1 files changed, 52 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/ssa/fmahash_test.go b/src/cmd/compile/internal/ssa/fmahash_test.go
new file mode 100644
index 0000000..dfa1aa1
--- /dev/null
+++ b/src/cmd/compile/internal/ssa/fmahash_test.go
@@ -0,0 +1,52 @@
+// Copyright 2022 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 ssa_test
+
+import (
+	"internal/testenv"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"testing"
+)
+
+// TestFmaHash checks that the hash-test machinery works properly for a single case.
+// It also runs ssa/check and gccheck to be sure that those are checked at least a
+// little in each run.bash.  It does not check or run the generated code.
+// The test file is however a useful example of fused-vs-cascaded multiply-add.
+func TestFmaHash(t *testing.T) {
+	switch runtime.GOOS {
+	case "linux", "darwin":
+	default:
+		t.Skipf("Slow test, usually avoid it, os=%s not linux or darwin", runtime.GOOS)
+	}
+	switch runtime.GOARCH {
+	case "amd64", "arm64":
+	default:
+		t.Skipf("Slow test, usually avoid it, arch=%s not amd64 or arm64", runtime.GOARCH)
+	}
+
+	testenv.MustHaveGoBuild(t)
+	gocmd := testenv.GoToolPath(t)
+	tmpdir := t.TempDir()
+	source := filepath.Join("testdata", "fma.go")
+	output := filepath.Join(tmpdir, "fma.exe")
+	cmd := testenv.Command(t, gocmd, "build", "-o", output, source)
+	// The hash-dependence on file path name is dodged by specifying "all hashes ending in 1" plus "all hashes ending in 0"
+	// i.e., all hashes.  This will print all the FMAs; this test is only interested in one of them (that should appear near the end).
+	cmd.Env = append(cmd.Env, "GOCOMPILEDEBUG=fmahash=1/0", "GOOS=linux", "GOARCH=arm64", "HOME="+tmpdir)
+	t.Logf("%v", cmd)
+	t.Logf("%v", cmd.Env)
+	b, e := cmd.CombinedOutput()
+	if e != nil {
+		t.Error(e)
+	}
+	s := string(b) // Looking for "GOFMAHASH triggered main.main:24"
+	re := "fmahash(0?) triggered .*fma.go:29:..;.*fma.go:18:.."
+	match := regexp.MustCompile(re)
+	if !match.MatchString(s) {
+		t.Errorf("Expected to match '%s' with \n-----\n%s-----", re, s)
+	}
+}