cgo: add //go: pragmas to generated functions and globals

This patch adds //go: pragmas directly to declared functions and
globals found during CGo processing. This simplifies the logic in the
compiler: it no longer has to consider special "C." prefixed function
names. It also makes the cgo pass more flexible in the pragmas it emits
for functions and global variables.

compiler/compiler.go

@@ -2802,9 +2802,8 @@ func (b *builder) createUnOp(unop *ssa.UnOp) (llvm.Value, error) {
 			//     var C.add unsafe.Pointer
 			// Instead of a load from the global, create a bitcast of the
 			// function pointer itself.
-			globalName := b.getGlobalInfo(unop.X.(*ssa.Global)).linkName
-			name := globalName[:len(globalName)-len("$funcaddr")]
-			fn := b.getFunction(b.fn.Pkg.Members["C."+name].(*ssa.Function))
+			name := strings.TrimSuffix(unop.X.(*ssa.Global).Name(), "$funcaddr")
+			fn := b.getFunction(b.fn.Pkg.Members[name].(*ssa.Function))
 			if fn.IsNil() {
 				return llvm.Value{}, b.makeError(unop.Pos(), "cgo function not found: "+name)
 			}

compiler/symbol.go

@@ -208,14 +208,9 @@ func (c *compilerContext) getFunction(fn *ssa.Function) llvm.Value {
 // present in *ssa.Function, such as the link name and whether it should be
 // exported.
 func (c *compilerContext) getFunctionInfo(f *ssa.Function) functionInfo {
-	info := functionInfo{}
-	if strings.HasPrefix(f.Name(), "C.") {
-		// Created by CGo: such a name cannot be created by regular C code.
-		info.linkName = f.Name()[2:]
-		info.exported = true
-	} else {
+	info := functionInfo{
 		// Pick the default linkName.
-		info.linkName = f.RelString(nil)
+		linkName: f.RelString(nil),
 	}
 	// Check for //go: pragmas, which may change the link name (among others).
 	info.parsePragmas(f)
@@ -460,20 +455,14 @@ func (c *compilerContext) getGlobal(g *ssa.Global) llvm.Value {
 
 // getGlobalInfo returns some information about a specific global.
 func (c *compilerContext) getGlobalInfo(g *ssa.Global) globalInfo {
-	info := globalInfo{}
-	if strings.HasPrefix(g.Name(), "C.") {
-		// Created by CGo: such a name cannot be created by regular C code.
-		info.linkName = g.Name()[2:]
-		info.extern = true
-	} else {
+	info := globalInfo{
 		// Pick the default linkName.
-		info.linkName = g.RelString(nil)
-		// Check for //go: pragmas, which may change the link name (among
-		// others).
-		doc := c.astComments[info.linkName]
-		if doc != nil {
-			info.parsePragmas(doc)
-		}
+		linkName: g.RelString(nil),
+	}
+	// Check for //go: pragmas, which may change the link name (among others).
+	doc := c.astComments[info.linkName]
+	if doc != nil {
+		info.parsePragmas(doc)
 	}
 	return info
 }