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[FAST486]

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Implement FPTAN by calculating the sine and then dividing it by
the approximated cosine: sqrt(1 - sin(x) ^ 2).
This method turned out to be faster and more precise than the
Maclaurin series for tan(x), which converges very slowly.


svn path=/trunk/; revision=67932
This commit is contained in:
Aleksandar Andrejevic 2015-05-26 19:11:33 +00:00
parent 644884cece
commit d0860613d9
1 changed files with 20 additions and 6 deletions
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26
reactos/lib/fast486/fpu.c
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@ -1173,7 +1173,7 @@ Fast486FpuDivide(PFAST486_STATE State,
*/
static inline VOID FASTCALL
Fast486FpuCalculateTwoPowerMinusOne(PFAST486_STATE State,
PFAST486_FPU_DATA_REG Operand,
PCFAST486_FPU_DATA_REG Operand,
PFAST486_FPU_DATA_REG Result)
{
INT i;
@ -1221,7 +1221,7 @@ Fast486FpuCalculateTwoPowerMinusOne(PFAST486_STATE State,
static inline BOOLEAN FASTCALL
Fast486FpuCalculateLogBase2(PFAST486_STATE State,
PFAST486_FPU_DATA_REG Operand,
PCFAST486_FPU_DATA_REG Operand,
PFAST486_FPU_DATA_REG Result)
{
INT i;
@ -1345,7 +1345,7 @@ Cleanup:
*/
static inline BOOLEAN FASTCALL
Fast486FpuCalculateSine(PFAST486_STATE State,
PFAST486_FPU_DATA_REG Operand,
PCFAST486_FPU_DATA_REG Operand,
PFAST486_FPU_DATA_REG Result)
{
INT i;
@ -1425,7 +1425,7 @@ Fast486FpuCalculateSine(PFAST486_STATE State,
*/
static inline BOOLEAN FASTCALL
Fast486FpuCalculateCosine(PFAST486_STATE State,
PFAST486_FPU_DATA_REG Operand,
PCFAST486_FPU_DATA_REG Operand,
PFAST486_FPU_DATA_REG Result)
{
FAST486_FPU_DATA_REG Value = *Operand;
@ -2136,9 +2136,23 @@ FAST486_OPCODE_HANDLER(Fast486FpuOpcodeD9)
/* FPTAN */
case 0x32:
{
// TODO: NOT IMPLEMENTED
UNIMPLEMENTED;
FAST486_FPU_DATA_REG Sine;
FAST486_FPU_DATA_REG Cosine;
/* Compute the sine */
if (!Fast486FpuCalculateSine(State, &FPU_ST(0), &Sine)) break;
/* Find the cosine by calculating sqrt(1 - sin(x) ^ 2) */
if (!Fast486FpuMultiply(State, &Sine, &Sine, &Cosine)) break;
if (!Fast486FpuSubtract(State, &FpuOne, &Cosine, &Cosine)) break;
if (!Fast486FpuCalculateSquareRoot(State, &Cosine, &Cosine)) break;
/* Divide the sine by the cosine to get the tangent */
if (!Fast486FpuDivide(State, &Sine, &Cosine, &FPU_ST(0))) break;
FPU_UPDATE_TAG(0);
/* Push 1.00 */
Fast486FpuPush(State, &FpuOne);
break;
}