all: add LLVM 12 support

Originally based on a PR by @QuLogic, but extended a lot to get all
tests to pass.

compiler/compiler_test.go

@@ -41,6 +41,13 @@ func TestCompiler(t *testing.T) {
 		t.Skip("compiler tests require LLVM 11 or above, got LLVM ", llvm.Version)
 	}
 
+	// Determine Go minor version (e.g. 16 in go1.16.3).
+	_, goMinor, err := goenv.GetGorootVersion(goenv.Get("GOROOT"))
+	if err != nil {
+		t.Fatal("could not read Go version:", err)
+	}
+
+	// Determine which tests to run, depending on the Go and LLVM versions.
 	tests := []testCase{
 		{"basic.go", "", ""},
 		{"pointer.go", "", ""},
@@ -58,12 +65,11 @@ func TestCompiler(t *testing.T) {
 		{"intrinsics.go", "wasm", ""},
 		{"gc.go", "", ""},
 	}
-
-	_, minor, err := goenv.GetGorootVersion(goenv.Get("GOROOT"))
-	if err != nil {
-		t.Fatal("could not read Go version:", err)
+	if llvmMajor >= 12 {
+		tests = append(tests, testCase{"intrinsics.go", "cortex-m-qemu", ""})
+		tests = append(tests, testCase{"intrinsics.go", "wasm", ""})
 	}
-	if minor >= 17 {
+	if goMinor >= 17 {
 		tests = append(tests, testCase{"go1.17.go", "", ""})
 	}
 
@@ -201,6 +207,12 @@ func fuzzyEqualIR(s1, s2 string) bool {
 // stripped out.
 func filterIrrelevantIRLines(lines []string) []string {
 	var out []string
+	llvmVersion, err := strconv.Atoi(strings.Split(llvm.Version, ".")[0])
+	if err != nil {
+		// Note: this should never happen and if it does, it will always happen
+		// for a particular build because llvm.Version is a constant.
+		panic(err)
+	}
 	for _, line := range lines {
 		line = strings.Split(line, ";")[0]    // strip out comments/info
 		line = strings.TrimRight(line, "\r ") // drop '\r' on Windows and remove trailing spaces from comments
@@ -210,6 +222,11 @@ func filterIrrelevantIRLines(lines []string) []string {
 		if strings.HasPrefix(line, "source_filename = ") {
 			continue
 		}
+		if llvmVersion < 12 && strings.HasPrefix(line, "attributes ") {
+			// Ignore attribute groups. These may change between LLVM versions.
+			// Right now test outputs are for LLVM 12.
+			continue
+		}
 		out = append(out, line)
 	}
 	return out