ARM: Fix JIT bug that miscompiles Eclipse

[Andrew Haley]

Eclipse sometimes hangs with the current ARM JIT.  It turns out that we
are corrupting the count operand in

  a << b

If b lives in a local it gets ANDed with 31.  Most shift counts are
less than 31 so it doesn't usually matter.  In Eclipse, though, we
have

   for (int i = 1; i <= 32; i++) {
       if ((sourcePriority & (1 << i)) != 0) {
           ...
       }
   }

This never terminates because each time around the loop i is ANDed
with 31.

I guess that this loop should really be

   for (int i = 0; i < 32; i++) {

i.e. this may be a bug in Eclipse.  But we shouldn't miscompile it.  I
think this bug has been in the ARM JIT for quite a long time.

I also took the opportunity to ask the CompilerOracle which methods
should be JIT-compiled.  This means we now have the flexibility to
disable specific method compilation from the command line.

Andrew.


# HG changeset patch
# User aph
# Date 1338991762 14400
# Node ID 51380f2370a7c982f09dc1070c6c1c66218b5600
# Parent  d1154290751107fc148173d73bc0cdef145f2230
Fix JIT bug that miscompiles org.eclipse.ui.internal.contexts.ContextAuthority.sourceChanged
2012-06-06  Andrew Haley  <aph at redhat.com>

        * thumb2.cpp (Thumb2_Compile): Ask the CompilerOracle if we should
        compile this method.
        (Thumb2_iOp): Use a temporary to hold the shift count.

diff -r d11542907511 -r 51380f2370a7 src/cpu/zero/vm/thumb2.cpp
--- a/src/cpu/zero/vm/thumb2.cpp        Thu May 31 06:42:18 2012 -0400
+++ b/src/cpu/zero/vm/thumb2.cpp        Wed Jun 06 10:09:22 2012 -0400
@@ -68,6 +68,7 @@
 #include <ucontext.h>
 #include "precompiled.hpp"
 #include "interpreter/bytecodes.hpp"
+#include "compiler/compilerOracle.hpp"

 #define opc_nop                        0x00
 #define opc_aconst_null                0x01
@@ -3969,8 +3970,12 @@
   case opc_ishl:
   case opc_ishr:
   case opc_iushr:
-    and_imm(jinfo->codebuf, r_rho, r_rho, 31);
-    break;
+    {
+      unsigned tmp_reg = Thumb2_Tmp(jinfo, 1 << r_lho | 1 << r_rho | 1 << r);
+      and_imm(jinfo->codebuf, tmp_reg, r_rho, 31);
+      r_rho = tmp_reg;
+      break;
+    }
   }
   dop_reg(jinfo->codebuf, dOps[opc-opc_iadd], r, r_lho, r_rho, 0, 0);
 }
@@ -7044,10 +7049,15 @@
   if (!(CPUInfo & ARCH_THUMB2))
        UseCompiler = false;

-  if (!UseCompiler || method->is_not_compilable()) {
-       ic->set(ic->state(), 1);
-       bc->set(ic->state(), 1);
-       return 0;
+  {
+    bool ignore;
+    methodHandle mh(thread, method);
+    if (!UseCompiler || method->is_not_compilable()
+       || CompilerOracle::should_exclude(mh, ignore)) {
+      ic->set(ic->state(), 1);
+      bc->set(ic->state(), 1);
+      return 0;
+    }
   }

   slow_entry = *(unsigned *)method->from_interpreted_entry();