libgo patch committed: Promote integer closure return to full word for libffi

Message ID CAOyqgcVTUofxPw7PLLBraMpXA-JM7nSvxj4ywUSDj6yVX2siiA@mail.gmail.com
State New
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  • libgo patch committed: Promote integer closure return to full word for libffi
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Commit Message

Ian Lance Taylor Sept. 17, 2019, 8:24 p.m.
The libffi library expects an integer return type to be promoted to a
full word.  This patch to libgo implements that when returning from a
closure written in Go.  This only matters on big-endian systems when
returning an integer smaller than the pointer size, which is why we
didn't notice it until now.  This fixes GCC PR 91781.  Bootstrapped
and ran Go testsuite on x86_64-pc-linux-gnu.  Bootstrapped and ran
some of the libgo tests on powerpc64-linux-gnu.  Committed to
mainline.

Ian

Patch

Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE	(revision 275809)
+++ gcc/go/gofrontend/MERGE	(working copy)
@@ -1,4 +1,4 @@ 
-ff18e041624b8c23ffcd747f51e9dda945777d2a
+7aabaf8623cf88e2378057476a034093abbe5aab
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: libgo/go/reflect/makefunc_ffi.go
===================================================================
--- libgo/go/reflect/makefunc_ffi.go	(revision 275809)
+++ libgo/go/reflect/makefunc_ffi.go	(working copy)
@@ -28,7 +28,7 @@  func makeCIF(ft *funcType) unsafe.Pointe
 //
 // The ffi_callback handles __go_makefunc_can_recover, and
 // then passes off the data as received from ffi here.
-func ffiCallbackGo(results unsafe.Pointer, params unsafe.Pointer, impl *makeFuncImpl) {
+func ffiCallbackGo(results unsafe.Pointer, params unsafe.Pointer, impl *makeFuncImpl, wordsize int32, bigEndian bool) {
 	ftyp := impl.typ
 	in := make([]Value, 0, len(ftyp.in))
 	ap := params
@@ -42,21 +42,46 @@  func ffiCallbackGo(results unsafe.Pointe
 
 	out := impl.call(in)
 
-	off := uintptr(0)
-	for i, typ := range ftyp.out {
-		v := out[i]
+	checkValue := func(v Value, typ *rtype, addr unsafe.Pointer) {
 		if v.flag&flagRO != 0 {
 			panic("reflect: function created by MakeFunc using " + funcName(impl.fn) +
 				" returned value obtained from unexported field")
 		}
 
-		off = align(off, uintptr(typ.fieldAlign))
-		addr := unsafe.Pointer(uintptr(results) + off)
-
 		// Convert v to type typ if v is assignable to a variable
 		// of type t in the language spec.
 		// See issue 28761.
 		v = v.assignTo("reflect.MakeFunc", typ, addr)
+	}
+
+	// In libffi a single integer return value is always promoted
+	// to a full word. This only matters for integers whose size
+	// is less than the size of a full word. There is similar code
+	// in libgo/runtime/go-reflect-call.c.
+	if len(ftyp.out) == 1 {
+		typ := ftyp.out[0]
+		switch typ.Kind() {
+		case Bool, Int8, Int16, Int32, Uint8, Uint16, Uint32:
+			v := out[0]
+			checkValue(v, typ, nil)
+
+			if bigEndian {
+				results = unsafe.Pointer(uintptr(results) + uintptr(wordsize) - typ.size)
+			}
+
+			memmove(results, v.ptr, typ.size)
+			return
+		}
+	}
+
+	off := uintptr(0)
+	for i, typ := range ftyp.out {
+		v := out[i]
+
+		off = align(off, uintptr(typ.fieldAlign))
+		addr := unsafe.Pointer(uintptr(results) + off)
+
+		checkValue(v, typ, addr)
 
 		if v.flag&flagIndir == 0 && (v.kind() == Ptr || v.kind() == UnsafePointer) {
 			*(*unsafe.Pointer)(addr) = v.ptr
Index: libgo/go/reflect/makefunc_ffi_c.c
===================================================================
--- libgo/go/reflect/makefunc_ffi_c.c	(revision 275809)
+++ libgo/go/reflect/makefunc_ffi_c.c	(working copy)
@@ -25,7 +25,8 @@  void makeFuncFFI(void *cif, void *impl)
    function ffiCall with the pointer to the arguments, the results area,
    and the closure structure.  */
 
-extern void ffiCallbackGo(void *result, void **args, ffi_go_closure *closure)
+extern void ffiCallbackGo(void *result, void **args, ffi_go_closure *closure,
+                          int32 wordsize, _Bool big_endian)
   __asm__ (GOSYM_PREFIX "reflect.ffiCallbackGo");
 
 extern void makefuncfficanrecover(Slice)
@@ -72,7 +73,8 @@  ffi_callback (ffi_cif* cif __attribute__
       makefuncfficanrecover (s);
     }
 
-  ffiCallbackGo(results, args, closure);
+  ffiCallbackGo(results, args, closure, sizeof(ffi_arg),
+                __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__);
 
   if (i < n)
     makefuncreturning ();
Index: libgo/runtime/go-reflect-call.c
===================================================================
--- libgo/runtime/go-reflect-call.c	(revision 275698)
+++ libgo/runtime/go-reflect-call.c	(working copy)
@@ -44,8 +44,8 @@  go_results_size (const struct functype *
 
   types = (const struct _type **) func->out.__values;
 
-  /* A single integer return value is always promoted to a full
-     word.  */
+  /* A single integer return value is always promoted to a full word.
+     There is similar code below and in libgo/go/reflect/makefunc_ffi.go.*/
   if (count == 1)
     {
       switch (types[0]->kind & kindMask)
@@ -57,8 +57,6 @@  go_results_size (const struct functype *
 	case kindUint8:
 	case kindUint16:
 	case kindUint32:
-	case kindInt:
-	case kindUint:
 	  return sizeof (ffi_arg);
 
 	default:
@@ -108,8 +106,8 @@  go_set_results (const struct functype *f
 
   types = (const struct _type **) func->out.__values;
 
-  /* A single integer return value is always promoted to a full
-     word.  */
+  /* A single integer return value is always promoted to a full word.
+     There is similar code above and in libgo/go/reflect/makefunc_ffi.go.*/
   if (count == 1)
     {
       switch (types[0]->kind & kindMask)
@@ -121,8 +119,6 @@  go_set_results (const struct functype *f
 	case kindUint8:
 	case kindUint16:
 	case kindUint32:
-	case kindInt:
-	case kindUint:
 	  {
 	    union
 	    {