IMPYSL P,XT,loc32
6-108
Repeat This instruction is not repeatable. If this instruction follows the RPT
instruction, it resets the repeat counter (RPTC) and executes only once.
Example
; Calculate signed result:
; Y64 = (−X0*C0 − X1*C1 − X2*C2) >> 2
SPM −2 ; Set product shift mode to “>> 2”
ZAPA ; Zero ACC, P, OVCU
MOVL XT,@X0 ; XT = X0
IMPYL P,XT,@C0 ; P = low 32 bits of (X0*C0 << 2)
MOVL XT,@X1 ; XT = X1
IMPYSL P,XT,@C1 ; OVCU:ACC = OVCU:ACC − P,
; P = low 32 bits of (X1*C1 << 2)
MOVL XT,@X2 ; XT = X2
IMPYSL P,XT,@C2 ; OVCU:ACC = OVCU:ACC − P,
; P = low 32 bits of (X2*C2 << 2)
SUBUL ACC,@P ; OVCU:ACC = OVCU:ACC − P
MOVL @Y64+0,ACC ; Store low 32-bit result into Y64
MOVU @AL,OVC ; ACC = OVCU (borrow count)
MOVB AH,#0
NEG ACC ; Negate borrow
QMPYL P,XT,@C2 ; P = high 32 bits of (X2*C2)
MOVL XT,@X1 ; XT = X1
QMPYSL P,XT,@C1 ; ACC = ACC − P >> 2,|
; P = high 32 bits of (X1*C1)
MOVL XT,@X0 ; XT = X0
QMPYSL P,XT,@C0 ; ACC = ACC − P >> 2,
; P = high 32 bits of (X0*C0)
SUBL ACC,P << PM ; ACC = ACC − P >> 2
MOVL @Y64+2,ACC ; Store high 32-bit result into Y64
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