all: change special type __volatile to pragma //go:volatile

This is one step towards removing unnecessary special casts in most
cases. It is also part of removing as much magic as possible from the
compiler (the pragma is explicit, the special name is not).

compiler/compiler.go

@@ -1528,9 +1528,8 @@ func (c *Compiler) parseInstr(frame *Frame, instr ssa.Instruction) error {
 		}
 		store := c.builder.CreateStore(llvmVal, llvmAddr)
 		valType := instr.Addr.Type().(*types.Pointer).Elem()
-		if valType, ok := valType.(*types.Named); ok && valType.Obj().Name() == "__volatile" {
-			// Magic type name to make this store volatile, for memory-mapped
-			// registers.
+		if c.ir.IsVolatile(valType) {
+			// Volatile store, for memory-mapped registers.
 			store.SetVolatile(true)
 		}
 		return nil
@@ -3040,9 +3039,8 @@ func (c *Compiler) parseUnOp(frame *Frame, unop *ssa.UnOp) (llvm.Value, error) {
 	case token.MUL: // *x, dereference pointer
 		valType := unop.X.Type().(*types.Pointer).Elem()
 		load := c.builder.CreateLoad(x, "")
-		if valType, ok := valType.(*types.Named); ok && valType.Obj().Name() == "__volatile" {
-			// Magic type name to make this load volatile, for memory-mapped
-			// registers.
+		if c.ir.IsVolatile(valType) {
+			// Volatile load, for memory-mapped registers.
 			load.SetVolatile(true)
 		}
 		return load, nil