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Unified Diff: runtime/vm/intrinsifier_arm64.cc

Issue 817583003: Process two 32-bit digits as one 64-bit digit in all bigint intrinsics on ARM64. (Closed) Base URL: http://dart.googlecode.com/svn/branches/bleeding_edge/dart/
Patch Set: Created 5 years, 11 months ago
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Index: runtime/vm/intrinsifier_arm64.cc
===================================================================
--- runtime/vm/intrinsifier_arm64.cc (revision 42607)
+++ runtime/vm/intrinsifier_arm64.cc (working copy)
@@ -931,27 +931,28 @@
// static int _mulAdd(Uint32List x_digits, int xi,
// Uint32List m_digits, int i,
// Uint32List a_digits, int j, int n) {
- // uint32_t x = x_digits[xi >> 1]; // xi is Smi.
+ // uint64_t x = x_digits[xi >> 1 .. (xi >> 1) + 1]; // xi is Smi and even.
// if (x == 0 || n == 0) {
- // return 1;
+ // return 2;
// }
- // uint32_t* mip = &m_digits[i >> 1]; // i is Smi.
- // uint32_t* ajp = &a_digits[j >> 1]; // j is Smi.
- // uint32_t c = 0;
- // SmiUntag(n);
+ // uint64_t* mip = &m_digits[i >> 1]; // i is Smi and even.
+ // uint64_t* ajp = &a_digits[j >> 1]; // j is Smi and even.
+ // uint64_t c = 0;
+ // SmiUntag(n); // n is Smi and even.
+ // n = (n + 1)/2; // Number of pairs to process.
// do {
- // uint32_t mi = *mip++;
- // uint32_t aj = *ajp;
- // uint64_t t = x*mi + aj + c; // 32-bit * 32-bit -> 64-bit.
- // *ajp++ = low32(t);
- // c = high32(t);
+ // uint64_t mi = *mip++;
+ // uint64_t aj = *ajp;
+ // uint128_t t = x*mi + aj + c; // 64-bit * 64-bit -> 128-bit.
+ // *ajp++ = low64(t);
+ // c = high64(t);
// } while (--n > 0);
// while (c != 0) {
- // uint64_t t = *ajp + c;
- // *ajp++ = low32(t);
- // c = high32(t); // c == 0 or 1.
+ // uint128_t t = *ajp + c;
+ // *ajp++ = low64(t);
+ // c = high64(t); // c == 0 or 1.
// }
- // return 1;
+ // return 2;
// }
Label done;
@@ -959,13 +960,14 @@
// R0 = xi as Smi, R1 = x_digits.
__ ldp(R0, R1, Address(SP, 5 * kWordSize, Address::PairOffset));
__ add(R1, R1, Operand(R0, LSL, 1));
- __ ldr(R3, FieldAddress(R1, TypedData::data_offset()), kUnsignedWord);
+ __ ldr(R3, FieldAddress(R1, TypedData::data_offset()));
__ tst(R3, Operand(R3));
__ b(&done, EQ);
- // R6 = SmiUntag(n), no_op if n == 0
+ // R6 = (SmiUntag(n) + 1)/2, no_op if n == 0
__ ldr(R6, Address(SP, 0 * kWordSize));
- __ adds(R6, ZR, Operand(R6, ASR, kSmiTagSize)); // SmiUntag(R6) and set cc.
+ __ add(R6, R6, Operand(2));
+ __ adds(R6, ZR, Operand(R6, ASR, 2)); // SmiUntag(R6) and set cc.
__ b(&done, EQ);
// R4 = mip = &m_digits[i >> 1]
@@ -990,25 +992,25 @@
// ajp: R5
// c: R1
// n: R6
+ // t: R7:R8 (not live at loop entry)
- // uint32_t mi = *mip++
- __ ldr(R2, Address(R4, Bigint::kBytesPerDigit, Address::PostIndex),
- kUnsignedWord);
+ // uint64_t mi = *mip++
+ __ ldr(R2, Address(R4, 2*Bigint::kBytesPerDigit, Address::PostIndex));
- // uint32_t aj = *ajp
- __ ldr(R0, Address(R5, 0), kUnsignedWord);
+ // uint64_t aj = *ajp
+ __ ldr(R0, Address(R5, 0));
- // uint64_t t = x*mi + aj + c
- __ umaddl(R0, R2, R3, R0); // X0 = W2*W3 + X0.
