compiler: fix equally named structs in different scopes

For example, in this code:

    type kv struct {
           v float32
    }

    func foo(a *kv) {
           type kv struct {
                   v byte
           }
    }

Both 'kv' types would be given the same LLVM type, even though they are
different types! This is fixed by only creating a LLVM type once per Go
type (types.Type).

As an added bonus, this change gives a performance improvement of about
0.4%. Not that much, but certainly not nothing for such a small change.

compiler/compiler.go

@@ -23,7 +23,7 @@ import (
 // Version of the compiler pacakge. Must be incremented each time the compiler
 // package changes in a way that affects the generated LLVM module.
 // This version is independent of the TinyGo version number.
-const Version = 17 // last change: add math.arch* aliases
+const Version = 18 // last change: fix duplicated named structs
 
 func init() {
 	llvm.InitializeAllTargets()
@@ -74,6 +74,7 @@ type compilerContext struct {
 	cu               llvm.Metadata
 	difiles          map[string]llvm.Metadata
 	ditypes          map[types.Type]llvm.Metadata
+	llvmTypes        map[types.Type]llvm.Type
 	machine          llvm.TargetMachine
 	targetData       llvm.TargetData
 	intType          llvm.Type
@@ -94,6 +95,7 @@ func newCompilerContext(moduleName string, machine llvm.TargetMachine, config *C
 		DumpSSA:     dumpSSA,
 		difiles:     make(map[string]llvm.Metadata),
 		ditypes:     make(map[types.Type]llvm.Metadata),
+		llvmTypes:   make(map[types.Type]llvm.Type),
 		machine:     machine,
 		targetData:  machine.CreateTargetData(),
 		astComments: map[string]*ast.CommentGroup{},
@@ -315,10 +317,23 @@ func (c *compilerContext) getLLVMRuntimeType(name string) llvm.Type {
 	return c.getLLVMType(typ)
 }
 
-// getLLVMType creates and returns a LLVM type for a Go type. In the case of
-// named struct types (or Go types implemented as named LLVM structs such as
-// strings) it also creates it first if necessary.
+// getLLVMType returns a LLVM type for a Go type. It doesn't recreate already
+// created types. This is somewhat important for performance, but especially
+// important for named struct types (which should only be created once).
 func (c *compilerContext) getLLVMType(goType types.Type) llvm.Type {
+	// Try to load the LLVM type from the cache.
+	if t, ok := c.llvmTypes[goType]; ok {
+		return t
+	}
+	// Not already created, so adding this type to the cache.
+	llvmType := c.makeLLVMType(goType)
+	c.llvmTypes[goType] = llvmType
+	return llvmType
+}
+
+// makeLLVMType creates a LLVM type for a Go type. Don't call this, use
+// getLLVMType instead.
+func (c *compilerContext) makeLLVMType(goType types.Type) llvm.Type {
 	switch typ := goType.(type) {
 	case *types.Array:
 		elemType := c.getLLVMType(typ.Elem())
@@ -367,12 +382,10 @@ func (c *compilerContext) getLLVMType(goType types.Type) llvm.Type {
 			// LLVM. This is because it is otherwise impossible to create
 			// self-referencing types such as linked lists.
 			llvmName := typ.Obj().Pkg().Path() + "." + typ.Obj().Name()
-			llvmType := c.mod.GetTypeByName(llvmName)
-			if llvmType.IsNil() {
-				llvmType = c.ctx.StructCreateNamed(llvmName)
-				underlying := c.getLLVMType(st)
-				llvmType.StructSetBody(underlying.StructElementTypes(), false)
-			}
+			llvmType := c.ctx.StructCreateNamed(llvmName)
+			c.llvmTypes[goType] = llvmType // avoid infinite recursion
+			underlying := c.getLLVMType(st)
+			llvmType.StructSetBody(underlying.StructElementTypes(), false)
 			return llvmType
 		}
 		return c.getLLVMType(typ.Underlying())

compiler/testdata/basic.go

@@ -55,3 +55,18 @@ func complexMul(x, y complex64) complex64 {
 }
 
 // TODO: complexDiv (requires runtime call)
+
+// A type 'kv' also exists in function foo. Test that these two types don't
+// conflict with each other.
+type kv struct {
+	v float32
+}
+
+func foo(a *kv) {
+	// Define a new 'kv' type.
+	type kv struct {
+		v byte
+	}
+	// Use this type.
+	func(b *kv) {}(nil)
+}

compiler/testdata/basic.ll

@@ -3,6 +3,9 @@ source_filename = "basic.go"
 target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
 target triple = "wasm32--wasi"
 
+%main.kv = type { float }
+%main.kv.0 = type { i8 }
+
 declare noalias nonnull i8* @runtime.alloc(i32, i8*, i8*)
 
 define hidden void @main.init(i8* %context, i8* %parentHandle) unnamed_addr {
@@ -98,3 +101,14 @@ entry:
   %7 = insertvalue { float, float } %6, float %5, 1
   ret { float, float } %7
 }
+
+define hidden void @main.foo(%main.kv* dereferenceable_or_null(4) %a, i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  call void @"main.foo$1"(%main.kv.0* null, i8* undef, i8* undef)
+  ret void
+}
+
+define hidden void @"main.foo$1"(%main.kv.0* dereferenceable_or_null(1) %b, i8* %context, i8* %parentHandle) unnamed_addr {
+entry:
+  ret void
+}