reflect, runtime, runtime/cgo: use ppc64 asm constant for fixed frame size

Shared libraries on ppc64le will require a larger minimum stack frame (because
the ABI mandates that the TOC pointer is available at 24(R1)). Part 3 of that
is using a #define in the ppc64 assembly to refer to the size of the fixed
part of the stack (finding all these took me about a week!).

Change-Id: I50f22fe1c47af1ec59da1bd7ea8f84a4750df9b7
Reviewed-on: https://go-review.googlesource.com/15525
Reviewed-by: Ian Lance Taylor <iant@golang.org>

1 files changed, 31 insertions, 0 deletions

diff --git a/src/runtime/asm_ppc64x.h b/src/runtime/asm_ppc64x.h
new file mode 100644
index 0000000000..a2d2e5beaf
--- /dev/null
+++ b/src/runtime/asm_ppc64x.h
@@ -0,0 +1,31 @@
+// Copyright 2015 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// FIXED_FRAME defines the size of the fixed part of a stack frame. A stack
+// frame looks like this:
+//
+// +---------------------+
+// | local variable area |
+// +---------------------+
+// | argument area       |
+// +---------------------+ <- R1+FIXED_FRAME
+// | fixed area          |
+// +---------------------+ <- R1
+//
+// So a function that sets up a stack frame at all uses as least FIXED_FRAME
+// bytes of stack.  This mostly affects assembly that calls other functions
+// with arguments (the arguments should be stored at FIXED_FRAME+0(R1),
+// FIXED_FRAME+8(R1) etc) and some other low-level places.
+//
+// The reason for using a constant is when code is compiled as PIC on ppc64le
+// the fixed part of the stack is 32 bytes large (although PIC is not actually
+// supported yet).
+
+#ifdef GOARCH_ppc64
+#define FIXED_FRAME 8
+#endif
+
+#ifdef GOARCH_ppc64le
+#define FIXED_FRAME 8
+#endif