1 files changed, 117 insertions, 0 deletions
diff --git a/test/mergemul.go b/test/mergemul.go
new file mode 100644
index 0000000..a23115b
--- /dev/null
+++ b/test/mergemul.go
@@ -0,0 +1,117 @@
+// runoutput
+
+// Copyright 2017 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"
+
+// Check that expressions like (c*n + d*(n+k)) get correctly merged by
+// the compiler into (c+d)*n + d*k (with c+d and d*k computed at
+// compile time).
+//
+// The merging is performed by a combination of the multiplication
+// merge rules
+//  (c*n + d*n) -> (c+d)*n
+// and the distributive multiplication rules
+//  c * (d+x)  ->  c*d + c*x
+
+// Generate a MergeTest that looks like this:
+//
+//   a8, b8 = m1*n8 + m2*(n8+k), (m1+m2)*n8 + m2*k
+//   if a8 != b8 {
+// 	   // print error msg and panic
+//   }
+func makeMergeAddTest(m1, m2, k int, size string) string {
+
+	model := "    a" + size + ", b" + size
+	model += fmt.Sprintf(" = %%d*n%s + %%d*(n%s+%%d), (%%d+%%d)*n%s + (%%d*%%d)", size, size, size)
+
+	test := fmt.Sprintf(model, m1, m2, k, m1, m2, m2, k)
+	test += fmt.Sprintf(`
+    if a%s != b%s {
+        fmt.Printf("MergeAddTest(%d, %d, %d, %s) failed\n")
+        fmt.Printf("%%d != %%d\n", a%s, b%s)
+        panic("FAIL")
+    }
+`, size, size, m1, m2, k, size, size, size)
+	return test + "\n"
+}
+
+// Check that expressions like (c*n - d*(n+k)) get correctly merged by
+// the compiler into (c-d)*n - d*k (with c-d and d*k computed at
+// compile time).
+//
+// The merging is performed by a combination of the multiplication
+// merge rules
+//  (c*n - d*n) -> (c-d)*n
+// and the distributive multiplication rules
+//  c * (d-x)  ->  c*d - c*x
+
+// Generate a MergeTest that looks like this:
+//
+//   a8, b8 = m1*n8 - m2*(n8+k), (m1-m2)*n8 - m2*k
+//   if a8 != b8 {
+// 	   // print error msg and panic
+//   }
+func makeMergeSubTest(m1, m2, k int, size string) string {
+
+	model := "    a" + size + ", b" + size
+	model += fmt.Sprintf(" = %%d*n%s - %%d*(n%s+%%d), (%%d-%%d)*n%s - (%%d*%%d)", size, size, size)
+
+	test := fmt.Sprintf(model, m1, m2, k, m1, m2, m2, k)
+	test += fmt.Sprintf(`
+    if a%s != b%s {
+        fmt.Printf("MergeSubTest(%d, %d, %d, %s) failed\n")
+        fmt.Printf("%%d != %%d\n", a%s, b%s)
+        panic("FAIL")
+    }
+`, size, size, m1, m2, k, size, size, size)
+	return test + "\n"
+}
+
+func makeAllSizes(m1, m2, k int) string {
+	var tests string
+	tests += makeMergeAddTest(m1, m2, k, "8")
+	tests += makeMergeAddTest(m1, m2, k, "16")
+	tests += makeMergeAddTest(m1, m2, k, "32")
+	tests += makeMergeAddTest(m1, m2, k, "64")
+	tests += makeMergeSubTest(m1, m2, k, "8")
+	tests += makeMergeSubTest(m1, m2, k, "16")
+	tests += makeMergeSubTest(m1, m2, k, "32")
+	tests += makeMergeSubTest(m1, m2, k, "64")
+	tests += "\n"
+	return tests
+}
+
+func main() {
+	fmt.Println(`package main
+
+import "fmt"
+
+var n8 int8 = 42
+var n16 int16 = 42
+var n32 int32 = 42
+var n64 int64 = 42
+
+func main() {
+    var a8, b8 int8
+    var a16, b16 int16
+    var a32, b32 int32
+    var a64, b64 int64
+`)
+
+	fmt.Println(makeAllSizes(03, 05, 0)) // 3*n + 5*n
+	fmt.Println(makeAllSizes(17, 33, 0))
+	fmt.Println(makeAllSizes(80, 45, 0))
+	fmt.Println(makeAllSizes(32, 64, 0))
+
+	fmt.Println(makeAllSizes(7, 11, +1)) // 7*n + 11*(n+1)
+	fmt.Println(makeAllSizes(9, 13, +2))
+	fmt.Println(makeAllSizes(11, 16, -1))
+	fmt.Println(makeAllSizes(17, 9, -2))
+
+	fmt.Println("}")
+}