[lldb-dev] [Bug 18594] New: MMX registers have incorrect values

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Thu Jan 23 12:27:22 PST 2014


            Bug ID: 18594
           Summary: MMX registers have incorrect values
           Product: lldb
           Version: 3.2
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: lldb-dev at cs.uiuc.edu
          Reporter: richard at codersnotes.com
    Classification: Unclassified

Created attachment 11926
  --> http://llvm.org/bugs/attachment.cgi?id=11926&action=edit
Program to demonstrate the bug

MMX registers are not aliased correctly with the floating point registers.

To reproduce, compile and run the attached program until it hits the int3

The program first prints the correct value of MM7 to stdout for reference. It
then performs the same test again except this time drops you at a breakpoint.

Type "register read mm7" into lldb. Compare against the value printed by the
test program. Notice they do not match.


$ clang fpbug.c -g -o fpbug
$ lldb fpbug
Current executable set to 'fpbug' (x86_64).
(lldb) run
Process 4301 launched: '/home/kayamon/fpbug' (x86_64)
MM7 should contain: c0e4000000000000
Process 4301 stopped
(lldb) register read mm7
     mm7 = 0x0000000000000000

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