all: refactor reflect package

This is a big commit that changes the way runtime type information is stored in
the binary. Instead of compressing it and storing it in a number of sidetables,
it is stored similar to how the Go compiler toolchain stores it (but still more
compactly).

This has a number of advantages:

  * It is much easier to add new features to reflect support. They can simply
    be added to these structs without requiring massive changes (especially in
    the reflect lowering pass).
  * It removes the reflect lowering pass, which was a large amount of hard to
    understand and debug code.
  * The reflect lowering pass also required merging all LLVM IR into one
    module, which is terrible for performance especially when compiling large
    amounts of code. See issue 2870 for details.
  * It is (probably!) easier to reason about for the compiler.

The downside is that it increases code size a bit, especially when reflect is
involved. I hope to fix some of that in later patches.

builder/sizes.go

@@ -118,10 +118,6 @@ var (
 	//   pack:   data created when storing a constant in an interface for example
 	//   string: buffer behind strings
 	packageSymbolRegexp = regexp.MustCompile(`\$(alloc|embedfsfiles|embedfsslice|embedslice|pack|string)(\.[0-9]+)?$`)
-
-	// Reflect sidetables. Created by the reflect lowering pass.
-	// See src/reflect/sidetables.go.
-	reflectDataRegexp = regexp.MustCompile(`^reflect\.[a-zA-Z]+Sidetable$`)
 )
 
 // readProgramSizeFromDWARF reads the source location for each line of code and
@@ -375,7 +371,7 @@ func loadProgramSize(path string, packagePathMap map[string]string) (*programSiz
 			if section.Flags&elf.SHF_ALLOC == 0 {
 				continue
 			}
-			if packageSymbolRegexp.MatchString(symbol.Name) || reflectDataRegexp.MatchString(symbol.Name) {
+			if packageSymbolRegexp.MatchString(symbol.Name) {
 				addresses = append(addresses, addressLine{
 					Address:    symbol.Value,
 					Length:     symbol.Size,
@@ -836,9 +832,8 @@ func findPackagePath(path string, packagePathMap map[string]string) string {
 		} else if packageSymbolRegexp.MatchString(path) {
 			// Parse symbol names like main$alloc or runtime$string.
 			packagePath = path[:strings.LastIndex(path, "$")]
-		} else if reflectDataRegexp.MatchString(path) {
-			// Parse symbol names like reflect.structTypesSidetable.
-			packagePath = "Go reflect data"
+		} else if path == "<Go type>" {
+			packagePath = "Go types"
 		} else if path == "<Go interface assert>" {
 			// Interface type assert, generated by the interface lowering pass.
 			packagePath = "Go interface assert"