cmd/compile: change testing.B.Loop keep alive semantic

This CL implements this initial design of testing.B.Loop's keep variable
alive semantic:
https://github.com/golang/go/issues/61515#issuecomment-2407963248.

Fixes #73137.

Change-Id: I8060470dbcb0dda0819334f3615cc391ff0f6501
Reviewed-on: https://go-review.googlesource.com/c/go/+/716660
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>

2 files changed, 51 insertions, 37 deletions

diff --git a/test/bloop.go b/test/bloop.go
new file mode 100644
index 0000000000..0d2dcba0ac
--- /dev/null
+++ b/test/bloop.go
@@ -0,0 +1,51 @@
+// errorcheck -0 -m
+
+// Copyright 2025 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.
+
+// Test keeping statements results in testing.B.Loop alive.
+// See issue #61515, #73137.
+
+package foo
+
+import "testing"
+
+func caninline(x int) int { // ERROR "can inline caninline"
+	return x
+}
+
+var something int
+
+func caninlineNoRet(x int) { // ERROR "can inline caninlineNoRet"
+	something = x
+}
+
+func caninlineVariadic(x ...int) { // ERROR "can inline caninlineVariadic" "x does not escape"
+	something = x[0]
+}
+
+func test(b *testing.B, localsink, cond int) { // ERROR "leaking param: b"
+	for i := 0; i < b.N; i++ {
+		caninline(1) // ERROR "inlining call to caninline"
+	}
+	for b.Loop() { // ERROR "inlining call to testing\.\(\*B\)\.Loop"
+		caninline(1)                 // ERROR "inlining call to caninline" "function result will be kept alive" ".* does not escape"
+		caninlineNoRet(1)            // ERROR "inlining call to caninlineNoRet" "function arg will be kept alive" ".* does not escape"
+		caninlineVariadic(1)         // ERROR "inlining call to caninlineVariadic" "function arg will be kept alive" ".* does not escape"
+		caninlineVariadic(localsink) // ERROR "inlining call to caninlineVariadic" "localsink will be kept alive" ".* does not escape"
+		localsink = caninline(1)     // ERROR "inlining call to caninline" "localsink will be kept alive" ".* does not escape"
+		localsink += 5               // ERROR "localsink will be kept alive" ".* does not escape"
+		localsink, cond = 1, 2       // ERROR "localsink will be kept alive" "cond will be kept alive" ".* does not escape"
+		if cond > 0 {
+			caninline(1) // ERROR "inlining call to caninline" "function result will be kept alive" ".* does not escape"
+		}
+		switch cond {
+		case 2:
+			caninline(1) // ERROR "inlining call to caninline" "function result will be kept alive" ".* does not escape"
+		}
+		{
+			caninline(1) // ERROR "inlining call to caninline" "function result will be kept alive" ".* does not escape"
+		}
+	}
+}
diff --git a/test/inline_testingbloop.go b/test/inline_testingbloop.go
deleted file mode 100644
index 702a652f56..0000000000
--- a/test/inline_testingbloop.go
+++ /dev/null
@@ -1,37 +0,0 @@
-// errorcheck -0 -m
-
-// Copyright 2024 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.
-
-// Test no inlining of function calls in testing.B.Loop.
-// See issue #61515.
-
-package foo
-
-import "testing"
-
-func caninline(x int) int { // ERROR "can inline caninline"
-	return x
-}
-
-func test(b *testing.B) { // ERROR "leaking param: b"
-	for i := 0; i < b.N; i++ {
-		caninline(1) // ERROR "inlining call to caninline"
-	}
-	for b.Loop() { // ERROR "skip inlining within testing.B.loop" "inlining call to testing\.\(\*B\)\.Loop"
-		caninline(1)
-	}
-	for i := 0; i < b.N; i++ {
-		caninline(1) // ERROR "inlining call to caninline"
-	}
-	for b.Loop() { // ERROR "skip inlining within testing.B.loop" "inlining call to testing\.\(\*B\)\.Loop"
-		caninline(1)
-	}
-	for i := 0; i < b.N; i++ {
-		caninline(1) // ERROR "inlining call to caninline"
-	}
-	for b.Loop() { // ERROR "skip inlining within testing.B.loop" "inlining call to testing\.\(\*B\)\.Loop"
-		caninline(1)
-	}
-}