- __ add(R0, R0, Operand(R1)); // R0 += c.
+ // uint128_t t = x*mi + aj + c
+ __ mul(R7, R2, R3); // R7 = low64(R2*R3).
+ __ umulh(R8, R2, R3); // R8 = high64(R2*R3), t = R8:R7 = x*mi.
+ __ adds(R7, R7, Operand(R0));
+ __ adc(R8, R8, ZR); // t += aj.
+ __ adds(R0, R7, Operand(R1)); // t += c, R0 = low64(t).
+ __ adc(R1, R8, ZR); // c = R1 = high64(t).
- // *ajp++ = low32(t) = R0
- __ str(R0, Address(R5, Bigint::kBytesPerDigit, Address::PostIndex),
- kUnsignedWord);
+ // *ajp++ = low64(t) = R0
+ __ str(R0, Address(R5, 2*Bigint::kBytesPerDigit, Address::PostIndex));
- // c = R1 = high32(t) = R0 >> 32.
- __ LsrImmediate(R1, R0, 32);
-
// while (--n > 0)
__ subs(R6, R6, Operand(1)); // --n
__ b(&muladd_loop, NE);
@@ -1017,22 +1019,20 @@
__ b(&done, EQ);
// *ajp++ += c
- __ ldr(R0, Address(R5, 0), kUnsignedWord);
- __ addsw(R0, R0, Operand(R1));
- __ str(R0, Address(R5, Bigint::kBytesPerDigit, Address::PostIndex),
- kUnsignedWord);
+ __ ldr(R0, Address(R5, 0));
+ __ adds(R0, R0, Operand(R1));
+ __ str(R0, Address(R5, 2*Bigint::kBytesPerDigit, Address::PostIndex));
__ b(&done, CC);
Label propagate_carry_loop;
__ Bind(&propagate_carry_loop);
- __ ldr(R0, Address(R5, 0), kUnsignedWord);
- __ addsw(R0, R0, Operand(1));
- __ str(R0, Address(R5, Bigint::kBytesPerDigit, Address::PostIndex),
- kUnsignedWord);
+ __ ldr(R0, Address(R5, 0));
+ __ adds(R0, R0, Operand(1));
+ __ str(R0, Address(R5, 2*Bigint::kBytesPerDigit, Address::PostIndex));
__ b(&propagate_carry_loop, CS);
__ Bind(&done);
- __ LoadImmediate(R0, Smi::RawValue(1), kNoPP); // One digit processed.
+ __ LoadImmediate(R0, Smi::RawValue(2), kNoPP); // Two digits processed.
__ ret();
}
@@ -1041,27 +1041,27 @@
// Pseudo code:
// static int _sqrAdd(Uint32List x_digits, int i,
// Uint32List a_digits, int used) {
- // uint32_t* xip = &x_digits[i >> 1]; // i is Smi.
- // uint32_t x = *xip++;
- // if (x == 0) return 1;
- // uint32_t* ajp = &a_digits[i]; // j == 2*i, i is Smi.
- // uint32_t aj = *ajp;
- // uint64_t t = x*x + aj;
- // *ajp++ = low32(t);
- // uint64_t c = high32(t);
- // int n = ((used - i) >> 1) - 1; // used and i are Smi.
+ // uint64_t* xip = &x_digits[i >> 1]; // i is Smi and even.
+ // uint64_t x = *xip++;
+ // if (x == 0) return 2;
+ // uint64_t* ajp = &a_digits[i]; // j == 2*i, i is Smi.
