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[Bug math/13932] dbl-64 pow unexpectedly slow for some inputs
- From: "vincent-srcware at vinc17 dot net" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Mon, 12 Feb 2018 12:22:11 +0000
- Subject: [Bug math/13932] dbl-64 pow unexpectedly slow for some inputs
- Auto-submitted: auto-generated
- References: <bug-13932-131@http.sourceware.org/bugzilla/>
https://sourceware.org/bugzilla/show_bug.cgi?id=13932
--- Comment #14 from Vincent Lefèvre <vincent-srcware at vinc17 dot net> ---
Moreover, the code is quite horrible. mydefs.h defines:
typedef int int4;
typedef union { int4 i[2]; double x; } mynumber;
and in e_exp.c, it does bitwise operations on these signed int:
binexp.i[HIGH_HALF] = (junk1.i[LOW_HALF] + 1023) << 20;
i = ((junk2.i[LOW_HALF] >> 8) & 0xfffffffe) + 356;
j = (junk2.i[LOW_HALF] & 511) << 1;
which yield undefined or implementation-defined behavior. So I wonder whether
the generated code does what is expected.
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