# HG changeset patch
# User Bernhard Urban <bernhard.urban@jku.at>
# Date 1380526338 -7200
# Node ID 463f51256c86ce1511ec05ea292226ccdcd06a78
# Parent  e1a1264cb0a79638ff0e38d512de5adb6ab0368b
AMD64HotSpot: emit jump to IC miss handler directly instead of emitting it inside verfied_entry

for empty methods we emitted something like this if a inline cache is needed:

    prefix:
        00:    < IC check >
               ...
        0b:    jne <ic_miss_call>
        11:    nop
               ...
    verified_entry:
        20:    ret
    ic_miss_call:
        21:    jmp <entry of runtime function>


when a method is deoptimized, HotSpot patches the verified_entry (0x20) with a
jump to a stub that handles call-sites that has been made non-entrant. since this jump
is 5 bytes long, it will overwrite ic_miss_call and blow up every caller that
calls this method via the unverified entry (prefix).

the fix is to emit the jump to the runtime function inside the unverfied entry:

    prefix:
        00:    < IC check >
               ...
        0b:    je  <verified_entry>
        11:    jeq <entry of runtime function>
        16:    nop
               ...
    verified_entry:
        20:    ret

diff -r e1a1264cb0a7 -r 463f51256c86 graal/com.oracle.graal.hotspot.amd64/src/com/oracle/graal/hotspot/amd64/AMD64HotSpotBackend.java
--- a/graal/com.oracle.graal.hotspot.amd64/src/com/oracle/graal/hotspot/amd64/AMD64HotSpotBackend.java	Mon Sep 30 09:47:41 2013 +0200
+++ b/graal/com.oracle.graal.hotspot.amd64/src/com/oracle/graal/hotspot/amd64/AMD64HotSpotBackend.java	Mon Sep 30 09:32:18 2013 +0200
@@ -236,11 +236,10 @@
         FrameMap frameMap = tasm.frameMap;
         RegisterConfig regConfig = frameMap.registerConfig;
         HotSpotVMConfig config = runtime().config;
-        Label unverifiedStub = installedCodeOwner == null || isStatic(installedCodeOwner.getModifiers()) ? null : new Label();
+        Label verifiedStub = new Label();
 
         // Emit the prefix
-
-        if (unverifiedStub != null) {
+        if (installedCodeOwner != null && !isStatic(installedCodeOwner.getModifiers())) {
             tasm.recordMark(Marks.MARK_UNVERIFIED_ENTRY);
             CallingConvention cc = regConfig.getCallingConvention(JavaCallee, null, new JavaType[]{runtime().lookupJavaType(Object.class)}, target, false);
             Register inlineCacheKlass = rax; // see definition of IC_Klass in
@@ -257,11 +256,13 @@
             } else {
                 asm.cmpq(inlineCacheKlass, src);
             }
-            asm.jcc(ConditionFlag.NotEqual, unverifiedStub);
+            asm.jcc(ConditionFlag.Equal, verifiedStub);
+            AMD64Call.directJmp(tasm, asm, runtime().lookupForeignCall(IC_MISS_HANDLER));
         }
 
         asm.align(config.codeEntryAlignment);
         tasm.recordMark(Marks.MARK_OSR_ENTRY);
+        asm.bind(verifiedStub);
         tasm.recordMark(Marks.MARK_VERIFIED_ENTRY);
 
         // Emit code for the LIR
@@ -278,10 +279,5 @@
             // it has no calls that can cause such "return" entries
             assert !frameMap.accessesCallerFrame() : lirGen.getGraph();
         }
-
-        if (unverifiedStub != null) {
-            asm.bind(unverifiedStub);
-            AMD64Call.directJmp(tasm, asm, runtime().lookupForeignCall(IC_MISS_HANDLER));
-        }
     }
 }