Bug ID: JDK-6297035 Automatically generated program crashes compiler on all platforms

Type: Bug
Component: hotspot
Sub-Component: compiler
Affected Version: 6

Priority: P2
Status: Closed
Resolution: Fixed
OS: generic,other
CPU: generic,x86

Submitted: 2005-07-14
Updated: 2020-09-14
Resolved: 2005-09-08

JDK 6
6 b51Fixed

The attached automatically generates program crashes server compiler on all platfroms under the following JVMs: 1.4.2, 1.5, 1.6b42.
The test is run with the following command: 
java -server -Xcomp Tester_23
###@###.### 2005-07-14 18:01:06 GMT

SUGGESTED FIX Webrev: http://analemma.sfbay.sun.com/net/prt-archiver.sfbay/data/archived_workspaces/main/c2_baseline/2005/20050825162747.kvn.6297035/workspace/webrevs/webrev-2005.08.25/index.html Fixed 6297035: Automatically generated program crashes compiler on all platforms Fixed 4911139: Runthese -full x86 -server asserts "Identity must clean this up" Fixed 5067347: dead code/loops checks and elimination 1. Check if it is a loop when we about to subsume a phi node with one data input. If it is a loop then replace the phi node with Top node to prevent the creation of a dead loop and phi copy. There are two places were we do this - in RegionNode::Ideal() and PhiNode::Ideal(). In RegionNode::Ideal() after removing dead (null or top) region's inputs we check the case when only one input left (in addition to self reference). The new method PhaseGVN::is_unreachable_region(n) is called to determine if this region is reachable from root. If not - subsume region's phis with Top node to break a dead loop and prevent phi copies creation. Replace reference to the region with Top for all other region's users and remove the region node. In PhiNode::Ideal() phi's inputs could become dead before correspondent region's inputs so we can't use the same method. The new method PhaseGVN::is_unsafe_data_loop(n) is called to determine if this phi references itself directly or through other data nodes. If does - replace the phi with Top to break a dead loop. 2. Add new flag Flag_is_dead_loop_safe to Node::NodeFlags and new method Node::is_dead_loop_safe() for Ideal nodes which could reference itself during GVN transformations or can not be in a loop. For now they are Con, Phi, Proj, CastPP, CheckCastPP nodes. It is safe to replace the phi (with one input) with one of these nodes to reduce the number of graph walks. I mark Phi nodes as safe node not only because they can reference itself but also to prevent mistaking the fallthrough case inside an outer loop as a dead loop when the phi references itselfs through an other phi. 3. Replace all existing dead loop checks in Ideal() methods with asserts. Add new debug method PhaseGVN::dead_loop_check() to check self references for all nodes before the call to Ideal().

26-08-2005

EVALUATION The case of a missing dead loop check. This time in MulNode::Ideal(). ###@###.### 2005-07-15 00:03:40 GMT

15-07-2005

Duplicate :	JDK-6309806 - c2 crashes in optimizer during OSR compilation
Duplicate :	JDK-6301887 - c2 crashes on x86 systems in loop optimization
Relates :	JDK-6371167 - fastdebug c2 fails assertion on x86 platforms: adr_type must match alias idx
Relates :	JDK-8252583 - Clean up unused phi-to-copy degradation mechanism
Relates :	JDK-5067347 - dead code/loops checks and elimination.
Relates :	JDK-6560812 - "must set_type before use" bug in mulnode.cpp