+ // uint64_t aj = *ajp;
+ // uint128_t t = x*x + aj;
+ // *ajp++ = low64(t);
+ // uint128_t c = high64(t);
+ // int n = ((used - i + 2) >> 2) - 1; // used and i are Smi. n: num pairs.
// while (--n >= 0) {
- // uint32_t xi = *xip++;
- // uint32_t aj = *ajp;
- // uint96_t t = 2*x*xi + aj + c; // 2-bit * 32-bit * 32-bit -> 65-bit.
- // *ajp++ = low32(t);
- // c = high64(t); // 33-bit.
+ // uint64_t xi = *xip++;
+ // uint64_t aj = *ajp;
+ // uint192_t t = 2*x*xi + aj + c; // 2-bit * 64-bit * 64-bit -> 129-bit.
+ // *ajp++ = low64(t);
+ // c = high128(t); // 65-bit.
// }
- // uint32_t aj = *ajp;
- // uint64_t t = aj + c; // 32-bit + 33-bit -> 34-bit.
- // *ajp++ = low32(t);
- // *ajp = high32(t);
- // return 1;
+ // uint64_t aj = *ajp;
+ // uint128_t t = aj + c; // 64-bit + 65-bit -> 66-bit.
+ // *ajp++ = low64(t);
+ // *ajp = high64(t);
+ // return 2;
// }
// R4 = xip = &x_digits[i >> 1]
@@ -1072,8 +1072,7 @@
// R3 = x = *xip++, return if x == 0
Label x_zero;
- __ ldr(R3, Address(R4, Bigint::kBytesPerDigit, Address::PostIndex),
- kUnsignedWord);
+ __ ldr(R3, Address(R4, 2*Bigint::kBytesPerDigit, Address::PostIndex));
__ tst(R3, Operand(R3));
__ b(&x_zero, EQ);
@@ -1082,22 +1081,23 @@
__ add(R1, R1, Operand(R2, LSL, 2)); // j == 2*i, i is Smi.
__ add(R5, R1, Operand(TypedData::data_offset() - kHeapObjectTag));
- // X0 = t = x*x + *ajp
- __ ldr(R0, Address(R5, 0), kUnsignedWord);
- __ umaddl(R0, R3, R3, R0); // X0 = W3*W3 + X0.
+ // R6:R1 = t = x*x + *ajp
+ __ ldr(R0, Address(R5, 0));
+ __ mul(R1, R3, R3); // R1 = low64(R3*R3).
+ __ umulh(R6, R3, R3); // R6 = high64(R3*R3).
+ __ adds(R1, R1, Operand(R0)); // R6:R1 += *ajp.
+ __ adc(R6, R6, ZR); // R6 = low64(c) = high64(t).
+ __ mov(R7, ZR); // R7 = high64(c) = 0.
- // *ajp++ = low32(t) = R0
- __ str(R0, Address(R5, Bigint::kBytesPerDigit, Address::PostIndex),
- kUnsignedWord);
+ // *ajp++ = low64(t) = R1
+ __ str(R1, Address(R5, 2*Bigint::kBytesPerDigit, Address::PostIndex));
- // c = R6 = high32(t) = R0 >> 32.
- __ LsrImmediate(R6, R0, 32);
-
- // int n = used - i - 1
+ // int n = (used - i + 1)/2 - 1
__ ldr(R0, Address(SP, 0 * kWordSize)); // used is Smi
__ sub(R8, R0, Operand(R2));
+ __ add(R8, R8, Operand(2));
