The large-function phi placement algorithm evidently doesn't like the
same pseudo-variable being used to represent expressions of varying
types.
Instead, use the same tactic as used for "valVar" (ssa.go:6585--6587),
which is to just generate a fresh marker node each time.
Maybe we could just use the OMIN/OMAX nodes themselves as the key
(like we do for OANDAND/OOROR), but that just seems needlessly risky
for negligible memory savings. Using fresh marker values each time
seems obviously safe by comparison.
Fixes#61041.
Change-Id: Ie2600c9c37b599c2e26ae01f5f8a433025d7fd08
Reviewed-on: https://go-review.googlesource.com/c/go/+/506679
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Our large-function phi placement algorithm is incompatible with phi
opcodes already existing in the SSA representation. Instead, use simple
variable assignments and have the phi placement algorithm place the phis
we need for min/max.
Turns out the small-function phi placement algorithm doesn't have this
sensitivity, so this bug only occurs in large functions (>500 basic blocks).
Maybe we should document/check that no phis are present when we start
phi placement (regardless of size). Leaving for a potential separate CL.
We should probably also fix the placement algorithm to handle existing
phis correctly. But this CL is probably a lot smaller/safer than
messing with phi placement.
Fixes#60982
Change-Id: I59ba7f506c72b22bc1485099a335d96315ebef67
Reviewed-on: https://go-review.googlesource.com/c/go/+/505756
Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
