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reversal of fsubp and fsubrp
From: |
dancie |
Subject: |
reversal of fsubp and fsubrp |
Date: |
Mon, 12 Nov 2007 08:03:23 -0800 (PST) |
I have noticed when debugging with gdb that the opcode "de e9" that (in intel
syntax) gdb gives out fsubrp st1,st0.
But according to the intel docs this fsubp st1,st0. I have also noticed that
the opcode for fsubrp st1,st0 gives out
fsubp st1,st0. I have not yet tried the other reverse pop instructions but
these two are switched. Here is a sample from
objdump output which gives an example:
000004b0 <etyBit>:
4b0: ba 01 00 00 00 mov $0x1,%edx
4b5: dd d8 fstp %st(0)
4b7: dd d8 fstp %st(0)
4b9: d9 ee fldz
4bb: dd dc fstp %st(4)
4bd: db 2d 00 00 00 00 fldt 0x0
4c3: db 3d 00 00 00 00 fstpt 0x0
4c9: db 2d 00 00 00 00 fldt 0x0
4cf: db 3d 00 00 00 00 fstpt 0x0
4d5: db 2d 00 00 00 00 fldt 0x0
4db: db 2d 00 00 00 00 fldt 0x0
4e1: de e9 fsubrp %st,%st(1) <---- Here is the error
4e3: da 35 00 00 00 00 fidivl 0x0
I first thought it was an error in gdb but a received an email from Daniel
Jacobowitz, from gdb. He said that is was
possibly an error in binutils.
Dancie Reeves
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- reversal of fsubp and fsubrp,
dancie <=