__ movn(R0, Immediate(1), 0); // R0 = ~1 = -2.
- __ adds(R8, R0, Operand(R8, ASR, kSmiTagSize)); // while (--n >= 0)
+ __ adds(R8, R0, Operand(R8, ASR, 2)); // while (--n >= 0)
Label loop, done;
__ b(&done, MI);
@@ -1106,89 +1106,111 @@
// x: R3
// xip: R4
// ajp: R5
- // c: R6
- // t: R1:R0 (not live at loop entry)
+ // c: R7:R6
+ // t: R2:R1:R0 (not live at loop entry)
// n: R8
- // uint32_t xi = *xip++
- __ ldr(R2, Address(R4, Bigint::kBytesPerDigit, Address::PostIndex),
- kUnsignedWord);
+ // uint64_t xi = *xip++
+ __ ldr(R2, Address(R4, 2*Bigint::kBytesPerDigit, Address::PostIndex));
- // uint32_t aj = *ajp
- __ ldr(R1, Address(R5, 0), kUnsignedWord);
-
- // uint96_t t = R1:R0 = 2*x*xi + aj + c
- __ umaddl(R0, R2, R3, ZR); // X0 = W2*W3 + 0 = x*xi.
- __ add(R1, R0, Operand(R1)); // R1 = x*xi + aj.
- __ adds(R0, R0, Operand(R1));
- __ adc(R1, ZR, ZR); // R1:R0 = 2*R0 + R1 = 2*x*xi + aj.
+ // uint192_t t = R2:R1:R0 = 2*x*xi + aj + c
+ __ mul(R0, R2, R3); // R0 = low64(R2*R3) = low64(x*xi).
+ __ umulh(R1, R2, R3); // R1 = high64(R2*R3) = high64(x*xi).
+ __ adds(R0, R0, Operand(R0));
+ __ adcs(R1, R1, R1);
+ __ adc(R2, ZR, ZR); // R2:R1:R0 = R1:R0 + R1:R0 = 2*x*xi.
__ adds(R0, R0, Operand(R6));
- __ adc(R1, R1, ZR); // R1:R0 = R1:R0 + R6 = 2*x*xi + aj + c.
+ __ adcs(R1, R1, R7);
+ __ adc(R2, R2, ZR); // R2:R1:R0 += c.
+ __ ldr(R7, Address(R5, 0)); // R7 = aj = *ajp.
+ __ adds(R0, R0, Operand(R7));
+ __ adcs(R6, R1, ZR);
+ __ adc(R7, R2, ZR); // R7:R6:R0 = 2*x*xi + aj + c.
- // *ajp++ = low32(t) = R0
- __ str(R0, Address(R5, Bigint::kBytesPerDigit, Address::PostIndex),
- kUnsignedWord);
+ // *ajp++ = low64(t) = R0
+ __ str(R0, Address(R5, 2*Bigint::kBytesPerDigit, Address::PostIndex));
- // R6 = c = t >> 32.
- __ LslImmediate(R6, R1, 32);
- __ orr(R6, R6, Operand(R0, LSR, 32));
-
// while (--n >= 0)
__ subs(R8, R8, Operand(1)); // --n
__ b(&loop, PL);
__ Bind(&done);
- // uint32_t aj = *ajp
- __ ldr(R0, Address(R5, 0), kUnsignedWord);
+ // uint64_t aj = *ajp
+ __ ldr(R0, Address(R5, 0));
- // uint64_t t = aj + c
- __ add(R6, R6, Operand(R0));
+ // uint128_t t = aj + c
+ __ adds(R6, R6, Operand(R0));
+ __ adc(R7, R7, ZR);
- // R7 = R6 >> 32.
- __ LsrImmediate(R7, R6, 32);
+ // *ajp = low64(t) = R6
+ // *(ajp + 1) = high64(t) = R7
+ __ stp(R6, R7, Address(R5, 0, Address::PairOffset));
- // *ajp = low32(t) = low32(R6)
- // *(ajp + 1) = high32(t) = low32(R7)
- __ stp(R6, R7, Address(R5, 0, Address::PairOffset), kUnsignedWord);
-
__ Bind(&x_zero);
- __ LoadImmediate(R0, Smi::RawValue(1), kNoPP); // One digit processed.
+ __ LoadImmediate(R0, Smi::RawValue(2), kNoPP); // Two digits processed.
