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cmd/internal/obj/mips: assembler panic when assemble neg instruction #23548

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crvv opened this issue Jan 25, 2018 · 2 comments
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cmd/internal/obj/mips: assembler panic when assemble neg instruction #23548

crvv opened this issue Jan 25, 2018 · 2 comments
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@crvv
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crvv commented Jan 25, 2018 •
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What version of Go are you using (go version)?

1.9.3 and tip(1b69d19)

What did you do?

Create the following file.
Run GOARCH=mips GOOS=linux go tool asm asm.s or GOARCH=mips64 GOOS=linux go tool asm asm.s

asm.s

TEXT ·a(SB),0,$0
    NEGW R1, R1
    RET

What did you expect to see?

Success or a failure without panic.

What did you see instead?

$ GOARCH=mips64 GOOS=linux go tool asm asm.s
# package/path
asm: illegal combination NEGW REG NONE REG
00000 (./asm.s:2)	NEGW	R1, R1
asm: illegal combination NEGW REG NONE REG
00000 (./asm.s:2)	NEGW	R1, R1
asm: illegal combination NEGW REG NONE REG
00000 (./asm.s:2)	NEGW	R1, R1
asm: bad irr opcode NEGW
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0xa0 pc=0x10ec707]

goroutine 1 [running]:
cmd/internal/obj/mips.(*ctxt0).asmout(0xc420055bc8, 0xc420093380, 0x127e940, 0xc420055b60, 0x4, 0x4)
	$GOROOT/src/cmd/internal/obj/mips/asm0.go:1237 +0xac7
cmd/internal/obj/mips.span0(0xc4200bc000, 0xc4200c6000, 0xc42005e3c0)
	$GOROOT/src/cmd/internal/obj/mips/asm0.go:500 +0x7c8
cmd/internal/obj.Flushplist(0xc4200bc000, 0xc420055e50, 0xc42005e3c0, 0x0, 0x0)
	$GOROOT/src/cmd/internal/obj/plist.go:107 +0x6ca
main.main()
	$GOROOT/src/cmd/asm/main.go:75 +0x543
@crvv crvv changed the title cmd/internal/obj/mips: compiler panic when assemble neg instruction cmd/internal/obj/mips: assembler panic when assemble neg instruction Jan 25, 2018
@cherrymui
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It doesn't support NEGW instruction. You should do SUBVU R1, R0, R1 on MIPS64 or SUBU R1, R0, R1 on MIPS32.

We should remove NEGW from instruction list.

@cherrymui cherrymui self-assigned this Jan 25, 2018
@gopherbot
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Change https://golang.org/cl/89896 mentions this issue: cmd/internal/obj/mips: remove NEGW, avoid crash with illegal instruction

@golang golang locked and limited conversation to collaborators Feb 14, 2019
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@crvv @gopherbot @cherrymui