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comparison src/share/vm/opto/subnode.cpp @ 212:99bf1609e2a5

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6697236: missing Identity for "(X+Y) - X" into Y Reviewed-by: kvn
author never
date Thu, 12 Jun 2008 09:47:55 -0700
parents ba764ed4b6f2
children 1e026f8da827
comparison
equal deleted inserted replaced
188:c0ecab83e6f3 212:99bf1609e2a5
43 in(2)->Opcode() == Opcode() && 43 in(2)->Opcode() == Opcode() &&
44 phase->type( in(2)->in(1) )->higher_equal( zero ) ) { 44 phase->type( in(2)->in(1) )->higher_equal( zero ) ) {
45 return in(2)->in(2); 45 return in(2)->in(2);
46 } 46 }
47 47
48 // Convert "(X+Y) - Y" into X 48 // Convert "(X+Y) - Y" into X and "(X+Y) - X" into Y
49 if( in(1)->Opcode() == Op_AddI ) { 49 if( in(1)->Opcode() == Op_AddI ) {
50 if( phase->eqv(in(1)->in(2),in(2)) ) 50 if( phase->eqv(in(1)->in(2),in(2)) )
51 return in(1)->in(1); 51 return in(1)->in(1);
52 if (phase->eqv(in(1)->in(1),in(2)))
53 return in(1)->in(2);
54
52 // Also catch: "(X + Opaque2(Y)) - Y". In this case, 'Y' is a loop-varying 55 // Also catch: "(X + Opaque2(Y)) - Y". In this case, 'Y' is a loop-varying
53 // trip counter and X is likely to be loop-invariant (that's how O2 Nodes 56 // trip counter and X is likely to be loop-invariant (that's how O2 Nodes
54 // are originally used, although the optimizer sometimes jiggers things). 57 // are originally used, although the optimizer sometimes jiggers things).
55 // This folding through an O2 removes a loop-exit use of a loop-varying 58 // This folding through an O2 removes a loop-exit use of a loop-varying
56 // value and generally lowers register pressure in and around the loop. 59 // value and generally lowers register pressure in and around the loop.