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Diffstat (limited to 'docs/reference/asm_thumb2_float.rst')
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diff --git a/docs/reference/asm_thumb2_float.rst b/docs/reference/asm_thumb2_float.rst deleted file mode 100644 index 4acb734ee..000000000 --- a/docs/reference/asm_thumb2_float.rst +++ /dev/null @@ -1,77 +0,0 @@ -Floating Point instructions -============================== - -These instructions support the use of the ARM floating point coprocessor -(on platforms such as the Pyboard which are equipped with one). The FPU -has 32 registers known as ``s0-s31`` each of which can hold a single -precision float. Data can be passed between the FPU registers and the -ARM core registers with the ``vmov`` instruction. - -Note that MicroPython doesn't support passing floats to -assembler functions, nor can you put a float into ``r0`` and expect a -reasonable result. There are two ways to overcome this. The first is to -use arrays, and the second is to pass and/or return integers and convert -to and from floats in code. - -Document conventions --------------------- - -Notation: ``Sd, Sm, Sn`` denote FPU registers, ``Rd, Rm, Rn`` denote ARM core -registers. The latter can be any ARM core register although registers -``R13-R15`` are unlikely to be appropriate in this context. - -Arithmetic ----------- - -* vadd(Sd, Sn, Sm) ``Sd = Sn + Sm`` -* vsub(Sd, Sn, Sm) ``Sd = Sn - Sm`` -* vneg(Sd, Sm) ``Sd = -Sm`` -* vmul(Sd, Sn, Sm) ``Sd = Sn * Sm`` -* vdiv(Sd, Sn, Sm) ``Sd = Sn / Sm`` -* vsqrt(Sd, Sm) ``Sd = sqrt(Sm)`` - -Registers may be identical: ``vmul(S0, S0, S0)`` will execute ``S0 = S0*S0`` - -Move between ARM core and FPU registers ---------------------------------------- - -* vmov(Sd, Rm) ``Sd = Rm`` -* vmov(Rd, Sm) ``Rd = Sm`` - -The FPU has a register known as FPSCR, similar to the ARM core's APSR, which stores condition -codes plus other data. The following instructions provide access to this. - -* vmrs(APSR\_nzcv, FPSCR) - -Move the floating-point N, Z, C, and V flags to the APSR N, Z, C, and V flags. - -This is done after an instruction such as an FPU -comparison to enable the condition codes to be tested by the assembler -code. The following is a more general form of the instruction. - -* vmrs(Rd, FPSCR) ``Rd = FPSCR`` - -Move between FPU register and memory ------------------------------------- - -* vldr(Sd, [Rn, offset]) ``Sd = [Rn + offset]`` -* vstr(Sd, [Rn, offset]) ``[Rn + offset] = Sd`` - -Where ``[Rn + offset]`` denotes the memory address obtained by adding Rn to the offset. This -is specified in bytes. Since each float value occupies a 32 bit word, when accessing arrays of -floats the offset must always be a multiple of four bytes. - -Data Comparison ---------------- - -* vcmp(Sd, Sm) - -Compare the values in Sd and Sm and set the FPU N, Z, -C, and V flags. This would normally be followed by ``vmrs(APSR_nzcv, FPSCR)`` -to enable the results to be tested. - -Convert between integer and float ---------------------------------- - -* vcvt\_f32\_s32(Sd, Sm) ``Sd = float(Sm)`` -* vcvt\_s32\_f32(Sd, Sm) ``Sd = int(Sm)`` |