https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=275322
Bug ID: 275322
Summary: Improper handling of mxcsr register during debug
(gdb/lldb)
Product: Base System
Version: 14.0-RELEASE
Hardware: Any
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: misc
Assignee: [email protected]
Reporter: [email protected]
Attachment #246554 text/plain
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Created attachment 246554
--> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=246554&action=edit
C code to demonstrate the problem
There is improper handling of the mxcsr register when debugging. It appears
that the current mxcsr register is not being given to the debugger.
The attached program illustrates the problem.
compile the attached program:lang -mfpmath=sse -mlong-double-64 -g -lm -o {x}
{x.c}
Run the following debug session:
gdb ./{x}
break main
run
** program should run to end with the following output:
ra=7.01209994486364354e-310 reatt=10000000000 ra * reatt-> result =0 savemxcsr
00001f80 mxcsr_set 00009fc0 showmxcsr 00009fc0 mxcsr 00001f80
disassemble main
** set a break at the mulsd instruction (should be around offset +81)
run
** should now be at the mulsd instruction
continue
** output should be the same as above
run
** should now be at the mulsd instruction
info register mxcsr
** output should be:
mxcsr 0x1f80 [ IM DM ZM OM UM PM ]
** which is incorrect since it there was a ldmxcsr instruction around offset
+39 and the result should be:
mxcsr 0x9fc0 [ DAZ IM DM ZM OM UM PM FZ ]
continue
** output shows incorrect output:
ra=7.01209994486364354e-310 reatt=10000000000 ra * reatt-> result
=7.01209994486364403e-300 savemxcsr 00001f80 mxcsr_set 00009fc0 showmxcsr
00009fc0 mxcsr 00001fa2
** since it appears that the mxcsr register is being reset back to the 0x1f80
value after it was displayed
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