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Fix spurious "inexact" exceptions from x86 pow with NaN argument (bug 16167)
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: <libc-alpha at sourceware dot org>
- Date: Wed, 13 Nov 2013 18:15:00 +0000
- Subject: Fix spurious "inexact" exceptions from x86 pow with NaN argument (bug 16167)
- Authentication-results: sourceware.org; auth=none
Bug 16167 is x86 / x86_64 pow functions wrongly raising the "inexact"
exception for some cases of NaN input, when according to ISO C NaN
inputs returning NaN outputs should generally raise no exceptions at
all. This patch adds appropriate tests for this case to the
implementations.
Tested x86_64 and x86, together with my separate patch to make
libm-test.inc check this ISO C requirement (intended to go in
immediately after this one).
2013-11-13 Joseph Myers <joseph@codesourcery.com>
[BZ #16167]
* sysdeps/i386/fpu/e_pow.S (__ieee754_pow): Check for first
argument being NaN and avoid computations with second argument in
that case.
* sysdeps/i386/fpu/e_powf.S (__ieee754_powf): Likewise.
* sysdeps/i386/fpu/e_powl.S (__ieee754_powl): Likewise.
* sysdeps/x86_64/fpu/e_powl.S (__ieee754_powl): Likewise.
diff --git a/sysdeps/i386/fpu/e_pow.S b/sysdeps/i386/fpu/e_pow.S
index 109c395..835c39b 100644
--- a/sysdeps/i386/fpu/e_pow.S
+++ b/sysdeps/i386/fpu/e_pow.S
@@ -98,6 +98,9 @@ ENTRY(__ieee754_pow)
cmpb $0x05, %ah
je 15f // x is ħinf
+ cmpb $0x01, %ah
+ je 32f // x is NaN
+
fxch // y : x
/* fistpll raises invalid exception for |y| >= 1L<<63. */
@@ -166,6 +169,12 @@ ENTRY(__ieee754_pow)
ret
cfi_adjust_cfa_offset (8)
+32: addl $8, %esp
+ cfi_adjust_cfa_offset (-8)
+ fstp %st(1)
+ ret
+
+ cfi_adjust_cfa_offset (8)
.align ALIGNARG(4)
2: // y is a large integer (absolute value at least 1L<<10), but
// may be odd unless at least 1L<<64. So it may be necessary
diff --git a/sysdeps/i386/fpu/e_powf.S b/sysdeps/i386/fpu/e_powf.S
index 7fad90f..90d3d0c 100644
--- a/sysdeps/i386/fpu/e_powf.S
+++ b/sysdeps/i386/fpu/e_powf.S
@@ -95,6 +95,9 @@ ENTRY(__ieee754_powf)
cmpb $0x05, %ah
je 15f // x is ħinf
+ cmpb $0x01, %ah
+ je 32f // x is NaN
+
fxch // y : x
/* fistpl raises invalid exception for |y| >= 1L<<31. */
@@ -180,7 +183,7 @@ 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 $4, %esp
+32: addl $4, %esp
cfi_adjust_cfa_offset (-4)
fstp %st(1) // 2^fract(y*log2(x))*2^int(y*log2(x))
ret
diff --git a/sysdeps/i386/fpu/e_powl.S b/sysdeps/i386/fpu/e_powl.S
index 3c23117..91e22c8 100644
--- a/sysdeps/i386/fpu/e_powl.S
+++ b/sysdeps/i386/fpu/e_powl.S
@@ -104,6 +104,9 @@ ENTRY(__ieee754_powl)
cmpb $0x05, %ah
je 15f // x is ħinf
+ cmpb $0x01, %ah
+ je 32f // x is NaN
+
fxch // y : x
/* fistpll raises invalid exception for |y| >= 1L<<63. */
@@ -188,6 +191,12 @@ ENTRY(__ieee754_powl)
ret
cfi_adjust_cfa_offset (8)
+32: addl $8, %esp
+ cfi_adjust_cfa_offset (-8)
+ fstp %st(1)
+ ret
+
+ cfi_adjust_cfa_offset (8)
.align ALIGNARG(4)
2: // y is a large integer (absolute value at least 8), but
// may be odd unless at least 1L<<64. So it may be necessary
diff --git a/sysdeps/x86_64/fpu/e_powl.S b/sysdeps/x86_64/fpu/e_powl.S
index e101726..590223b 100644
--- a/sysdeps/x86_64/fpu/e_powl.S
+++ b/sysdeps/x86_64/fpu/e_powl.S
@@ -96,6 +96,9 @@ ENTRY(__ieee754_powl)
cmpb $0x05, %ah
je 15f // x is ħinf
+ cmpb $0x01, %ah
+ je 31f // x is NaN
+
fxch // y : x
/* fistpll raises invalid exception for |y| >= 1L<<63. */
--
Joseph S. Myers
joseph@codesourcery.com