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LLVM backend for 6502
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Michael Gottesman 0b5fad68b2 Teach simplify-cfg how to correctly create covered lookup tables for switches on iN with N >= 3. 
One optimization simplify-cfg performs is the converting of switches to
lookup tables if the switch has > 4 cases. This is done by:

1. Finding the max/min case value and calculating the switch case range.
2. Create a lookup table basic block.
3. Perform a check in the switch's BB to see if the input value is in
the switch's case range. If the input value satisfies said predicate
branch to the lookup table BB, otherwise branch to the switch's default
destination BB using the default value as the result.

The conditional check consists of subtracting the min case value of the
table from any input iN value and then ensuring that said value is
unsigned less than the size of the lookup table represented as an iN
value.

If the lookup table is a covered lookup table, the size of the table will be N
which is 0 as an iN value. Thus the comparison will be an `icmp ult` of an iN
value against 0 which is always false yielding the incorrect result.

This patch fixes this problem by recognizing if we have a covered lookup table
and if we do, unconditionally jumps to the lookup table BB since the covering
property of the lookup table implies no input values could not be handled by
said BB.

rdar://15268442

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193045 91177308-0d34-0410-b5e6-96231b3b80d8
2013-10-20 07:04:37 +00:00
autoconf Update so that it uses the `-V' command line option and supports Python 3.x. 2013-10-12 08:42:59 +00:00
bindings [python-bindings] Added support for getting/setting operands of values and getting the number of operands of a value. 2013-09-11 01:38:12 +00:00
cmake Remove NDBEUG from all release types compile flags. 2013-10-19 07:30:37 +00:00
docs Write a simple description of the 'target triple' directive. This should be expanded. PR8976. 2013-10-18 23:41:25 +00:00
examples Add missing #include's to cctype when using isdigit/alpha/etc. 2013-10-12 00:55:57 +00:00
include [Support][YAML] Add support for accessing tags and tag handle substitution. 2013-10-18 22:38:04 +00:00
lib Teach simplify-cfg how to correctly create covered lookup tables for switches on iN with N >= 3. 2013-10-20 07:04:37 +00:00
projects Revert "Revert "Windows: Add support for unicode command lines"" 2013-10-07 01:00:07 +00:00
test Teach simplify-cfg how to correctly create covered lookup tables for switches on iN with N >= 3. 2013-10-20 07:04:37 +00:00
tools Check for errors when calling lto_codegen_add_module in the gold plugin. 2013-10-18 19:32:06 +00:00
unittests DIEHash: Support for simple (non-recursive, non-reused) type references 2013-10-17 22:07:09 +00:00
utils Typo. 2013-10-20 03:19:25 +00:00
.arcconfig Add .arcconfig to the repository. Useful if someone wants to use phabricator's command line tool. 2012-12-01 12:07:58 +00:00
.clang-format Add a clang-format file so that the tool can automatically detect the 2013-09-02 07:19:04 +00:00
.gitignore Add extra vim swap file pattern 2012-10-09 23:48:34 +00:00
CMakeLists.txt CMake: set stack size for MSVC in just one place 2013-10-17 18:39:47 +00:00
CODE_OWNERS.TXT Add more owners to CODE_OWNERS.TXT (Kostya Serebryany: AddressSanitizer and ThreadSanitizer; Evgeniy Stepanov: MemorySanitizer) 2013-06-27 08:47:12 +00:00
configure Update so that it uses the `-V' command line option and supports Python 3.x. 2013-10-12 08:42:59 +00:00
CREDITS.TXT Update. 2013-09-27 20:40:40 +00:00
LICENSE.TXT Be more specific and capitalize filenames. 2013-05-21 21:22:34 +00:00
llvm.spec.in
LLVMBuild.txt Remove the very substantial, largely unmaintained legacy PGO 2013-10-02 15:42:23 +00:00
Makefile Remove the very substantial, largely unmaintained legacy PGO 2013-10-02 15:42:23 +00:00
Makefile.common Makefile.common: Update a description, s/Source/SOURCES/ , according to MakefileGuide.html#control-variables . 2012-12-07 01:43:23 +00:00
Makefile.config.in Add an autoconf option for turning on -gsplit-dwarf by default 2013-06-25 01:12:25 +00:00
Makefile.rules Makefile.rules: Avoid -fomit-frame-pointer also on cygwin due to PR14646. 2013-08-18 03:38:40 +00:00
README.txt Revert "Test commit to check e-mail address. Please discard this." 2013-10-04 10:59:13 +00:00

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