Mercurial > hg > truffle

annotate graal/GraalCompiler/bin/com/sun/c1x/doc/differences.txt @ 2509:16b9a8b5ad39

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Renamings Runtime=>GraalRuntime and Compiler=>GraalCompiler
author Thomas Wuerthinger <thomas@wuerthinger.net>
date Wed, 27 Apr 2011 11:50:44 +0200
parents graal/Compiler/bin/com/sun/c1x/doc/differences.txt@9ec15d6914ca
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
2507
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
1 Differences between C1 and C1X, including upgrades and limitations
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
2 (and some general information about C1)
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
3 ======================================================================
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
4
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
5 StrictFP:
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
6 - C1X has removed the backend code to deal with the FPU stack, and therefore
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
7 requires SSE2 currently. StrictFP is still tracked in the front end.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
8 - C1 will not inline methods with different strictfp-ness. C1X does not have this
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
9 limitation because it only targets SSE2 x86 processors.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
10
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
11 JSR/RET
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
12 - C1 will bail out if it encounters strange JSR/RET patterns
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
13 - recursive JSRs
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
14 - JSR regions that are shared with non-JSR code
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
15 - RET encountered out of JSR (would not verify)
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
16
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
17 Exceptions
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
18 - C1 will bailout if the code of an exception handler can be reached via normal
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
19 control flow.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
20 => C1X might be extended to introduce a phi for the exception
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
21 object in this case.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
22 - C1 will bailout if an exception handler covers itself
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
23
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
24 Verification
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
25 - C1 does not rely on bytecode verification having been run. However, if it detects
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
26 type errors in its building the IR graph it will usually bail out.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
27 - C1 requires a bitmap of the bytecode, where a bit for
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
28 each byte of the bytecode indicates if the bytecode at that location starts a
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
29 basic block. It uses this to construct the basic block list in a single pass.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
30 => Assertion failures and/or bugs in C1X that cause exceptions to be thrown bail out
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
31 the compilation instead of crashing the VM.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
32 => C1X's BlockMap does not computes the basic block starts in one pass over the bytecode
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
33 and one pass over the successor lists.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
34 => C1X computes the "stores in loops" only when loops are encountered in the CFG.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
35 An option can select conservative mode (all locals stored in all loops) trades
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
36 faster parse speed for fewer optimization opportunities
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
37 => C1X includes an IRChecker that typechecks the entire IR and checks for CFG
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
38 consistency that can be run after each pass.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
39
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
40 Constants
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
41 => C1X allows unrestricted use of object constants throughout the code, including
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
42 folding reads of static final fields that reference objects.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
43
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
44 Pinning
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
45 => C1X pins fewer instructions than C1
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
46 ** C1X will eventually allow certain kinds of instructions to float outside the CFG
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
47 and be scheduled with a C2-lite scheduling pass.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
48
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
49 Synchronization
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
50 - C1 will refuse to compile methods with unbalanced synchronization. This property is
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
51 computed by the bytecode verifier and supplied to C1.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
52 ** C1X will not rely on the bytecode verifier to compute this but should do so itself.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
53 => C1 relied on the backend to generate synchronization code for the root method's
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
54 synchronization operations. C1X inserts code into the start block and generates
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
55 and exception handler to do this explicitly.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
56
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
57 Optimizations
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
58 => C1X has many more options to turn on individual passes, parts of passes, approximations,
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
59 etc. It is designed to have three optimization levels:
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
60 0 = super-fast: essentially no optimization
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
61 1 = fast: inlining, constant folding, and local optimizations
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
62 2 = optimized: inlining, constant folding, local and global optimizations, including
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
63 iterative versions of all algorithms
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
64 ** Planned optimizations for C1X that C1 does not have:
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
65 TypeCheckElimination: remove redundant casts and devirtualize more call sites
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
66 ArrayBoundsCheckElimination: remove redundant array bounds checks and/or restructure
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
67 code to deoptimize when bounds checks within loops will fail
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
68 LoopPeeling: replicate the first iteration of a loop
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
69 LoopUnrolling: replicate the body of certain shapes of loops
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
70 LoopInvariantCodeMotion: move invariant code out of a loop
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
71 ProfileGuidedInlining: use receiver method profiles to emit guarded inlines
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
72 ProfileGuidedBlockLayout: use profiling information for code placement
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
73 Peephole: peephole optimize backend output
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
74
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
75 Block Merging
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
76 ** C1X will replace branches to blocks with a single Goto with a branch to the
