all: remove support for LLVM 11 and LLVM 12

This removes a lot of backwards compatibility cruft and makes it
possible to start using features that need LLVM 13 or newer.
For example:

  * https://github.com/tinygo-org/tinygo/pull/2637
  * https://github.com/tinygo-org/tinygo/pull/2830

transform/globals.go

@@ -18,17 +18,3 @@ func ApplyFunctionSections(mod llvm.Module) {
 		llvmFn = llvm.NextFunction(llvmFn)
 	}
 }
-
-// DisableTailCalls adds the "disable-tail-calls"="true" function attribute to
-// all functions. This may be necessary, in particular to avoid an error with
-// WebAssembly in LLVM 11.
-func DisableTailCalls(mod llvm.Module) {
-	attribute := mod.Context().CreateStringAttribute("disable-tail-calls", "true")
-	llvmFn := mod.FirstFunction()
-	for !llvmFn.IsNil() {
-		if !llvmFn.IsDeclaration() {
-			llvmFn.AddFunctionAttr(attribute)
-		}
-		llvmFn = llvm.NextFunction(llvmFn)
-	}
-}

transform/transform_test.go

@@ -9,7 +9,6 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
-	"strconv"
 	"strings"
 	"testing"
 
@@ -101,12 +100,6 @@ 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
@@ -116,11 +109,6 @@ 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