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cmd/asm: arm64 assembler rejects "MOVK $(33825<<48), R2" #52261

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ericlagergren opened this issue Apr 10, 2022 · 2 comments
Closed

cmd/asm: arm64 assembler rejects "MOVK $(33825<<48), R2" #52261

ericlagergren opened this issue Apr 10, 2022 · 2 comments
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@ericlagergren
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ericlagergren commented Apr 10, 2022 •
edited

What version of Go are you using (go version)?

$ go version
go version go1.18 darwin/arm64

Does this issue reproduce with the latest release?

This is the latest release.

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GO111MODULE=""
GOARCH="arm64"
GOBIN="/Users/eric/gopath/bin"
GOCACHE="/Users/eric/Library/Caches/go-build"
GOENV="/Users/eric/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/eric/gopath/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/eric/gopath"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_arm64"
GOVCS=""
GOVERSION="go1.18"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/eric/git/polyval/go.mod"
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/2f/2_yz21b92h94_pvr2m00gzh80000gn/T/go-build2162191990=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Wrote an assembly program with MOVK $(33825<<48), R5.

(The instruction was taken from Clang generating movk x5, #33825, lsl #48.)

What did you expect to see?

It compile.

What did you see instead?

asm: requires uimm16
00096 (/Users/eric/git/polyval/polyval_arm64.s:451)	MOVK	$-8925852986471612416, R5
asm: assembly failed
@ericlagergren ericlagergren changed the title cmd/asm: rejects "MOVK $(33825<<48), R2" cmd/asm: arm64 assembler rejects "MOVK $(33825<<48), R2" Apr 10, 2022
@ericlagergren
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ericlagergren commented Apr 10, 2022 •
edited

The MOVK instruction was part of the hand-written sequence:

MOVD  $8456, R5
MOVK  $(4228<<16), R5
MOVK  $(2114<<32), R5
MOVK  $(33825<<48), R5

Interestingly, when I replace those instructions with

MOVD $0x8421084210842108, R5

the compiler actually emits the instruction that cmd/asm rejects:

$ go tool objdump -gnu -s ctmulAsm ./polyval.test
MOVD $8456, R5                       // mov x5, #0x2108
MOVK $(4228<<16), R5                 // movk x5, #0x1084, lsl #16
MOVK $(2114<<32), R5                 // movk x5, #0x842, lsl #32
MOVK $(33825<<48), R5                // movk x5, #0x8421, lsl #48

@gopherbot
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Change https://go.dev/cl/399455 mentions this issue: cmd/asm: fix MOVK when constant has high bit set

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