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comparison src/share/vm/opto/matcher.hpp @ 1575:3657cb01ffc5

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6954029: Improve implicit null check generation with compressed oops Summary: Hoist DecodeN instruction above null check Reviewed-by: never, twisti
author kvn
date Wed, 02 Jun 2010 09:49:32 -0700
parents 2883969d09e7
children e9ff18c4ace7
comparison
equal deleted inserted replaced
1574:1eb493f33423 1575:3657cb01ffc5
350 // Should the Matcher clone shifts on addressing modes, expecting them to 350 // Should the Matcher clone shifts on addressing modes, expecting them to
351 // be subsumed into complex addressing expressions or compute them into 351 // be subsumed into complex addressing expressions or compute them into
352 // registers? True for Intel but false for most RISCs 352 // registers? True for Intel but false for most RISCs
353 static const bool clone_shift_expressions; 353 static const bool clone_shift_expressions;
354 354
355 static bool narrow_oop_use_complex_address();
356
357 // Generate implicit null check for narrow oops if it can fold
358 // into address expression (x64).
359 //
360 // [R12 + narrow_oop_reg<<3 + offset] // fold into address expression
361 // NullCheck narrow_oop_reg
362 //
363 // When narrow oops can't fold into address expression (Sparc) and
364 // base is not null use decode_not_null and normal implicit null check.
365 // Note, decode_not_null node can be used here since it is referenced
366 // only on non null path but it requires special handling, see
367 // collect_null_checks():
368 //
369 // decode_not_null narrow_oop_reg, oop_reg // 'shift' and 'add base'
370 // [oop_reg + offset]
371 // NullCheck oop_reg
372 //
373 // With Zero base and when narrow oops can not fold into address
374 // expression use normal implicit null check since only shift
375 // is needed to decode narrow oop.
376 //
377 // decode narrow_oop_reg, oop_reg // only 'shift'
378 // [oop_reg + offset]
379 // NullCheck oop_reg
380 //
381 inline static bool gen_narrow_oop_implicit_null_checks() {
382 return Universe::narrow_oop_use_implicit_null_checks() &&
383 (narrow_oop_use_complex_address() ||
384 Universe::narrow_oop_base() != NULL);
385 }
386
355 // Is it better to copy float constants, or load them directly from memory? 387 // Is it better to copy float constants, or load them directly from memory?
356 // Intel can load a float constant from a direct address, requiring no 388 // Intel can load a float constant from a direct address, requiring no
357 // extra registers. Most RISCs will have to materialize an address into a 389 // extra registers. Most RISCs will have to materialize an address into a
358 // register first, so they may as well materialize the constant immediately. 390 // register first, so they may as well materialize the constant immediately.
359 static const bool rematerialize_float_constants; 391 static const bool rematerialize_float_constants;