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
77 block's successor, if the blocks cannot be merged otherwise.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
78
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
79 Constant Folding / Strength reduction
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
80 - C1 had some of its strength reduction logic built into the GraphBuilder because
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
81 the Canonicalizer could not return multiple instructions.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
82 => C1X added this ability, moved the logic to Canonicalizer, and added a few new
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
83 strength reductions.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
84 => C1X should have an interface for doing folding of @FOLD method calls
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
85 => C1X folds many intrinsic operations that don't have side effects
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
86 => C1X folds all the basic floating point operations
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
87 => C1X strength reduces (e >> C >> K) to (e >> (C + K)) when C and K are constant
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
88 => Multiplies of power-of-2 constants are reduced to shifts in the canonicalizer
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
89 (instead of the backend)
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
90 ** C1X will be able to run a global sparse conditional constant propagation phase
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
91 to catch any missed canonicalization opportunities after graph building.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
92
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
93 Switches
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
94 - C1 did not detect back edges in tableswitch/lookupswitch default branches
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
95 => C1X does detect these back edges
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
96 => C1X moved the canonicalization code of 1 and 2 branch switches to canonicalizer,
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
97 where it belongs
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
98
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
99 Inlining
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
100 - C1 cannot inline:
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
101 - native methods (or their stubs), except some intrinsics
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
102 - methods whose class has not been initialized
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
103 - methods with unbalanced monitors
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
104 - methods with JSRs (this is probably technically possible now)
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
105
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
106 - C1 will not inline:
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
107 - methods with exception handlers (optional)
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
108 - synchronized methods (optional)
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
109 - if the maximum inline depth is reached (default = 9)
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
110 - if the maximum recursive inline depth is reached (default = 1)
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
111 - if the callee is larger than the maximum inline size (reduced to 90% at each level, starting at 35)
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
112 - constructors for subclasses of Throwable
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
113 - if the strictfp-ness of the callee is different than the caller (on x87)
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
114 - abstract methods
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
115 - synchronized intrinsics
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
116
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
117 Load/store elimination
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
118 => C1X may eliminate loads of static fields, which C1 did not
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
119 => C1X distinguishes loads/stores to different fields in MemoryBuffer
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
120 => C1X assumes that RiField instances are unique when .isLoaded() is true
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
121
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
122 Local/Global Value Numbering
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
123 => C1X improved local load elimination and no longer value numbers fields, reducing the
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
124 logic necessary in ValueMap, simplifying it and improving its performance.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
125 => C1X reuses the same simplified ValueMap for GVN. Since heap accesses are no longer
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
126 value numbered, the logic to kill values is unnecessary, greatly simplifying
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
127 GVN.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
128 ** A global version of load elimination will compensate for this loss in the future.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
129 => C1X value numbers are always or'd with a high order bit when value numbering is possible
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
130 to prevent value numbering failing if the value number is accidentally 0.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
131
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
132 Nullcheck elimination
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
133 => A new flag, NonNull, indicates instructions that produce values that are guaranteed
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
134 to be non-null (e.g. NewXXX and Local 0, NullCheck). Instructions that require null
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
135 checks check this flag for their inputs in their constructors, eliminating most
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
136 redundant null checks immediately, without requiring the NullCheckEliminator to run.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
137 => C1X uses a more efficient block ordering for null check elimination. The first pass is
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
138 optimistic and attempts to visit the blocks in reverse post-order. For acyclic graphs,
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
139 this almost always succeeds, requiring no iteration. Full iterative data flow analysis
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
140 can be enabled separately. Bitmaps used during the fixpoint calculation are much
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
141 smaller due to local numbering of instructions (as opposed to global IDs).
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
142 ** C1X will recognize If's that check against null and propagate the non-nullness across
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
143 the appropriate branches.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
144
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
145 BlockListBuilder
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
146 - C1 had a vestigial loop map in BlockListBuilder which was not really used.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
147 => C1X does not need to compute a complete loop map in order to do selective phi creation,
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
148 it builds the "storesInLoops" BitMap in BlockMap.
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
149
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
150 Types
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
151 => C1X adds the declared type of method parameters to Local instructions, which
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
152 may help with devirtualization
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
153 => C1X makes local 0 of instance methods non-null at the start
9ec15d6914ca Pull over of compiler from maxine repository.
Thomas Wuerthinger <thomas@wuerthinger.net>
parents:
diff changeset
154