__ ret();
}
void Intrinsifier::Bigint_estQuotientDigit(Assembler* assembler) {
+ // There is no 128-bit by 64-bit division instruction on arm64, so we use two
+ // 64-bit by 32-bit divisions and two 64-bit by 64-bit multiplications to
+ // adjust the two 32-bit digits of the estimated quotient.
+ //
// Pseudo code:
// static int _estQuotientDigit(Uint32List args, Uint32List digits, int i) {
- // uint32_t yt = args[_YT]; // _YT == 1.
- // uint32_t* dp = &digits[i >> 1]; // i is Smi.
- // uint32_t dh = dp[0]; // dh == digits[i >> 1].
- // uint32_t qd;
+ // uint64_t yt = args[_YT_LO .. _YT]; // _YT_LO == 0, _YT == 1.
+ // uint64_t* dp = &digits[(i >> 1) - 1]; // i is Smi.
+ // uint64_t dh = dp[0]; // dh == digits[(i >> 1) - 1 .. i >> 1].
+ // uint64_t qd;
// if (dh == yt) {
- // qd = DIGIT_MASK;
+ // qd = (DIGIT_MASK << 32) | DIGIT_MASK;
// } else {
- // dl = dp[-1]; // dl == digits[(i - 1) >> 1].
- // qd = dh:dl / yt; // No overflow possible, because dh < yt.
+ // dl = dp[-1]; // dl == digits[(i >> 1) - 3 .. (i >> 1) - 2].
+ // // We cannot calculate qd = dh:dl / yt, so ...
+ // uint64_t yth = yt >> 32;
+ // uint64_t qh = dh / yth;
+ // uint128_t ph:pl = yt*qh;
+ // uint64_t tl = (dh << 32)|(dl >> 32);
+ // uint64_t th = dh >> 32;
+ // while ((ph > th) || ((ph == th) && (pl > tl))) {
+ // if (pl < yt) --ph;
+ // pl -= yt;
+ // --qh;
+ // }
+ // qd = qh << 32;
+ // tl = (pl << 32);
+ // th = (ph << 32)|(pl >> 32);
+ // if (tl > dl) ++th;
+ // dl -= tl;
+ // dh -= th;
+ // uint64_t ql = ((dh << 32)|(dl >> 32)) / yth;
+ // ph:pl = yt*ql;
+ // while ((ph > dh) || ((ph == dh) && (pl > dl))) {
+ // if (pl < yt) --ph;
+ // pl -= yt;
+ // --ql;
+ // }
+ // qd |= ql;
// }
- // args[_QD] = qd; // _QD == 2.
- // return 1;
+ // args[_QD .. _QD_HI] = qd; // _QD == 2, _QD_HI == 3.
+ // return 2;
// }
// R4 = args
__ ldr(R4, Address(SP, 2 * kWordSize)); // args
- // R3 = yt = args[1]
- __ ldr(R3, FieldAddress(R4,
- TypedData::data_offset() + Bigint::kBytesPerDigit),
- kUnsignedWord);
+ // R3 = yt = args[0..1]
+ __ ldr(R3, FieldAddress(R4, TypedData::data_offset()));
- // R2 = dh = digits[i >> 1]
+ // R2 = dh = digits[(i >> 1) - 1 .. i >> 1]
// R0 = i as Smi, R1 = digits
__ ldp(R0, R1, Address(SP, 0 * kWordSize, Address::PairOffset));
__ add(R1, R1, Operand(R0, LSL, 1));
- __ ldr(R2, FieldAddress(R1, TypedData::data_offset()), kUnsignedWord);
+ __ ldr(R2,
+ FieldAddress(R1, TypedData::data_offset() - Bigint::kBytesPerDigit));
- // R0 = qd = DIGIT_MASK = -1
+ // R0 = qd = (DIGIT_MASK << 32) | DIGIT_MASK = -1
__ movn(R0, Immediate(0), 0);
// Return qd if dh == yt
@@ -1196,24 +1218,110 @@
__ cmp(R2, Operand(R3));
__ b(&return_qd, EQ);
- // R1 = dl = digits[(i - 1) >> 1]
+ // R1 = dl = digits[(i >> 1) - 3 .. (i >> 1) - 2]
