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https://github.com/tinygo-org/tinygo.git
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Ayke van Laethem
3b8062170c
Previously the assembler was reordering this code:
jal tinygo_scanstack
move $a0, $sp
Into this:
jal tinygo_scanstack
nop
move $a0, $sp
So it was "helpfully" inserting a branch delay slot, even though this
was already being taken care of.
Somehow this didn't break, but it does break in the WIP threading branch
(https://github.com/tinygo-org/tinygo/pull/4559) where this bug leads to
a crash.
45 lines
1.1 KiB
ArmAsm
45 lines
1.1 KiB
ArmAsm
// Do not reorder instructions to insert a branch delay slot.
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// We know what we're doing, and will manually fill the branch delay slot.
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.set noreorder
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.section .text.tinygo_scanCurrentStack
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.global tinygo_scanCurrentStack
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.type tinygo_scanCurrentStack, %function
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tinygo_scanCurrentStack:
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// Push callee-saved registers onto the stack.
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addiu $sp, $sp, -40
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sw $ra, 36($sp)
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sw $s8, 32($sp)
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sw $s7, 28($sp)
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sw $s6, 24($sp)
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sw $s5, 20($sp)
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sw $s4, 16($sp)
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sw $s3, 12($sp)
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sw $s2, 8($sp)
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sw $s1, 4($sp)
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sw $s0, ($sp)
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// Scan the stack.
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jal tinygo_scanstack
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move $a0, $sp // in the branch delay slot
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// Restore return address.
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lw $ra, 36($sp)
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// Restore stack state.
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addiu $sp, $sp, 40
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// Return to the caller.
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jalr $ra
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nop
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.section .text.tinygo_longjmp
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.global tinygo_longjmp
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tinygo_longjmp:
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// Note: the code we jump to assumes a0 is non-zero, which is already the
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// case because that's the defer frame pointer.
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lw $sp, 0($a0) // jumpSP
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lw $a1, 4($a0) // jumpPC
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jr $a1
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nop
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