reflect: Fix MakeFunc for 386 when returning a struct.

When a 386 function returns a struct, it needs to return using
an rtd instruction that pops the hidden struct parameter off
the stack.  That wasn't happening.

From-SVN: r205551

libgo/go/reflect/makefunc_386.S

@@ -26,8 +26,11 @@ reflect.makeFuncStub:
 	     esp uint32		// 0x0
 	     eax uint32		// 0x4
 	     st0 uint64		// 0x8
+	     rs  int32		// 0x10
 	   }
-	*/
+	   The rs field is set by the function to a non-zero value if
+	   the function takes a struct hidden pointer that must be
+	   popped off the stack.  */
 
 	pushl	%ebp
 .LCFI0:
@@ -73,12 +76,19 @@ reflect.makeFuncStub:
 	movsd	-16(%ebp), %xmm0
 #endif
 
+	movl	-8(%ebp), %edx
+
 	addl	$36, %esp
 	popl	%ebx
 .LCFI3:
 	popl	%ebp
 .LCFI4:
+
+	testl	%edx,%edx
+	jne	1f
 	ret
+1:
+	ret	$4
 .LFE1:
 #ifdef __ELF__
 	.size	reflect.makeFuncStub, . - reflect.makeFuncStub

libgo/go/reflect/makefuncgo_386.go

@@ -16,6 +16,7 @@ type i386Regs struct {
 	esp uint32
 	eax uint32 // Value to return in %eax.
 	st0 uint64 // Value to return in %st(0).
+	sr  int32  // Set to non-zero if hidden struct pointer.
 }
 
 // MakeFuncStubGo implements the 386 calling convention for MakeFunc.
@@ -56,10 +57,12 @@ func MakeFuncStubGo(regs *i386Regs, c *makeFuncImpl) {
 	in := make([]Value, 0, len(ftyp.in))
 	ap := uintptr(regs.esp)
 
+	regs.sr = 0
 	var retPtr unsafe.Pointer
 	if retStruct {
 		retPtr = *(*unsafe.Pointer)(unsafe.Pointer(ap))
 		ap += ptrSize
+		regs.sr = 1
 	}
 
 	for _, rt := range ftyp.in {