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cmd/objdump: can not disassemble ARM DIVUHW / DIVHW #20096

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benshi001 opened this issue Apr 24, 2017 · 12 comments
Closed

cmd/objdump: can not disassemble ARM DIVUHW / DIVHW #20096

benshi001 opened this issue Apr 24, 2017 · 12 comments
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FrozenDueToAge help wanted NeedsFix The path to resolution is known, but the work has not been done.
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Go1.9Maybe

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@benshi001
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benshi001 commented Apr 24, 2017 •
edited

Wtih a simple test file arm.s
TEXT foo(SB), 4, $0
DIVHW R0, R1, R2
DIVUHW R0, R1, R2
DIVHW R0, R1
DIVUHW R0, R1
ADD $ 0xfff9, R0
END

Here are what I do and the results,
pi@raspberrypi:~ $ cat arm.s
TEXT foo(SB), 4, $0
DIVHW R0, R1, R2
DIVUHW R0, R1, R2
DIVHW R0, R1
DIVUHW R0, R1
ADD $ 0xfff9, R0
END
pi@raspberrypi:~ $ GOROOT= ~ /go PATH=$GOROOT/bin:$PATH go tool asm arm.s
pi@raspberrypi:~ $ GOROOT= ~ /go PATH=$GOROOT/bin:$PATH go tool objdump arm.o
TEXT foo(SB) gofile../home/pi/arm.s
arm.s:4 0x85 e712f011 ?
arm.s:5 0x89 e732f011 ?
arm.s:7 0x8d e711f011 ?
arm.s:8 0x91 e731f011 ?
arm.s:10 0x95 e30fbff9 MOVW $65529, R11
arm.s:10 0x99 e080000b ADD R11, R0, R0

The DIVHW/DIVUHW are not disassembled .
@bradfitz bradfitz changed the title src/cmd/objdump: can not disassemble DIVUHW / DIVHW cmd/objdump: can not disassemble DIVUHW / DIVHW Apr 24, 2017
@bradfitz bradfitz changed the title cmd/objdump: can not disassemble DIVUHW / DIVHW cmd/objdump: can not disassemble ARM DIVUHW / DIVHW Apr 24, 2017
@bradfitz bradfitz added this to the Go1.9Maybe milestone Apr 24, 2017
@bradfitz bradfitz added help wanted NeedsFix The path to resolution is known, but the work has not been done. labels Apr 24, 2017
@cherrymui
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The disassembler comes from x/arch subrepo (https://go.googlesource.com/arch), which contains a table generated by parsing the PDF of the hardware manual. It looks like these instructions are not in the table.

@benshi001 would you like to update the table with a newer version of the manual that includes these instructions? (I don't have one.)

@benshi001
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OK. I will do it later. Thank you.

@benshi001
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Questions,

  1. https://github.com/golang/go/tree/master/src/cmd/vendor/golang.org/x/arch/arm/armasm is much older than https://github.com/golang/arch/tree/master/, which one should I follow?
  2. Which tool is used to generate arm.csv? Or I have to edit it by hand?
  3. Any more instructions ?

@benshi001
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arm.csv.zip

  1. I checked the newest arm manual against the arm.csv, UDIV/SDIV/UDF are new added, and others are not used by go. (Such as VCLZ is SIMD, CHKA is ThumbEE)

  2. I added UDIV/SDIV/UDF to the attached arm.csv and got tables.go by "go run ../armmap/map.go -fmt=decoder ../arm.csv >_tables.go && gofmt _tables.go >tables.go && rm _tables.go".

  3. I committed https://go-review.googlesource.com/c/41890/, now DIVHW and DIVUHW can be disassembled correctly.

// DIVHW R0, R1, R2: R1 / R0 -> R2
DIVHW R0, R1, R2 // 11f012e7
DIVUHW R0, R1, R2 // 11f032e7
// DIVHW R0, R1: R1 / R0 -> R1
DIVHW R0, R1 // 11f011e7
DIVUHW R0, R1 // 11f031e7

arm.s:8 0x8f e712f011 SDIV R0, R1, R2
arm.s:9 0x93 e732f011 UDIV R0, R1, R2
arm.s:11 0x97 e711f011 SDIV R0, R1, R1
arm.s:12 0x9b e731f011 UDIV R0, R1, R1

@benshi001
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The UDF is not supported by the assembler, so it is not tested.

@benshi001
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A bug is found,

"MULS R1, R2, R3, R4" is dissambled to "MLS R3, R1, R2, R4", which should be "MLS R1, R2, R3, R4"

Patch set 3 of CL https://go-review.googlesource.com/#/c/41891/ fixes it.

@gopherbot
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CL https://golang.org/cl/42171 mentions this issue.

@benshi001
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https://go-review.googlesource.com/#/c/41891/ fixes the DIV/DIVU issue.
https://go-review.googlesource.com/#/c/42171/ fixes the MLA issue.

@benshi001
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QADD is also not decoded correctly.

0xe1086055 should be decoded to "QADD R6, R8, R5" in GNU syntax, but actually "QADD R6, R5, R8".

@benshi001
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There same error of wrong register list also exists in QDADD/QSUB

@benshi001
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fixed in https://go-review.googlesource.com/c/41891/

@gopherbot
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Change https://golang.org/cl/49530 mentions this issue: cmd/vendor/golang.org/x/arch: pull updates from x repo

gopherbot pushed a commit that referenced this issue Aug 16, 2017
@cherrymui
cmd/vendor/golang.org/x/arch: pull updates from x repo
56b62c7 
Vendor from golang.org/x/arch (commit f185940).

Implements #19157

Updates #12840
Updates #20762
Updates #20897
Updates #20096
Updates #20766
Updates #20752
Updates #20096
Updates #19142

Change-Id: Idefb8ba2c355dc07f3b9e8dcf5f00173256a0f0f
Reviewed-on: https://go-review.googlesource.com/49530
Reviewed-by: Cherry Zhang <cherryyz@google.com>
@golang golang locked and limited conversation to collaborators Jul 27, 2018
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