23f
+
+	// OK, the value is an integer, but is the number of bits small
+	// enough so that all are coming from the mantissa?
+	popl	%edx
+	testb	$1, %dl
+	jz	24f		// jump if not odd
+	cmpl	$0xff000000, %edx
+	jbe	24f		// does not fit in mantissa bits
+	// It's an odd integer.
+	fldl	MO(mzero)
+	ret
+
+22:	fstp	%st(0)
+23:	popl	%eax
+24:	fldl	MO(zero)
+	ret
+
 END(__ieee754_powf)
diff --git a/sysdeps/libm-i387/e_powl.S b/sysdeps/libm-i387/e_powl.S
index ea445804f0..3cfb96b213 100644
--- a/sysdeps/libm-i387/e_powl.S
+++ b/sysdeps/libm-i387/e_powl.S
@@ -1,5 +1,5 @@
 /* ix87 specific implementation of pow function.
-   Copyright (C) 1996 Free Software Foundation, Inc.
+   Copyright (C) 1996, 1997 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
 
@@ -27,31 +27,77 @@
 #endif
 
 	.align ALIGNARG(4)
+	ASM_TYPE_DIRECTIVE(infinity,@object)
+inf_zero:
+infinity:
+	.byte 0, 0, 0, 0, 0, 0, 0xf0, 0x7f
+	ASM_SIZE_DIRECTIVE(infinity)
+	ASM_TYPE_DIRECTIVE(zero,@object)
+zero:	.double 0.0
+	ASM_SIZE_DIRECTIVE(zero)
+	ASM_TYPE_DIRECTIVE(minf_mzero,@object)
+minf_mzero:
+minfinity:
+	.byte 0, 0, 0, 0, 0, 0, 0xf0, 0xff
+mzero:
+	.byte 0, 0, 0, 0, 0, 0, 0, 0x80
+	ASM_SIZE_DIRECTIVE(minf_mzero)
 	ASM_TYPE_DIRECTIVE(one,@object)
 one:	.double 1.0
 	ASM_SIZE_DIRECTIVE(one)
 	ASM_TYPE_DIRECTIVE(limit,@object)
 limit:	.double 0.29
 	ASM_SIZE_DIRECTIVE(limit)
+	ASM_TYPE_DIRECTIVE(nan,@object)
+nan:	.byte 0, 0, 0, 0, 0, 0, 0xff, 0x7f
+	ASM_SIZE_DIRECTIVE(nan)
 
 #ifdef PIC
 #define MO(op) op##@GOTOFF(%ecx)
+#define MOX(op,x,f) op##@GOTOFF(%ecx,x,f)
 #else
 #define MO(op) op
+#define MOX(op,x,f) op(,x,f)
 #endif
 
 	.text
 ENTRY(__ieee754_powl)
-	fldt	4(%esp)		// x
-	fldt	16(%esp)	// y : x
+	fldt	16(%esp)	// y
+	fxam
+	fnstsw
+	movb	%ah, %dl
+	andb	$0x45, %ah
+	cmpb	$0x40, %ah	// is y == 0 ?
+	je	11f
+
+	cmpb	$0x05, %ah	// is y == ±inf ?
+	je	12f
+
+	cmpb	$0x01, %ah	// is y == NaN ?
+	je	30f
 
 #ifdef	PIC
 	call	1f
 1:	popl	%ecx
 	addl	$_GLOBAL_OFFSET_TABLE_+[.-1b], %ecx
 #endif
+
+	fldt	4(%esp)		// x : y
+
 	subl	$8,%esp
 
+	fxam
+	fnstsw
+	movb	%ah, %dh
+	andb	$0x45, %ah
+	cmpb	$0x40, %ah
+	je	20f		// x is ±0
+
+	cmpb	$0x05, %ah
+	je	15f		// x is ±inf
+
+	fxch			// y : x
+
 	/* First see whether `y' is a natural number.  In this case we
 	   can use a more precise algorithm.  */
 	fld	%st		// y : y : x
@@ -63,13 +109,11 @@ ENTRY(__ieee754_powl)
 	jne	2f
 
 	/* OK, we have an integer value for y.  */
-	ftst			// y : x
-	fstp	%st(0)		// x
-	fnstsw
-	sahf
 	popl	%eax
 	popl	%edx
-	jnc	4f		// y >= 0, jump
+	orl	$0, %edx
+	fstp	%st(0)		// x
+	jns	4f		// y >= 0, jump
 	fdivrl	MO(one)		// 1/x		(now referred to as x)
 	negl	%eax
 	adcl	$0, %edx
@@ -87,7 +131,7 @@ ENTRY(__ieee754_powl)
 	orl	%edx, %ecx
 	jnz	6b
 	fstp	%st(0)		// ST*x
-	ret
+30:	ret
 
