RFR: 8302814: Delete unused CountLoopEnd instruct with CmpX [v3]

[SUN Guoyun]

On Thu, 23 Feb 2023 09:34:38 GMT, SUN Guoyun <duke at openjdk.org> wrote:

>> CountLoopEnd only for T_int, therefore the following instructs in riscv.ad are useless and should be deleted.
>> 
>> CountedLoopEnd cmp (CmpL op1 op2)
>> CountedLoopEnd cmp (CmpU op1 op2)
>> CountedLoopEnd cmp (CmpP op1 op2)
>> CountedLoopEnd cmp (CmpN op1 op2)
>> CountedLoopEnd cmp (CmpF op1 op2)
>> CountedLoopEnd cmp (CmpD op1 op2)
>> 
>> and CountedLoopEnd with CmpU on x86*.ad, aarch64.ad ar useless also.
>> 
>> Please help review it.
>> 
>> Thanks.
>
> SUN Guoyun has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8302814: Delete unused CountLoopEnd instruct with CmpX

For bytecodes if_icmpxx(used by java`s for loop)、ifeq/ifne/iflt/ifle/ifgt/ifge, if_icmpxx(used by java`s while loop), C2 compiler created CmpINode not CmpUNode, so I think that should doesn't exist CountedLoopNode with CmpUNode.
<pre><code class="cpp">
// src/hotspot/share/opto/parse2.cpp

2661   case Bytecodes::_ifeq: btest = BoolTest::eq; goto handle_ifxx;                
2662   case Bytecodes::_ifne: btest = BoolTest::ne; goto handle_ifxx;                
2663   case Bytecodes::_iflt: btest = BoolTest::lt; goto handle_ifxx;                
2664   case Bytecodes::_ifle: btest = BoolTest::le; goto handle_ifxx;                
2665   case Bytecodes::_ifgt: btest = BoolTest::gt; goto handle_ifxx;                
2666   case Bytecodes::_ifge: btest = BoolTest::ge; goto handle_ifxx;                
2667   handle_ifxx:                                                                  
2668     // If this is a backwards branch in the bytecodes, add Safepoint            
2669     maybe_add_safepoint(iter().get_dest());                                     
2670     a = _gvn.intcon(0);                                                         
2671     b = pop();                                                                  
2672     c = _gvn.transform( new CmpINode(b, a) );                                   
2673     do_if(btest, c);                                                            
2674     break;                                                                      
2675                                                                                 
2676   case Bytecodes::_if_icmpeq: btest = BoolTest::eq; goto handle_if_icmp;        
2677   case Bytecodes::_if_icmpne: btest = BoolTest::ne; goto handle_if_icmp;        
2678   case Bytecodes::_if_icmplt: btest = BoolTest::lt; goto handle_if_icmp;        
2679   case Bytecodes::_if_icmple: btest = BoolTest::le; goto handle_if_icmp;        
2680   case Bytecodes::_if_icmpgt: btest = BoolTest::gt; goto handle_if_icmp;        
2681   case Bytecodes::_if_icmpge: btest = BoolTest::ge; goto handle_if_icmp;        
2682   handle_if_icmp:                                                               
2683     // If this is a backwards branch in the bytecodes, add Safepoint            
2684     maybe_add_safepoint(iter().get_dest());                                     
2685     a = pop();                                                                  
2686     b = pop();                                                                  
2687     c = _gvn.transform( new CmpINode( b, a ) );  
</code></pre>

-------------

PR: https://git.openjdk.org/jdk/pull/12648