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  1. JDK
  2. JDK-8256655

rework long counted loop handling

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    • b27

    Description

      Currently the transformation of a long counted loop to a loop nest with an inner int counted loop is performed in 2 steps:

      1- recognize the counted loop shape and build the loop nest
      2- transform the inner loop into a counted loop

      I propose changing this to a 3 steps process:

      1- recognize the counted loop shape (transform the loop into a LongCountedLoop)
      2- build the loop nest
      3- transform the inner loop into a counted loop

      The benefits are:

      - the logic is cleaner because step 1 and 2 are now separated
      - simple optimizations (loop iv type, empty loop elimination, parallel iv) can be implemented for LongCountedLoop by refactoring existing code

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          relates to

          Bug - A problem which impairs or prevents the functions of the product. JDK-8298851 C2: ConvL2I nodes should not be split through phis

          • P3 - Major loss of function.
          • Open

          Bug - A problem which impairs or prevents the functions of the product. JDK-8261308 C2: assert(inner->is_valid_counted_loop(T_INT) && inner->is_strip_mined()) failed: OuterStripMinedLoop should have been removed

          • P3 - Major loss of function.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. JDK-8299259 C2: Div/Mod nodes without zero check could be split through iv phi of loop resulting in SIGFPE

          • P3 - Major loss of function.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. JDK-8263189 C2: assert(!had_error) failed: bad dominance

          • P2 - Crashes, loss of data, severe memory leak.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. JDK-8271203 C2: assert(iff->Opcode() == Op_If || iff->Opcode() == Op_CountedLoopEnd || iff->Opcode() == Op_RangeCheck) failed: Check this code when new subtype is added

          • P3 - Major loss of function.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. JDK-8275854 C2: assert(stride_con != 0) failed: missed some peephole opt

          • P3 - Major loss of function.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. JDK-8277906 Incorrect type for IV phi of long counted loops after CCP

          • P3 - Major loss of function.
          • Resolved

          Bug - A problem which impairs or prevents the functions of the product. JDK-8278790 Inner loop of long loop nest runs for too few iterations

          • P3 - Major loss of function.
          • Resolved

          Enhancement - null JDK-8223051 support loops with long (64b) trip counts

          • P4 - Minor loss of function, or other problem where easy workaround is present.
          • Resolved
          links to

          Commit Commit openjdk/jdk/3d460bd2

          Review Review openjdk/jdk/1316

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              roland Roland Westrelin
              roland Roland Westrelin
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                Updated:
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