__ ldr(R1,
- FieldAddress(R1, TypedData::data_offset() - Bigint::kBytesPerDigit),
- kUnsignedWord);
+ FieldAddress(R1, TypedData::data_offset() - 3*Bigint::kBytesPerDigit));
- // R1 = dh:dl
- __ orr(R1, R1, Operand(R2, LSL, 32));
+ // R5 = yth = yt >> 32
+ __ orr(R5, ZR, Operand(R3, LSR, 32));
- // R0 = qd = dh:dl / yt = R1 / R3
- __ udiv(R0, R1, R3);
+ // R6 = qh = dh / yth
+ __ udiv(R6, R2, R5);
+ // R8:R7 = ph:pl = yt*qh
+ __ mul(R7, R3, R6);
+ __ umulh(R8, R3, R6);
+
+ // R9 = tl = (dh << 32)|(dl >> 32)
+ __ orr(R9, ZR, Operand(R2, LSL, 32));
+ __ orr(R9, R9, Operand(R1, LSR, 32));
+
+ // R10 = th = dh >> 32
+ __ orr(R10, ZR, Operand(R2, LSR, 32));
+
+ // while ((ph > th) || ((ph == th) && (pl > tl)))
+ Label qh_adj_loop, qh_adj, qh_ok;
+ __ Bind(&qh_adj_loop);
+ __ cmp(R8, Operand(R10));
+ __ b(&qh_adj, HI);
+ __ b(&qh_ok, NE);
+ __ cmp(R7, Operand(R9));
+ __ b(&qh_ok, LS);
+
+ __ Bind(&qh_adj);
+ // if (pl < yt) --ph
+ __ sub(TMP, R8, Operand(1)); // TMP = ph - 1
+ __ cmp(R7, Operand(R3));
+ __ csel(R8, TMP, R8, CC); // R8 = R7 < R3 ? TMP : R8
+
+ // pl -= yt
+ __ sub(R7, R7, Operand(R3));
+
+ // --qh
+ __ sub(R6, R6, Operand(1));
+
+ __ Bind(&qh_ok);
+ // R0 = qd = qh << 32
+ __ orr(R0, ZR, Operand(R6, LSL, 32));
+
+ // tl = (pl << 32)
+ __ orr(R9, ZR, Operand(R7, LSL, 32));
+
+ // th = (ph << 32)|(pl >> 32);
+ __ orr(R10, ZR, Operand(R8, LSL, 32));
+ __ orr(R10, R10, Operand(R7, LSR, 32));
+
+ // if (tl > dl) ++th
+ __ add(TMP, R10, Operand(1)); // TMP = th + 1
+ __ cmp(R9, Operand(R1));
+ __ csel(R10, TMP, R10, HI); // R10 = R9 > R1 ? TMP : R10
+
+ // dl -= tl
+ __ sub(R1, R1, Operand(R9));
+
+ // dh -= th
+ __ sub(R2, R2, Operand(R10));
+
+ // R6 = ql = ((dh << 32)|(dl >> 32)) / yth
+ __ orr(R6, ZR, Operand(R2, LSL, 32));
+ __ orr(R6, R6, Operand(R1, LSR, 32));
+ __ udiv(R6, R6, R5);
+
+ // R8:R7 = ph:pl = yt*ql
+ __ mul(R7, R3, R6);
+ __ umulh(R8, R3, R6);
+
+ // while ((ph > dh) || ((ph == dh) && (pl > dl))) {
+ Label ql_adj_loop, ql_adj, ql_ok;
+ __ Bind(&ql_adj_loop);
+ __ cmp(R8, Operand(R2));
+ __ b(&ql_adj, HI);
+ __ b(&ql_ok, NE);
+ __ cmp(R7, Operand(R1));
+ __ b(&ql_ok, LS);
+
+ __ Bind(&ql_adj);
+ // if (pl < yt) --ph
+ __ sub(TMP, R8, Operand(1)); // TMP = ph - 1
+ __ cmp(R7, Operand(R3));
+ __ csel(R8, TMP, R8, CC); // R8 = R7 < R3 ? TMP : R8
+
+ // pl -= yt
+ __ sub(R7, R7, Operand(R3));
+
+ // --ql
+ __ sub(R6, R6, Operand(1));
+
+ __ Bind(&ql_ok);
+ // qd |= ql;
+ __ orr(R0, R0, Operand(R6));
+
__ Bind(&return_qd);
- // args[2] = qd
+ // args[2..3] = qd
__ str(R0,
- FieldAddress(R4, TypedData::data_offset() + 2*Bigint::kBytesPerDigit),
- kUnsignedWord);
+ FieldAddress(R4, TypedData::data_offset() + 2*Bigint::kBytesPerDigit));
- __ LoadImmediate(R0, Smi::RawValue(1), kNoPP); // One digit processed.
