compiler: make all functions unnamed_addr

In Go, function pointers are not comparable. This means that the address
itself is not significant and functions can therefore be merged.

Add the unnamed_addr attribute to all functions to learn LLVM about this
fact. At the moment the mergefunc pass hasn't been enabled, but it
should be in the future to reduce code size.

compiler/compiler.go

@@ -342,6 +342,7 @@ func (c *Compiler) Compile(mainPath string) error {
 		// the real function with them.
 		llvmFn := c.mod.NamedFunction(fn.LinkName() + "$defer")
 		llvmFn.SetLinkage(llvm.InternalLinkage)
+		llvmFn.SetUnnamedAddr(true)
 		entry := c.ctx.AddBasicBlock(llvmFn, "entry")
 		c.builder.SetInsertPointAtEnd(entry)
 		deferRawPtr := llvmFn.Param(0)
@@ -382,6 +383,7 @@ func (c *Compiler) Compile(mainPath string) error {
 		// parameters and to call the function pointer with them.
 		llvmFn := thunk.fn
 		llvmFn.SetLinkage(llvm.InternalLinkage)
+		llvmFn.SetUnnamedAddr(true)
 		entry := c.ctx.AddBasicBlock(llvmFn, "entry")
 		// TODO: set the debug location - perhaps the location of the rundefers
 		// call?
@@ -434,6 +436,7 @@ func (c *Compiler) Compile(mainPath string) error {
 	// that calls the initializer of each package.
 	initFn := c.ir.GetFunction(c.ir.Program.ImportedPackage("runtime").Members["initAll"].(*ssa.Function))
 	initFn.LLVMFn.SetLinkage(llvm.InternalLinkage)
+	initFn.LLVMFn.SetUnnamedAddr(true)
 	if c.Debug {
 		difunc, err := c.attachDebugInfo(initFn)
 		if err != nil {
@@ -451,6 +454,7 @@ func (c *Compiler) Compile(mainPath string) error {
 
 	mainWrapper := c.ir.GetFunction(c.ir.Program.ImportedPackage("runtime").Members["mainWrapper"].(*ssa.Function))
 	mainWrapper.LLVMFn.SetLinkage(llvm.InternalLinkage)
+	mainWrapper.LLVMFn.SetUnnamedAddr(true)
 	if c.Debug {
 		difunc, err := c.attachDebugInfo(mainWrapper)
 		if err != nil {
@@ -873,6 +877,7 @@ func (c *Compiler) wrapInterfaceInvoke(f *ir.Function) (llvm.Value, error) {
 	wrapFnType := llvm.FunctionType(fnType.ReturnType(), paramTypes, false)
 	wrapper := llvm.AddFunction(c.mod, f.LinkName()+"$invoke", wrapFnType)
 	wrapper.SetLinkage(llvm.InternalLinkage)
+	wrapper.SetUnnamedAddr(true)
 
 	// add debug info
 	if c.Debug {
@@ -1343,6 +1348,7 @@ func (c *Compiler) parseFunc(frame *Frame) error {
 	}
 	if !frame.fn.IsExported() {
 		frame.fn.LLVMFn.SetLinkage(llvm.InternalLinkage)
+		frame.fn.LLVMFn.SetUnnamedAddr(true)
 	}
 	if frame.fn.IsInterrupt() && strings.HasPrefix(c.Triple, "avr") {
 		frame.fn.LLVMFn.SetFunctionCallConv(85) // CallingConv::AVR_SIGNAL
@@ -3636,6 +3642,7 @@ func (c *Compiler) ExternalInt64AsPtr() {
 			// better performance, but export a new wrapper function with the
 			// correct calling convention.
 			fn.SetLinkage(llvm.InternalLinkage)
+			fn.SetUnnamedAddr(true)
 			entryBlock := llvm.AddBasicBlock(externalFn, "entry")
 			c.builder.SetInsertPointAtEnd(entryBlock)
 			callParams := []llvm.Value{}