[go] cmd/compile: rewriteFixedLoad: ensure AuxInt is sign-extended

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Keith Randall (Gerrit)

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1:26 AM (4 hours ago) 1:26 AM

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Keith Randall submitted the change

Change information

Commit message:

cmd/compile: rewriteFixedLoad: ensure AuxInt is sign-extended

CL 701297 accidentailly broke the type casting behavior for Hash.

Previously, the generated rules for Hash shared a common pattern:

    v.AuxInt = int32ToAuxInt(fixed32(config, sym, off))

which inherently equaled to a signed-extend:

    v.AuxInt = int64(int32(types.TypeHash(...)))

The pattern in CL 701297 was however:

    v.AuxInt = int64(types.TypeHash(t))

Since types.TypeHash() returns a uint32, casting it to a wider integer
implies zero-extend. This diverges from the definition of AuxInt, in
which "Unused portions are filled by sign-extending the used portion,
even if the represented value is unsigned."

As a result, ssa.checkFunc(), where AuxInt is checked against the
mentioned rule, is unhappy and shouts:

    internal compiler error: 'typeAsserts': bad int32 AuxInt value for v1317

Reproduce it with:

    GOARCH=mips go tool compile -m -d=ssa/check/on test/devirtualization.go

This is only reproducible with GOARCH=mips/mipsle (cross and native).
Probably the rewrite rules of other architectures prevent Hash from
running into rewriteFixedLoad.

Fix it by emit sign-extend properly. Additionally, do the same for Kind_
as reflectdata.ABIKindOfType() also returns a fragile unsigned interger
(uint8).

Updates #67304

Change-Id: Ib4f3c94c0e3908698868449db2fdcdf4541f2e7e

Reviewed-on: https://go-review.googlesource.com/c/go/+/744860

Reviewed-by: Cherry Mui <cher...@google.com>

Reviewed-by: Jake Bailey <jacob.b...@gmail.com>

Reviewed-by: Keith Randall <k...@golang.org>

Auto-Submit: Keith Randall <k...@golang.org>

Reviewed-by: Keith Randall <k...@google.com>

LUCI-TryBot-Result: Go LUCI <golang...@luci-project-accounts.iam.gserviceaccount.com>

Files:

M src/cmd/compile/internal/ssa/rewrite.go

Change size: XS

Delta: 1 file changed, 2 insertions(+), 2 deletions(-)

Branch: refs/heads/master

Submit Requirements:

Code-Review: +1 by Jake Bailey, +2 by Keith Randall, +1 by Keith Randall, +1 by Cherry Mui
TryBots-Pass: LUCI-TryBot-Result+1 by Go LUCI

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