Texas Instruments TMS320 2806 Series, Technical Reference Manual

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MCMPF32 MRa, #16FHi
32-Bit Floating-Point Compare for Equal, Less Than or Greater Than
Operands
MRa CLA floating-point source register (MR0 to MR3)
#16FHi A 16-bit immediate value that represents the upper 16-bits of an
IEEE 32-bit floating-point value. The low 16-bits of the mantissa
are assumed to be all 0.
Opcode
LSW: IIII IIII IIII IIII
MSW: 0111 1000 1100 00aa
Description Compare the value in MRa with the floating-point value represented by the immediate
operand. Set the ZF and NF flags on (MRa - #16FHi:0).
#16FHi is a 16-bit immediate value that represents the upper 16-bits of an IEEE 32-bit
floating-point value. The low 16-bits of the mantissa are assumed to be all 0. This
addressing mode is most useful for constants where the lowest 16-bits of the mantissa
are 0. Some examples are 2.0 (0x40000000), 4.0 (0x40800000), 0.5 (0x3F000000), and
-1.5 (0xBFC00000). The assembler will accept either a hex or float as the immediate
value. That is, -1.5 can be represented as #-1.5 or #0xBFC0.
The MCMPF32 instruction is performed as a logical compare operation. This is possible
because of the IEEE floating-point format offsets the exponent. Basically the bigger the
binary number, the bigger the floating-point value.
Special cases for inputs:
• Negative zero will be treated as positive zero.
• Denormalized value will be treated as positive zero.
• Not-a-Number (NaN) will be treated as infinity.
Flags This instruction modifies the following flags in the MSTF register:
Flag TF ZF NF LUF LVF
Modified No Yes Yes No No
The MSTF register flags are modified as follows:
If(MRa == #16FHi:0) {ZF=1, NF=0;}
If(MRa > #16FHi:0) {ZF=0, NF=0;}
If(MRa < #16FHi:0) {ZF=0, NF=1;}
Pipeline This is a single-cycle instruction
Example 1
; Behavior of ZF and NF flags for different comparisons
MMOVIZ MR1, #-2.0 ; MR1 = -2.0 (0xC0000000)
MMOVIZ MR0, #5.0 ; MR0 = 5.0 (0x40A00000)
MCMPF32 MR1, #-2.2 ; ZF = 0, NF = 0
MCMPF32 MR0, #6.5 ; ZF = 0, NF = 1
MCMPF32 MR0, #5.0 ; ZF = 1, NF = 0
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SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
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