44 lines
1.7 KiB
ArmAsm
44 lines
1.7 KiB
ArmAsm
// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
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// SPDX-License-Identifier: BSD-3-Clause
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#include "textflag.h"
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// ABI0 JIT trampoline for arm64.
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//
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// enterJIT saves the Go SP and LR, switches to the prepared stack, and
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// branches to the JIT function. When the function RETs (BR LR), control
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// lands in leaveJIT, which restores the Go stack and returns.
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//
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// The prepared stack layout:
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// [0] leaveJIT address (loaded into LR before jumping to fn)
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// [8] ABI0 argument area
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// func enterJIT(fn uintptr, stack uintptr)
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TEXT ·enterJIT(SB), NOSPLIT, $0-16
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MOVD fn+0(FP), R0 // target function address
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MOVD R30, savedLR(SB) // save link register
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MOVD R3, savedSP(SB) // save Go stack pointer
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MOVD stack+8(FP), R3 // load prepared stack pointer
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MOVD 0(R3), R30 // load leaveJIT address into LR
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ADD $8, R3, R3 // advance past return address
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MOVD R3, RSP // switch to prepared stack
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JMP (R0) // branch to JIT function
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// func leaveJIT()
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TEXT ·leaveJIT(SB), NOSPLIT, $0-0
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MOVD savedSP(SB), R3 // restore Go stack pointer
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MOVD R3, RSP
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MOVD savedLR(SB), R30 // restore link register
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RET // return to Go caller
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// leaveRawAddr holds the raw .abi0 address of leaveJIT, read by call_arm64.go
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// in preference to reflect.ValueOf(leaveJIT), which returns the address of the
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// ABIInternal wrapper the linker interposes: the wrapper's prologue clobbers
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// the saved-register window the JIT call depends on.
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GLOBL ·leaveRawAddr(SB), NOPTR, $8
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DATA ·leaveRawAddr(SB)/8, $·leaveJIT(SB)
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// Package-level storage for saved registers.
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GLOBL savedLR(SB), NOPTR, $8
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GLOBL savedSP(SB), NOPTR, $8
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