JDK-7063629 : use cbcond in C2 generated code on T4
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: hs22
  • Priority: P4
  • Status: Closed
  • Resolution: Fixed
  • OS: generic
  • CPU: sparc
  • Submitted: 2011-07-07
  • Updated: 2014-03-25
  • Resolved: 2011-09-30
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JDK 7 JDK 8 Other
7u2Fixed 8Fixed hs22Fixed
Related Reports
Cloners :  
JDK-8038297 - Avoid placing CTI immediately following cbcond instruction on T4
Relates :  
JDK-7079317 - Incorrect branch's destination block in PrintoOptoAssembly output
Relates :  
JDK-7080431 - VM asserts if specified size(x) in .ad is larger than emitted size
Relates :  
JDK-8035283 - Second phase of branch shortening doesn't account for loop alignment
Relates :  
JDK-7063628 - Use cbcond on T4
Relates :  
JDK-7085137 - -XX:+VerifyOops is broken
Description
T4 has new short branch instruction without delay slot. Use it in C2 generated code.
Comments
EVALUATION See main CR
12-09-2011
EVALUATION http://hg.openjdk.java.net/hsx/hotspot-rt/hotspot/rev/95134e034042
23-08-2011
PUBLIC COMMENTS Added new fused compare and branch instructions into sparc.ad and corresponding short versions which use cbcond instruction. Added new flag avoid_back_to_back to avoid generation of cbcond back to back. Split shorten_branches() into 2 methods. First method conservatively estimates code size and branches location and does few rounds of branch shortening. It is executed before ScheduleAndBundle(). Step 3 is moved to new method shorten_branches_final() called after ScheduleAndBundle(). It does final paddings, alignment and final branch replacement. Method fill_buffer() does verification instead of padding. Labels are binded now only during code generation in fill_buffer(). As result they are not available when forward branches are emitted. To fix that MacroAssembler branch instructions are used now in x86 .ad files. I replaced unused rtype parameter with maybe_short flag to force using only long branches in .ad long branch instructions. Added check to adlc to verify that short version of a branch instructions has the same declaration in .ad file. Added assert to verify that the size of emitted instruction matches the value returned by MachNode::size(). Found that MachBreakpointNode::size() returned incorrect value on x64. Fixed loop alignment for Sparc (min alignment should be instruction size which is 4 bytes instead of 1 byte). The prototype was done by Tom and I took some of his additional fixes. The block changes go with some code in output to put opto assembly style block comments in the PrintNMethods output. There's also snippet in there that deals with the fact kill projections on branches make it appear the kill occurs after the branch instead of being part of it.
12-08-2011
EVALUATION http://hg.openjdk.java.net/hsx/hotspot-comp/hotspot/rev/95134e034042
12-08-2011