cmd/compile: fix pointer maps for morestack

Verified with test and with single step watching changes to register
values across morestack calls, after reload.

Also added stack-growth test with pointer parameters of varying lifetime.

For #40724.

Change-Id: Idb5fe27786ac5c6665a734d41e68d3d39de2f4da
Reviewed-on: https://go-review.googlesource.com/c/go/+/294429
Trust: David Chase <drchase@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>

2 files changed, 80 insertions, 0 deletions

diff --git a/test/abi/uglyfib.go b/test/abi/uglyfib.go
new file mode 100644
index 0000000000..bde3548bee
--- /dev/null
+++ b/test/abi/uglyfib.go
@@ -0,0 +1,79 @@
+// run
+
+//go:build !wasm
+// +build !wasm
+
+// Copyright 2021 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 main
+
+import "fmt"
+
+// This test is designed to provoke a stack growth
+// in a way that very likely leaves junk in the
+// parameter save area if they aren't saved or spilled
+// there, as appropriate.
+
+//go:registerparams
+//go:noinline
+func f(x int, xm1, xm2, p *int) {
+	var y = [2]int{x - 4, 0}
+	if x < 2 {
+		*p += x
+		return
+	}
+	x -= 3
+	g(*xm1, xm2, &x, p)   // xm1 is no longer live.
+	h(*xm2, &x, &y[0], p) // xm2 is no longer live, but was spilled.
+}
+
+//go:registerparams
+//go:noinline
+func g(x int, xm1, xm2, p *int) {
+	var y = [3]int{x - 4, 0, 0}
+	if x < 2 {
+		*p += x
+		return
+	}
+	x -= 3
+	k(*xm2, &x, &y[0], p)
+	h(*xm1, xm2, &x, p)
+}
+
+//go:registerparams
+//go:noinline
+func h(x int, xm1, xm2, p *int) {
+	var y = [4]int{x - 4, 0, 0, 0}
+	if x < 2 {
+		*p += x
+		return
+	}
+	x -= 3
+	k(*xm1, xm2, &x, p)
+	f(*xm2, &x, &y[0], p)
+}
+
+//go:registerparams
+//go:noinline
+func k(x int, xm1, xm2, p *int) {
+	var y = [5]int{x - 4, 0, 0, 0, 0}
+	if x < 2 {
+		*p += x
+		return
+	}
+	x -= 3
+	f(*xm2, &x, &y[0], p)
+	g(*xm1, xm2, &x, p)
+}
+
+func main() {
+	x := 40
+	var y int
+	xm1 := x - 1
+	xm2 := x - 2
+	f(x, &xm1, &xm2, &y)
+
+	fmt.Printf("Fib(%d)=%d\n", x, y)
+}
diff --git a/test/abi/uglyfib.out b/test/abi/uglyfib.out
new file mode 100644
index 0000000000..d892270e20
--- /dev/null
+++ b/test/abi/uglyfib.out
@@ -0,0 +1 @@
+Fib(40)=102334155