指令vector search的格式和功能是什么

zuohuanhuan

英文的看不大明白，牛人的给翻译一下下。。。
This instruction is used in a loop to locate a maximum or minimum ele-
ment in an array of 16-bit packed data. Two values are tested at a time.
The Vector Search instruction compares two 16-bit, signed half-words to
values stored in the Accumulators. Then, it conditionally updates each
Accumulator and destination pointer based on the comparison.
Pointer register P0 is always the implied array pointer for the elements
being searched.
More specifically, the signed high half-word of src_reg is compared in
magnitude with the 16 low-order bits in A1. If src_reg_hi meets the com-
parison criterion, then A1 is updated with src_reg_hi, and the value in
pointer register P0 is stored in dest_pointer_hi. The same operation is
performed for src_reg_low and A0.
Based on the search mode specified in the syntax, the instruction tests for
maximum or minimum signed values.
Values are sign extended when copied into the Accumulator(s).
See “Example” for one way to implement the search loop. After the vector
search loop concludes, A1 and A0 hold the two surviving elements, and
dest_pointer_hi and dest_pointer_lo contain their respective addresses.
The next step is to select the final value from these two surviving elements.
Example
/* Initialize Accumulators with appropriate value for the type of
search. */
r0.l=0x7fff ;
r0.h=0 ;
a0=r0 ; /* max positive 16-bit value */
a1=r0 ; /* max positive 16-bit value */
/* Initialize R2. */
r2=[p0++] ;
/* Assume P1 is initialized to the size of the vector length. */
LSETUP (loop_, loop_) LC0=P1>>1 ; /* set up the loop */
loop_: (r1,r0) = SEARCH R2 (LE) || R2=[P0++];
/* search for the last minimum in all but the
last element of the array */
(r1,r0) = SEARCH R2 (LE);
/* finally, search the last element */
/* The lower 16 bits of A1 and A0 contain the last minimums of the
array. R1 contains the value of P0 corresponding to the value in
A1. R0 contains the value of P0 corresponding to the value in A0.
Next, compare A1 and A0 together and R1 and R0 together to find
the single, last minimum in the array.
Note: In this example, the resulting pointers are past the actual
surviving array element due to the post-increment operation. */
cc = a0 <= a1 ;
r0 += -4 ;
r1 += -2 ;
if !cc r0 = r1 ; /* the pointer to the survivor is in r0 */