[dev.regabi] cmd/compile: fix escape analysis problem with closures

In reflect.methodWrapper, we call escape analysis without including the
full batch of dependent functions, including the closure functions.
Because of this, we haven't created locations for the params/local
variables of a closure when we are processing a function that
inlines that closure. (Whereas in the normal compilation of the
function, we do call with the full batch.) To deal with this, I am
creating locations for the params/local variables of a closure when
needed.

Without this fix, the new test closure6.go would fail.

Updates #43818

Change-Id: I5f91cfb6f35efe2937ef88cbcc468e403e0da9ad
Reviewed-on: https://go-review.googlesource.com/c/go/+/285677
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Dan Scales <danscales@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/escape/escape.go

@@ -781,6 +781,16 @@ func (e *escape) exprSkipInit(k hole, n ir.Node) {
 				}
 			}
 
+			for _, n := range fn.Dcl {
+				// Add locations for local variables of the
+				// closure, if needed, in case we're not including
+				// the closure func in the batch for escape
+				// analysis (happens for escape analysis called
+				// from reflectdata.methodWrapper)
+				if n.Op() == ir.ONAME && n.Opt == nil {
+					e.with(fn).newLoc(n, false)
+				}
+			}
 			e.walkFunc(fn)
 		}
 

test/closure6.go

@@ -0,0 +1,18 @@
+// compile
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type Float64Slice []float64
+
+func (a Float64Slice) Search1(x float64) int {
+	f := func(q int) bool { return a[q] >= x }
+	i := 0
+	if !f(3) {
+		i = 5
+	}
+	return i
+}