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cmd/compile: fix unified IR's pointer-shaping

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In CL 424734, I implemented pointer shaping for unified IR. Evidently
though, we didn't have any test cases that check that uses of
pointer-shaped expressions were handled correctly.

In the reported test case, the struct field "children items[*node[T]]"
gets shaped to "children items[go.shape.*uint8]" (underlying type
"[]go.shape.*uint8"); and so the expression "n.children[i]" has type
"go.shape.*uint8" and the ".items" field selection expression fails.

The fix implemented in this CL is that any expression of derived type
now gets an explicit "reshape" operation applied to it, to ensure it
has the appropriate type for its context. E.g., the "n.children[i]"
OINDEX expression above gets "reshaped" from "go.shape.*uint8" to
"*node[go.shape.int]", allowing the field selection to succeed.

This CL also adds a "-d=reshape" compiler debugging flag, because I
anticipate debugging reshaping operations will be something to come up
again in the future.

Fixes #54535.

Change-Id: Id847bd8f51300d2491d679505ee4d2e974ca972a
Reviewed-on: https://go-review.googlesource.com/c/go/+/424936
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: hopehook <hopehook@qq.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Matthew Dempsky 2022-08-18 20:59:26 -07:00
parent 0a6e1fa986
commit 6985ab27df
5 changed files with 90 additions and 1 deletions
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1
src/cmd/compile/internal/base/debug.go
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@ -34,6 +34,7 @@ type DebugFlags struct {
NoRefName int `help:"do not include referenced symbol names in object file"`
PCTab string `help:"print named pc-value table\nOne of: pctospadj, pctofile, pctoline, pctoinline, pctopcdata"`
Panic int `help:"show all compiler panics"`
Reshape int `help:"print information about expression reshaping"`
Slice int `help:"print information about slice compilation"`
SoftFloat int `help:"force compiler to emit soft-float code"`
SyncFrames int `help:"how many writer stack frames to include at sync points in unified export data"`