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Matthew Dempsky f92741b1d8 cmd/compile/internal/noder: elide statically known "if" statements
In go.dev/cl/517775, I moved the frontend's deadcode elimination pass
into unified IR. But I also made a small enhancement: a branch like
"if x || true" is now detected as always taken, so the else branch can
be eliminated.

However, the inliner also has an optimization for delaying the
introduction of the result temporary variables when there's a single
return statement (added in go.dev/cl/266199). Consequently, the
inliner turns "if x || true { return true }; return true" into:

	if x || true {
		~R0 := true
		goto .i0
	}
	.i0:
	// code that uses ~R0

In turn, this confuses phi insertion, because it doesn't recognize
that the "if" statement is always taken, and so ~R0 will always be
initialized.

With this CL, after inlining we instead produce:

	_ = x || true
	~R0 := true
	goto .i0
	.i0:

Fixes #62211.

Change-Id: Ic8a12c9eb85833ee4e5d114f60e6c47817fce538
Reviewed-on: https://go-review.googlesource.com/c/go/+/522096
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
2023-08-23 18:01:55 +00:00
.github .github: fix templates with multiple labels 2023-07-31 18:28:27 +00:00
api encoding: add AppendEncode and AppendDecode 2023-08-17 16:23:42 +00:00
doc spec: clarify that []byte("") must be non-nil 2023-08-21 23:20:08 +00:00
lib/time lib/time: update to 2023c/2023c 2023-05-03 20:14:11 +00:00
misc os: add tests for UserCacheDir and UserConfigDir 2023-08-21 17:46:57 +00:00
src cmd/compile/internal/noder: elide statically known "if" statements 2023-08-23 18:01:55 +00:00
test cmd/compile/internal/noder: elide statically known "if" statements 2023-08-23 18:01:55 +00:00
.gitattributes all: treat all files as binary, but check in .bat with CRLF 2020-06-08 15:31:43 +00:00
.gitignore internal/platform,cmd/dist: export the list of supported platforms 2023-06-22 19:44:52 +00:00
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CONTRIBUTING.md doc: normalize proposal-process links 2023-03-29 22:00:27 +00:00
go.env cmd/go: additional doc-inspired tests and bug fixes 2023-06-06 19:18:46 +00:00
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