[RFC] Patch to fix register allocation (PR680)

[Deepak Bhole]

Hi,

I have put all the details in PR680:
http://icedtea.classpath.org/bugzilla/show_bug.cgi?id=680

To summarize, the current inline assembly code in
release_store_fence(volatile jbyte*  p, jbyte  v) is using an incorrect
output operand. It works with the current gcc by pure luck, but with gcc
4.6, it fails.

Attached patches for icedtea6 and icedtea7 fix the issue. I have also
tested this with icedtea6+hs20 and there were no issues.

Thanks to Jakub Jelinek for help with the issue.

IcedTea6 ChangeLog:
2011-03-25  Deepak Bhole <dbhole at redhat.com>

    PR680: Register allocation in release_store_fence(jbyte*, jbyte) is
    incorrect
    * Makefile.am: Apply new pr680-gcc-register-allocation-fix.patch patch.
    * NEWS: Updated
    * patches/pr680-gcc-register-allocation-fix.patch: New patch. Fixes
    register allocation by constraining output to one of a/b/c/d registers.

IcedTea7 ChangeLog:
2011-03-25  Deepak Bhole <dbhole at redhat.com>

    PR680: Register allocation in release_store_fence(jbyte*, jbyte) is
    incorrect
    * Makefile.am: Apply new icedtea-pr680-gcc-register-allocation-fix.patch
    patch.
    * NEWS: Updated
    * patches/icedtea-pr680-gcc-register-allocation-fix.patch: New patch. 
    Fixes register allocation by constraining output to one of a/b/c/d
    registers.

In addition to the tips, I would also recommend this for 1.10 since gcc 4.6
will be out soon and 1.10 will be the stable release for the next little while.

Okay to commit?

Cheers,
Deepak
-------------- next part --------------
diff -r 8c01fdae79ef Makefile.am
--- a/Makefile.am	Fri Mar 25 13:44:12 2011 +0100
+++ b/Makefile.am	Fri Mar 25 19:07:42 2011 -0400
@@ -331,7 +331,8 @@
 	patches/openjdk/7027667-AAShapePipeRegTest.patch \
 	patches/openjdk/7019861-AA-regression-fix.patch \
 	patches/openjdk/6768387-jtable_not_serializable.patch \
-	patches/mark_sun_toolkit_privileged_code.patch
+	patches/mark_sun_toolkit_privileged_code.patch \
+	patches/pr680-gcc-register-allocation-fix.patch
 
 if WITH_ALT_HSBUILD
 ICEDTEA_PATCHES += \
diff -r 8c01fdae79ef NEWS
--- a/NEWS	Fri Mar 25 13:44:12 2011 +0100
+++ b/NEWS	Fri Mar 25 19:07:42 2011 -0400
@@ -20,6 +20,7 @@
     make check jtreg_checks="langtools hotspot".
     If none is provided make check runs all testsuites.
   - Fixed AccessControlContext which was thrown while working with Color class in a PropertyEditor
+  - PR680: Register allocation in release_store_fence(jbyte*, jbyte) is incorrect
 * CACAO
   - Ignore all unknown options, but report them.
   - Fixes build for newer gcc (at least 4.4) on PPC64, breaks older gcc.
diff -r 8c01fdae79ef patches/pr680-gcc-register-allocation-fix.patch
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/patches/pr680-gcc-register-allocation-fix.patch	Fri Mar 25 19:07:42 2011 -0400
@@ -0,0 +1,12 @@
+diff -ur openjdk.orig/hotspot/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp openjdk/hotspot/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp
+--- openjdk.orig/hotspot/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp	2011-02-28 11:03:15.000000000 -0500
++++ openjdk/hotspot/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp	2011-03-25 16:15:31.461400000 -0400
+@@ -148,7 +148,7 @@
+ // Must duplicate definitions instead of calling store_fence because we don't want to cast away volatile.
+ inline void     OrderAccess::release_store_fence(volatile jbyte*  p, jbyte  v) {
+   __asm__ volatile (  "xchgb (%2),%0"
+-                    : "=r" (v)
++                    : "=q" (v)
+                     : "0" (v), "r" (p)
+                     : "memory");
+ }
-------------- next part --------------
diff -r eeb7d84e7ae5 Makefile.am
--- a/Makefile.am	Mon Mar 21 20:47:22 2011 +0000
+++ b/Makefile.am	Fri Mar 25 19:07:13 2011 -0400
@@ -281,7 +281,8 @@
 	patches/parisc.patch \
 	patches/sh4-support.patch \
 	patches/jtreg-httpTest.patch \
-	patches/icedtea-update-bootclasspath.patch
+	patches/icedtea-update-bootclasspath.patch \
+	patches/icedtea-pr680-gcc-register-allocation-fix.patch
 
 # Conditional patches
 
diff -r eeb7d84e7ae5 NEWS
--- a/NEWS	Mon Mar 21 20:47:22 2011 +0000
+++ b/NEWS	Fri Mar 25 19:07:13 2011 -0400
@@ -6,6 +6,8 @@
   - Match Shark in icedtea6, makes OSR work by removing vestigal check.
   - LLVM 2.7 non-product fixes.
   - Correct suffix for the llvm.atomic.cmp.swap intrinsic.
+* Bug fixes
+  - PR680: Register allocation in release_store_fence(jbyte*, jbyte) is incorrect
 
 New in release 1.13 (2010-07-29)
 
diff -r eeb7d84e7ae5 patches/icedtea-pr680-gcc-register-allocation-fix.patch
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/patches/icedtea-pr680-gcc-register-allocation-fix.patch	Fri Mar 25 19:07:13 2011 -0400
@@ -0,0 +1,12 @@
+diff -ur openjdk.orig/hotspot/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp openjdk/hotspot/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp
+--- openjdk.orig/hotspot/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp	2011-02-28 11:03:15.000000000 -0500
++++ openjdk/hotspot/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp	2011-03-25 16:15:31.461400000 -0400
+@@ -148,7 +148,7 @@
+ // Must duplicate definitions instead of calling store_fence because we don't want to cast away volatile.
+ inline void     OrderAccess::release_store_fence(volatile jbyte*  p, jbyte  v) {
+   __asm__ volatile (  "xchgb (%2),%0"
+-                    : "=r" (v)
++                    : "=q" (v)
+                     : "0" (v), "r" (p)
+                     : "memory");
+ }