[go] cmd/compile: fix misscompile in rewrite generic rules

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Gopher Robot (Gerrit)

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Jun 30, 2026, 1:06:58 PM (yesterday) Jun 30

to Jorropo, goph...@pubsubhelper.golang.org, golang-...@googlegroups.com, Junyang Shao, Keith Randall, Keith Randall, golang...@luci-project-accounts.iam.gserviceaccount.com, Martin Möhrmann, golang-co...@googlegroups.com

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Change information

Commit message:

cmd/compile: fix misscompile in rewrite generic rules

We canonicalize *sh*x(32|16|8) x (Const*) to *sh*x64 x (Const64)
however for the shift type we were using the shift's type.

This is wrong since if we have let's say Rsh32x32 <uint32>
we would generate a Const64 with a type size of 4 (given it
takes the uint32 type).

This causes me confirmed crashes, maybe misscompilations too but
I didn't tried coming up with one.

Change-Id: Idcef7a371836524aa6649e13424431d716497860

Reviewed-on: https://go-review.googlesource.com/c/go/+/795240

Auto-Submit: Jorropo <jorro...@gmail.com>

Auto-Submit: Junyang Shao <shaoj...@google.com>

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

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

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

Reviewed-by: Junyang Shao <shaoj...@google.com>

Files:

M src/cmd/compile/internal/ssa/_gen/generic.rules
M src/cmd/compile/internal/ssa/rewritegeneric.go

Change size: L

Delta: 2 files changed, 144 insertions(+), 180 deletions(-)

Branch: refs/heads/master

Submit Requirements:

Code-Review: +1 by Keith Randall, +1 by Junyang Shao, +2 by Keith Randall
TryBots-Pass: LUCI-TryBot-Result+1 by golang...@luci-project-accounts.iam.gserviceaccount.com

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