24531904_j

pavg
図 2-31. 並列平均でのゼロから離れる方向の丸めの例
GR r 3 :
GR r 2 :
16 ビットの和
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キャリー
1 ビット
右シフト
GR r 1 :
操作 : if (PR[qp]) {
check_target_register(r 1);
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1 1 1 1
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if (one_byte_form) {
x[0] = GR[r 2]{7:0}; y[0] = GR[r 3]{7:0};
x[1] = GR[r 2 ]{15:8}; y[1] = GR[r 3 ]{15:8};
x[2] = GR[r 2 ]{23:16}; y[2] = GR[r 3 ]{23:16};
x[3] = GR[r 2]{31:24}; y[3] = GR[r 3]{31:24};
x[4] = GR[r 2 ]{39:32}; y[4] = GR[r 3 ]{39:32};
x[5] = GR[r 2 ]{47:40}; y[5] = GR[r 3 ]{47:40};
x[6] = GR[r 2]{55:48}; y[6] = GR[r 3]{55:48};
x[7] = GR[r 2 ]{63:56}; y[7] = GR[r 3 ]{63:56};
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pavg2.raz
if (raz_form) {
for (i = 0; i < 8; i++) {
temp[i] = zero_ext(x[i], 8) + zero_ext(y[i], 8) + 1;
res[i] = shift_right_unsigned(temp[i], 1);
}
} else { // normal form
for (i = 0; i < 8; i++) {
temp[i] = zero_ext(x[i], 8) + zero_ext(y[i], 8);
res[i] = shift_right_unsigned(temp[i], 1) | (temp[i]{0});
}
}
GR[r 1 ] = concatenate8(res[7], res[6], res[5], res[4],
res[3], res[2], res[1], res[0]);
} else { // two_byte_form
x[0] = GR[r 2 ]{15:0}; y[0] = GR[r 3 ]{15:0};
x[1] = GR[r 2 ]{31:16}; y[1] = GR[r 3 ]{31:16};
x[2] = GR[r 2 ]{47:32}; y[2] = GR[r 3 ]{47:32};
x[3] = GR[r 2 ]{63:48}; y[3] = GR[r 3 ]{63:48};
if (raz_form) {
for (i = 0; i < 4; i++) {
temp[i] = zero_ext(x[i], 16) + zero_ext(y[i], 16) + 1;
第 3 巻 : 命令リファレンス 3:181
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キャリー・
ビット
1 ビット右シフト
和ビット