45 lines
1.2 KiB
ArmAsm
45 lines
1.2 KiB
ArmAsm
// Copyright 2018 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "textflag.h"
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// Documentation is available in parameters.go.
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//
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// func muldiv64(value, multiplier, divisor uint64) (uint64, bool)
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TEXT ·muldiv64(SB),NOSPLIT,$0-33
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MOVQ value+0(FP), AX
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MOVQ multiplier+8(FP), BX
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MOVQ divisor+16(FP), CX
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// Multiply AX*BX and store result in DX:AX.
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MULQ BX
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// If divisor <= (value*multiplier) / 2^64, then the division will overflow.
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//
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// (value*multiplier) / 2^64 is DX:AX >> 64, or simply DX.
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CMPQ CX, DX
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JLE overflow
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// Divide DX:AX by CX.
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DIVQ CX
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MOVQ AX, result+24(FP)
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MOVB $1, ok+32(FP)
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RET
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overflow:
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MOVQ $0, result+24(FP)
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MOVB $0, ok+32(FP)
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RET
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