 	.align ALIGNARG(4)
 2:	/* y is a real number.  */
@@ -117,4 +161,148 @@ ENTRY(__ieee754_powl)
 	addl	$8, %esp
 	fstp	%st(1)		// 2^fract(y*log2(x))*2^int(y*log2(x))
 	ret
+
+
+	// pow(x,±0) = 1
+	.align ALIGNARG(4)
+11:	fstp	%st(0)		// pop y
+	fldl	MO(one)
+	ret
+
+	// y == ±inf
+	.align ALIGNARG(4)
+12:	fstp	%st(0)		// pop y
+	fldt	4(%esp)		// x
+	fabs
+	fcompl	MO(one)		// < 1, == 1, or > 1
+	fnstsw
+	andb	$0x45, %ah
+	cmpb	$0x45, %ah
+	je	13f		// jump if x is NaN
+
+	cmpb	$0x40, %ah
+	je	14f		// jump if |x| == 1
+
+	shlb	$1, %ah
+	xorb	%ah, %dl
+	andl	$2, %edx
+	fldl	MOX(inf_zero, %edx, 4)
+	ret
+
+	.align ALIGNARG(4)
+14:	fldl	MO(nan)
+	faddl	MO(zero)	// raise invalid exception
+	ret
+
+	.align ALIGNARG(4)
+13:	fldt	4(%esp)		// load x == NaN
+	ret
+
+	.align ALIGNARG(4)
+	// x is ±inf
+15:	fstp	%st(0)		// y
+	testb	$2, %dh
+	jz	16f		// jump if x == +inf
+
+	// We must find out whether y is an odd integer.
+	fld	%st		// y : y
+	fistpll	(%esp)		// y
+	fildll	(%esp)		// int(y) : y
+	fucompp			// <empty>
+	fnstsw
+	sahf
+	jne	17f
+
+	// OK, the value is an integer, but is it odd?
+	popl	%eax
+	popl	%edx
+	andb	$1, %al
+	jz	18f		// jump if not odd
+	// It's an odd integer.
+	shrl	$31, %edx
+	fldl	MOX(minf_mzero, %edx, 8)
+	ret
+
+	.align ALIGNARG(4)
+16:	fcompl	MO(zero)
+	addl	$8, %esp
+	fnstsw
+	shrl	$5, %eax
+	andl	$8, %eax
+	fldl	MOX(inf_zero, %eax, 1)
+	ret
+
+	.align ALIGNARG(4)
+17:	shll	$30, %edx	// sign bit for y in right position
+	addl	$8, %esp
+18:	shrl	$31, %edx
+	fldl	MOX(inf_zero, %edx, 8)
+	ret
+
+	.align ALIGNARG(4)
+	// x is ±0
+20:	fstp	%st(0)		// y
+	testb	$2, %dl
+	jz	21f		// y > 0
+
+	// x is ±0 and y is < 0.  We must find out whether y is an odd integer.
+	testb	$2, %dh
+	jz	25f
+
+	fld	%st		// y : y
+	fistpll	(%esp)		// y
+	fildll	(%esp)		// int(y) : y
+	fucompp			// <empty>
+	fnstsw
+	sahf
+	jne	26f
+
+	// OK, the value is an integer, but is it odd?
+	popl	%eax
+	popl	%edx
+	andb	$1, %al
+	jz	27f		// jump if not odd
+	// It's an odd integer.
+	// Raise divide-by-zero exception and get minus infinity value.
+	fldl	MO(one)
+	fdivl	MO(zero)
+	fchs
+	ret
+
+25:	fstp	%st(0)
+26:	popl	%eax
+	popl	%edx
+27:	// Raise divide-by-zero exception and get infinity value.
+	fldl	MO(one)
+	fdivl	MO(zero)
+	ret
+
+	.align ALIGNARG(4)
+	// x is ±0 and y is > 0.  We must find out whether y is an odd integer.
+21:	testb	$2, %dh
+	jz	22f
+
+	fld	%st		// y : y
+	fistpll	(%esp)		// y
+	fildll	(%esp)		// int(y) : y
+	fucompp			// <empty>
+	fnstsw
+	sahf
+	jne	23f
+
+	// OK, the value is an integer, but is it odd?
+	popl	%eax
+	popl	%edx
+	andb	$1, %al
+	jz	24f		// jump if not odd
+	// It's an odd integer.
+	fldl	MO(mzero)
+	ret
+
+22:	fstp	%st(0)
+23:	popl	%eax
+	popl	%edx
+24:	fldl	MO(zero)
+	ret
+
 END(__ieee754_powl)