+ __ LoadImmediate(R0, Smi::RawValue(2), kNoPP); // Two digits processed.
__ ret();
}
@@ -1221,37 +1329,34 @@
void Intrinsifier::Montgomery_mulMod(Assembler* assembler) {
// Pseudo code:
// static int _mulMod(Uint32List args, Uint32List digits, int i) {
- // uint32_t rho = args[_RHO]; // _RHO == 2.
- // uint32_t d = digits[i >> 1]; // i is Smi.
- // uint64_t t = rho*d;
- // args[_MU] = t mod DIGIT_BASE; // _MU == 4.
- // args[_MU_HI] = 0; // _MU_HI == 3.
- // return 1;
+ // uint64_t rho = args[_RHO .. _RHO_HI]; // _RHO == 2, _RHO_HI == 3.
+ // uint64_t d = digits[i >> 1 .. (i >> 1) + 1]; // i is Smi and even.
+ // uint128_t t = rho*d;
+ // args[_MU .. _MU_HI] = t mod DIGIT_BASE^2; // _MU == 4, _MU_HI == 5.
+ // return 2;
// }
// R4 = args
__ ldr(R4, Address(SP, 2 * kWordSize)); // args
- // R3 = rho = args[2]
+ // R3 = rho = args[2..3]
__ ldr(R3,
- FieldAddress(R4, TypedData::data_offset() + 2*Bigint::kBytesPerDigit),
- kUnsignedWord);
+ FieldAddress(R4, TypedData::data_offset() + 2*Bigint::kBytesPerDigit));
- // R2 = digits[i >> 1]
+ // R2 = digits[i >> 1 .. (i >> 1) + 1]
// R0 = i as Smi, R1 = digits
__ ldp(R0, R1, Address(SP, 0 * kWordSize, Address::PairOffset));
__ add(R1, R1, Operand(R0, LSL, 1));
- __ ldr(R2, FieldAddress(R1, TypedData::data_offset()), kUnsignedWord);
+ __ ldr(R2, FieldAddress(R1, TypedData::data_offset()));
- // X0 = t = rho*d
- __ umaddl(R0, R2, R3, ZR); // X0 = W2*W3 + 0.
+ // R0 = rho*d mod DIGIT_BASE
+ __ mul(R0, R2, R3); // R0 = low64(R2*R3).
- // args[4] = t mod DIGIT_BASE = low32(t)
+ // args[4 .. 5] = R0
__ str(R0,
- FieldAddress(R4, TypedData::data_offset() + 4*Bigint::kBytesPerDigit),
- kUnsignedWord);
+ FieldAddress(R4, TypedData::data_offset() + 4*Bigint::kBytesPerDigit));
- __ LoadImmediate(R0, Smi::RawValue(1), kNoPP); // One digit processed.
+ __ LoadImmediate(R0, Smi::RawValue(2), kNoPP); // Two digits processed.
__ ret();
}
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