* libgo: Fix PR go/67508, rewrite lfstack packing/unpacking to look more

    like that in Go (Michael Hudson). LP: #1472650.


git-svn-id: svn://anonscm.debian.org/gcccvs/branches/sid/gcc-5@8219 6ca36cf4-e1d1-0310-8c6f-e303bb2178ca

3 files changed, 110 insertions, 0 deletions

diff --git a/debian/changelog b/debian/changelog
index a47fc85..64e7ae9 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -5,6 +5,8 @@ gcc-5 (5.2.1-17) UNRELEASED; urgency=medium
     Closes: #796906.
   * Don't ignore anymore bootstrap comparison failures on sh4. Closes: #796939.
   * Fix stage1 cross build for KFreeBSD. Closes: #796901.
+  * libgo: Fix PR go/67508, rewrite lfstack packing/unpacking to look more
+    like that in Go (Michael Hudson). LP: #1472650.
 
   [ Aurelien Jarno ]
   * Use --with-mips-plt on mips*.
diff --git a/debian/patches/pr67508.diff b/debian/patches/pr67508.diff
new file mode 100644
index 0000000..906a4cf
--- /dev/null
+++ b/debian/patches/pr67508.diff
@@ -0,0 +1,107 @@
+# DP: libgo: Fix PR go/67508, rewrite lfstack packing/unpacking
+# DP: to look more like that in Go
+
+From 95eb3733500feffc2eeeec5bcfac7e34583514e2 Mon Sep 17 00:00:00 2001
+From: Michael Hudson-Doyle <michael.hudson@canonical.com>
+Date: Fri, 31 Jul 2015 11:45:45 +1200
+Subject: [PATCH] runtime: rewrite lfstack packing/unpacking to look more like that in Go
+
+Change-Id: I4ca61240c3f69c6dce1fde8d859f8507dfab80fc
+---
+
+diff --git a/libgo/runtime/lfstack.goc b/libgo/runtime/lfstack.goc
+index 060a0cc..9eb80d9 100644
+--- a/src/libgo/runtime/lfstack.goc
++++ b/src/libgo/runtime/lfstack.goc
+@@ -9,25 +9,41 @@
+ #include "arch.h"
+ 
+ #if __SIZEOF_POINTER__ == 8
+-// Amd64 uses 48-bit virtual addresses, 47-th bit is used as kernel/user flag.
+-// So we use 17msb of pointers as ABA counter.
+-# define PTR_BITS 47
+-#else
+-# define PTR_BITS 32
+-#endif
+-#define PTR_MASK ((1ull<<PTR_BITS)-1)
+-#define CNT_MASK (0ull-1)
+-
+-#if __SIZEOF_POINTER__ == 8 && (defined(__sparc__) || (defined(__sun__) && defined(__amd64__)))
+ // SPARC64 and Solaris on AMD64 uses all 64 bits of virtual addresses.
+ // Use low-order three bits as ABA counter.
+ // http://docs.oracle.com/cd/E19120-01/open.solaris/816-5138/6mba6ua5p/index.html
+-#undef PTR_BITS
+-#undef CNT_MASK
+-#undef PTR_MASK
+-#define PTR_BITS 0
+-#define CNT_MASK 7
+-#define PTR_MASK ((0ull-1)<<3)
++# if defined(__sparc__) || (defined(__sun__) && defined(__amd64__))
++static inline uint64 lfPack(LFNode *node, uintptr cnt) {
++	return ((uint64)(node)) | ((cnt)&7);
++}
++static inline LFNode* lfUnpack(uint64 val) {
++	return (LFNode*)(val&~7);
++}
++# else
++#  if defined(__aarch64__)
++// Depending on the kernel options, pointers on arm64 can have up to 48 significant
++// bits (see https://www.kernel.org/doc/Documentation/arm64/memory.txt).
++#   define PTR_BITS 48
++#  else
++// Amd64 uses 48-bit virtual addresses, 47-th bit is used as kernel/user flag.
++// So we use 17msb of pointers as ABA counter.
++#   define PTR_BITS 47
++#  endif
++# endif
++# define CNT_BITS (64 - PTR_BITS + 3)
++static inline uint64 lfPack(LFNode *node, uintptr cnt) {
++	return ((uint64)(node)<<(64-PTR_BITS)) | (cnt&(((1<<CNT_BITS)-1)));
++}
++static inline LFNode* lfUnpack(uint64 val) {
++	return (LFNode*)((val >> CNT_BITS) << 3);
++}
++#else
++static inline uint64 lfPack(LFNode *node, uintptr cnt) {
++	return ((uint64)(uintptr)(node)<<32) | cnt;
++}
++static inline LFNode* lfUnpack(uint64 val) {
++	return (LFNode*)(uintptr)(val >> 32);
++}
+ #endif
+ 
+ void
+@@ -35,16 +51,16 @@
+ {
+ 	uint64 old, new;
+ 
+-	if((uintptr)node != ((uintptr)node&PTR_MASK)) {
++	if(node != lfUnpack(lfPack(node, 0))) {
+ 		runtime_printf("p=%p\n", node);
+ 		runtime_throw("runtime_lfstackpush: invalid pointer");
+ 	}
+ 
+ 	node->pushcnt++;
+-	new = (uint64)(uintptr)node|(((uint64)node->pushcnt&CNT_MASK)<<PTR_BITS);
++	new = lfPack(node, node->pushcnt);
+ 	for(;;) {
+ 		old = runtime_atomicload64(head);
+-		node->next = (LFNode*)(uintptr)(old&PTR_MASK);
++		node->next = lfUnpack(old);
+ 		if(runtime_cas64(head, old, new))
+ 			break;
+ 	}
+@@ -60,11 +76,11 @@
+ 		old = runtime_atomicload64(head);
+ 		if(old == 0)
+ 			return nil;
+-		node = (LFNode*)(uintptr)(old&PTR_MASK);
++		node = lfUnpack(old);
+ 		node2 = runtime_atomicloadp(&node->next);
+ 		new = 0;
+ 		if(node2 != nil)
+-			new = (uint64)(uintptr)node2|(((uint64)node2->pushcnt&CNT_MASK)<<PTR_BITS);
++			new = lfPack(node2, node2->pushcnt);
+ 		if(runtime_cas64(head, old, new))
+ 			return node;
+ 	}
diff --git a/debian/rules.patch b/debian/rules.patch
index f1975d3..dd98282 100644
--- a/debian/rules.patch
+++ b/debian/rules.patch
@@ -89,6 +89,7 @@ debian_patches += \
 	gccgo-sendfile-fix \
 	pr66368 \
 	pr67280 \
+	pr67508 \
 
 ifeq ($(libstdcxx_abi),new)
   debian_patches += libstdc++-functexcept