09.01.2013 Views

AMD x86-64 Architecture Programmer's Manual, Volume 4, 128-Bit ...

AMD x86-64 Architecture Programmer's Manual, Volume 4, 128-Bit ...

AMD x86-64 Architecture Programmer's Manual, Volume 4, 128-Bit ...

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

26568—Rev. 3.05—September 2003 <strong>AMD</strong><strong>64</strong> Technology<br />

UCOMISS Unordered Compare Scalar<br />

Single-Precision Floating-Point<br />

Performs an unordered compare of the single-precision floating-point value in the loworder<br />

32 bits of an XMM register with the single-precision floating-point value in the<br />

low-order 32 bits of another XMM register or a 32-bit memory location and sets the ZF,<br />

PF, and CF bits in the rFLAGS register to reflect the result. The result is unordered if<br />

one or both of the operand values is a NaN. The OF, AF, and SF bits in rFLAGS are set<br />

to zero.<br />

If the instruction causes an unmasked SIMD floating-point exception (#XF), the<br />

rFLAGS bits are not updated.<br />

Mnemonic Opcode Description<br />

UCOMISS xmm1, xmm2/mem32 0F 2E /r Compares scalar single-precision floating-point values in an XMM<br />

register and an XMM register or 32-bit memory location. Sets<br />

rFLAGS.<br />

xmm1 xmm2/mem32<br />

127 31 0 127 31<br />

0<br />

63<br />

0<br />

31<br />

compare<br />

rFLAGS<br />

Result of Compare ZF PF CF<br />

Unordered 1 1 1<br />

Greater Than 0 0 0<br />

Less Than 0 0 1<br />

Equal 1 0 0<br />

0<br />

ucomiss.eps<br />

UCOMISS 385

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!