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LLVM backend for 6502
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dbaeb6e7cb
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Kevin Qin dbaeb6e7cb Use a loop to simplify the runtime unrolling prologue. 
Runtime unrolling will create a prologue to execute the extra
iterations which is can't divided by the unroll factor. It
generates an if-then-else sequence to jump into a factor -1
times unrolled loop body, like

    extraiters = tripcount % loopfactor
    if (extraiters == 0) jump Loop:
    if (extraiters == loopfactor) jump L1
    if (extraiters == loopfactor-1) jump L2
    ...
    L1:  LoopBody;
    L2:  LoopBody;
    ...
    if tripcount < loopfactor jump End
    Loop:
    ...
    End:

It means if the unroll factor is 4, the loop body will be 7
times unrolled, 3 are in loop prologue, and 4 are in the loop.
This commit is to use a loop to execute the extra iterations
in prologue, like

        extraiters = tripcount % loopfactor
        if (extraiters == 0) jump Loop:
        else jump Prol
 Prol:  LoopBody;
        extraiters -= 1                 // Omitted if unroll factor is 2.
        if (extraiters != 0) jump Prol: // Omitted if unroll factor is 2.
        if (tripcount < loopfactor) jump End
 Loop:
 ...
 End:

Then when unroll factor is 4, the loop body will be copied by
only 5 times, 1 in the prologue loop, 4 in the original loop.
And if the unroll factor is 2, new loop won't be created, just
as the original solution.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218604 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-29 11:15:00 +00:00
autoconf Delete support for AuroraUX. 2014-08-14 15:15:09 +00:00
bindings Reinstate "Nuke the old JIT." 2014-09-02 22:28:02 +00:00
cmake Add LLVM_ENABLE_MODULES flag to CMake to enable building with C++ modules. 2014-09-26 22:40:15 +00:00
docs fix a typo in doumentation index. 2014-09-26 06:59:15 +00:00
examples Add doInitialization/doFinalization to DataLayoutPass. 2014-09-10 21:27:43 +00:00
include Remove dead code from DIBuilder 2014-09-29 06:32:54 +00:00
lib Use a loop to simplify the runtime unrolling prologue. 2014-09-29 11:15:00 +00:00
projects
test Use a loop to simplify the runtime unrolling prologue. 2014-09-29 11:15:00 +00:00
tools llvm-vtabledump: Further simplification 2014-09-26 22:32:19 +00:00
unittests [Support] Add type-safe alternative to llvm::format() 2014-09-25 20:30:58 +00:00
utils Reduce code duplication a bit. 2014-09-27 05:26:42 +00:00
.arcconfig
.clang-format
.clang-tidy Add .clang-tidy configuration file to provide LLVM-optimized defaults for 2014-09-08 13:30:00 +00:00
.gitignore
CMakeLists.txt Add LLVM_ENABLE_MODULES flag to CMake to enable building with C++ modules. 2014-09-26 22:40:15 +00:00
CODE_OWNERS.TXT Add Tom Stellard's role as 3.5 release manager. 2014-09-12 08:07:31 +00:00
configure Delete support for AuroraUX. 2014-08-14 15:15:09 +00:00
CREDITS.TXT Rise from the dead and update personal info 2014-08-25 17:51:04 +00:00
LICENSE.TXT
llvm.spec.in
LLVMBuild.txt
Makefile
Makefile.common
Makefile.config.in
Makefile.rules Revert my earlier change to add "all" as a dependency to check. In 2014-09-19 18:44:27 +00:00
README.txt

README.txt 

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