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1 // Copyright 2012 the V8 project authors. All rights reserved. | 1 // Copyright 2012 the V8 project authors. All rights reserved. |
2 // Redistribution and use in source and binary forms, with or without | 2 // Redistribution and use in source and binary forms, with or without |
3 // modification, are permitted provided that the following conditions are | 3 // modification, are permitted provided that the following conditions are |
4 // met: | 4 // met: |
5 // | 5 // |
6 // * Redistributions of source code must retain the above copyright | 6 // * Redistributions of source code must retain the above copyright |
7 // notice, this list of conditions and the following disclaimer. | 7 // notice, this list of conditions and the following disclaimer. |
8 // * Redistributions in binary form must reproduce the above | 8 // * Redistributions in binary form must reproduce the above |
9 // copyright notice, this list of conditions and the following | 9 // copyright notice, this list of conditions and the following |
10 // disclaimer in the documentation and/or other materials provided | 10 // disclaimer in the documentation and/or other materials provided |
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1378 | 1378 |
1379 // Theoretically, a variation of the branch-free code for integer division by | 1379 // Theoretically, a variation of the branch-free code for integer division by |
1380 // a power of 2 (calculating the remainder via an additional multiplication | 1380 // a power of 2 (calculating the remainder via an additional multiplication |
1381 // (which gets simplified to an 'and') and subtraction) should be faster, and | 1381 // (which gets simplified to an 'and') and subtraction) should be faster, and |
1382 // this is exactly what GCC and clang emit. Nevertheless, benchmarks seem to | 1382 // this is exactly what GCC and clang emit. Nevertheless, benchmarks seem to |
1383 // indicate that positive dividends are heavily favored, so the branching | 1383 // indicate that positive dividends are heavily favored, so the branching |
1384 // version performs better. | 1384 // version performs better. |
1385 HMod* hmod = instr->hydrogen(); | 1385 HMod* hmod = instr->hydrogen(); |
1386 int32_t mask = divisor < 0 ? -(divisor + 1) : (divisor - 1); | 1386 int32_t mask = divisor < 0 ? -(divisor + 1) : (divisor - 1); |
1387 Label dividend_is_not_negative, done; | 1387 Label dividend_is_not_negative, done; |
1388 if (hmod->left()->CanBeNegative()) { | 1388 if (hmod->CheckFlag(HValue::kLeftCanBeNegative)) { |
1389 __ test(dividend, dividend); | 1389 __ test(dividend, dividend); |
1390 __ j(not_sign, ÷nd_is_not_negative, Label::kNear); | 1390 __ j(not_sign, ÷nd_is_not_negative, Label::kNear); |
1391 // Note that this is correct even for kMinInt operands. | 1391 // Note that this is correct even for kMinInt operands. |
1392 __ neg(dividend); | 1392 __ neg(dividend); |
1393 __ and_(dividend, mask); | 1393 __ and_(dividend, mask); |
1394 __ neg(dividend); | 1394 __ neg(dividend); |
1395 if (hmod->CheckFlag(HValue::kBailoutOnMinusZero)) { | 1395 if (hmod->CheckFlag(HValue::kBailoutOnMinusZero)) { |
1396 DeoptimizeIf(zero, instr->environment()); | 1396 DeoptimizeIf(zero, instr->environment()); |
1397 } | 1397 } |
1398 __ jmp(&done, Label::kNear); | 1398 __ jmp(&done, Label::kNear); |
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6331 FixedArray::kHeaderSize - kPointerSize)); | 6331 FixedArray::kHeaderSize - kPointerSize)); |
6332 __ bind(&done); | 6332 __ bind(&done); |
6333 } | 6333 } |
6334 | 6334 |
6335 | 6335 |
6336 #undef __ | 6336 #undef __ |
6337 | 6337 |
6338 } } // namespace v8::internal | 6338 } } // namespace v8::internal |
6339 | 6339 |
6340 #endif // V8_TARGET_ARCH_IA32 | 6340 #endif // V8_TARGET_ARCH_IA32 |
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