mirror of
https://github.com/golang/go
synced 2024-11-07 14:56:16 -07:00
c19759aa48
This function is no longer used. Eliminating this actually fixes several problems: - It made assumptions about what registers memclrNoHeapPointers would preserve. Besides being an abstraction violation and lurking maintenance issue, this actively became a problem for regabi because the call to memclrNoHeapPointers now happens through an ABI wrapper, which is generated by the compiler and hence we can't easily control what registers it clobbers. - The amd64 implementation (at least), does not interact with the host ABI correctly. Notably, it doesn't save many of the registers that are callee-save in the host ABI but caller-save in the Go ABI. - It interacts strangely with the NOSPLIT checker because it allocates an entire M and G on its stack. It worked around this on arm64, and happened to do things the NOSPLIT checker couldn't track on 386 and amd64, and happened to be *4 bytes* below the limit on arm (so any addition to the m or g structs would cause a NOSPLIT failure). See CL 309031 for a more complete explanation. Fixes #45530. Updates #40724. Change-Id: Ic70d4d7e1c17f1d796575b3377b8529449e93576 Reviewed-on: https://go-review.googlesource.com/c/go/+/309634 Trust: Austin Clements <austin@google.com> Run-TryBot: Austin Clements <austin@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Michael Pratt <mpratt@google.com> Reviewed-by: Michael Knyszek <mknyszek@google.com>
137 lines
2.4 KiB
ArmAsm
137 lines
2.4 KiB
ArmAsm
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build !plan9
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#include "go_asm.h"
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#include "textflag.h"
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// See memclrNoHeapPointers Go doc for important implementation constraints.
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// func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr)
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TEXT runtime·memclrNoHeapPointers(SB), NOSPLIT, $0-8
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MOVL ptr+0(FP), DI
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MOVL n+4(FP), BX
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XORL AX, AX
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// MOVOU seems always faster than REP STOSL.
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tail:
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// BSR+branch table make almost all memmove/memclr benchmarks worse. Not worth doing.
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TESTL BX, BX
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JEQ _0
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CMPL BX, $2
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JBE _1or2
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CMPL BX, $4
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JB _3
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JE _4
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CMPL BX, $8
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JBE _5through8
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CMPL BX, $16
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JBE _9through16
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CMPB internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1
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JNE nosse2
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PXOR X0, X0
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CMPL BX, $32
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JBE _17through32
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CMPL BX, $64
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JBE _33through64
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CMPL BX, $128
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JBE _65through128
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CMPL BX, $256
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JBE _129through256
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loop:
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MOVOU X0, 0(DI)
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MOVOU X0, 16(DI)
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MOVOU X0, 32(DI)
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MOVOU X0, 48(DI)
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MOVOU X0, 64(DI)
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MOVOU X0, 80(DI)
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MOVOU X0, 96(DI)
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MOVOU X0, 112(DI)
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MOVOU X0, 128(DI)
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MOVOU X0, 144(DI)
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MOVOU X0, 160(DI)
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MOVOU X0, 176(DI)
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MOVOU X0, 192(DI)
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MOVOU X0, 208(DI)
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MOVOU X0, 224(DI)
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MOVOU X0, 240(DI)
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SUBL $256, BX
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ADDL $256, DI
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CMPL BX, $256
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JAE loop
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JMP tail
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_1or2:
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MOVB AX, (DI)
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MOVB AX, -1(DI)(BX*1)
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RET
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_0:
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RET
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_3:
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MOVW AX, (DI)
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MOVB AX, 2(DI)
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RET
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_4:
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// We need a separate case for 4 to make sure we clear pointers atomically.
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MOVL AX, (DI)
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RET
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_5through8:
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MOVL AX, (DI)
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MOVL AX, -4(DI)(BX*1)
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RET
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_9through16:
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MOVL AX, (DI)
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MOVL AX, 4(DI)
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MOVL AX, -8(DI)(BX*1)
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MOVL AX, -4(DI)(BX*1)
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RET
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_17through32:
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MOVOU X0, (DI)
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MOVOU X0, -16(DI)(BX*1)
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RET
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_33through64:
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MOVOU X0, (DI)
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MOVOU X0, 16(DI)
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MOVOU X0, -32(DI)(BX*1)
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MOVOU X0, -16(DI)(BX*1)
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RET
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_65through128:
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MOVOU X0, (DI)
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MOVOU X0, 16(DI)
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MOVOU X0, 32(DI)
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MOVOU X0, 48(DI)
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MOVOU X0, -64(DI)(BX*1)
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MOVOU X0, -48(DI)(BX*1)
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MOVOU X0, -32(DI)(BX*1)
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MOVOU X0, -16(DI)(BX*1)
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RET
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_129through256:
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MOVOU X0, (DI)
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MOVOU X0, 16(DI)
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MOVOU X0, 32(DI)
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MOVOU X0, 48(DI)
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MOVOU X0, 64(DI)
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MOVOU X0, 80(DI)
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MOVOU X0, 96(DI)
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MOVOU X0, 112(DI)
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MOVOU X0, -128(DI)(BX*1)
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MOVOU X0, -112(DI)(BX*1)
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MOVOU X0, -96(DI)(BX*1)
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MOVOU X0, -80(DI)(BX*1)
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MOVOU X0, -64(DI)(BX*1)
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MOVOU X0, -48(DI)(BX*1)
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MOVOU X0, -32(DI)(BX*1)
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MOVOU X0, -16(DI)(BX*1)
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RET
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nosse2:
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MOVL BX, CX
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SHRL $2, CX
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REP
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STOSL
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ANDL $3, BX
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JNE tail
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RET
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