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cmd/compile: fix checkptr handling of &^

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checkptr has code to recognize &^ expressions, but it didn't take into
account that "p &^ x" gets rewritten to "p & ^x" during walk, which
resulted in false positive diagnostics.

This CL changes walkexpr to mark OANDNOT expressions with Implicit
when they're rewritten to OAND, so that walkCheckPtrArithmetic can
still recognize them later.

It would be slightly more idiomatic to instead mark the OBITNOT
expression as Implicit (as it's a compiler-generated Node), but the
OBITNOT expression might get constant folded. It's not worth the extra
complexity/subtlety of relying on n.Right.Orig, so we set Implicit on
the OAND node instead.

To atone for this transgression, I add documentation for nodeImplicit.

Fixes #40917.

Change-Id: I386304171ad299c530e151e5924f179e9a5fd5b8
Reviewed-on: https://go-review.googlesource.com/c/go/+/249477
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
This commit is contained in:
Matthew Dempsky 2020-08-19 21:39:12 -07:00
parent 268dd2e5a7
commit e94544cf01
5 changed files with 40 additions and 3 deletions
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4
src/cmd/compile/internal/gc/syntax.go
View file

@ -141,8 +141,8 @@ const (
nodeInitorder, _ // tracks state during init1; two bits
_, _ // second nodeInitorder bit
_, nodeHasBreak
_, nodeNoInline // used internally by inliner to indicate that a function call should not be inlined; set for OCALLFUNC and OCALLMETH only
_, nodeImplicit
_, nodeNoInline // used internally by inliner to indicate that a function call should not be inlined; set for OCALLFUNC and OCALLMETH only
_, nodeImplicit // implicit OADDR or ODEREF; ++/-- statement represented as OASOP; or ANDNOT lowered to OAND
_, nodeIsDDD // is the argument variadic
_, nodeDiag // already printed error about this
_, nodeColas // OAS resulting from :=