Chris Lattner 1f12e44b62 Teach instcombine to fold compares of loads from constant ... arrays with variable indices into a comparison of the index with a constant. The most common occurrence of this that I see by far is stuff like: if ("foobar"[i] == '\0') ... which we compile into: if (i == 6), saving a load and materialization of the global address. This also exposes loop trip count information to later passes in many cases. This triggers hundreds of times in xalancbmk, which is where I first noticed it, but it also triggers in many other apps. Here are a few interesting ones from various apps: @must_be_connected_without = internal constant [8 x i8*] [i8* getelementptr inbounds ([3 x i8]* @.str64320, i64 0, i64 0), i8* getelementptr inbounds ([3 x i8]* @.str27283, i64 0, i64 0), i8* getelementptr inbounds ([4 x i8]* @.str71327, i64 0, i64 0), i8* getelementptr inbounds ([4 x i8]* @.str72328, i64 0, i64 0), i8* getelementptr inbounds ([3 x i8]* @.str18274, i64 0, i64 0), i8* getelementptr inbounds ([6 x i8]* @.str11267, i64 0, i64 0), i8* getelementptr inbounds ([3 x i8]* @.str32288, i64 0, i64 0), i8* null], align 32 ; <[8 x i8*]*> [#uses=2] %scevgep.i = getelementptr [8 x i8*]* @must_be_connected_without, i64 0, i64 %indvar.i ; <i8**> [#uses=1] %17 = load ... %18 = icmp eq i8* %17, null ; <i1> [#uses=1] -> icmp eq i64 %indvar.i, 7 @yytable1095 = internal constant [84 x i8] c"\12\01(\05\06\07\08\09\0A\0B\0C\0D\0E1\0F\10\11266\1D: \10\11,-,0\03'\10\11B6\04\17&\18\1945\05\06\07\08\09\0A\0B\0C\0D\0E\1E\0F\10\11*\1A\1B\1C$3+>#%;<IJ=ADFEGH9KL\00\00\00C", align 32 ; <[84 x i8]*> [#uses=2] %57 = getelementptr inbounds [84 x i8]* @yytable1095, i64 0, i64 %56 ; <i8*> [#uses=1] %mode.0.in = getelementptr inbounds [9 x i32]* @mb_mode_table, i64 0, i64 %.pn ; <i32*> [#uses=1] load ... %64 = icmp eq i8 %58, 4 ; <i1> [#uses=1] -> icmp eq i64 %.pn, 35 ; <i1> [#uses=0] @gsm_DLB = internal constant [4 x i16] [i16 6554, i16 16384, i16 26214, i16 32767] %scevgep.i = getelementptr [4 x i16]* @gsm_DLB, i64 0, i64 %indvar.i ; <i16*> [#uses=1] %425 = load %scevgep.i %426 = icmp eq i16 %425, -32768 ; <i1> [#uses=0] -> false git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92411 91177308-0d34-0410-b5e6-96231b3b80d8		2010-01-02 08:12:04 +00:00
..
ABCD.cpp
ADCE.cpp
BasicBlockPlacement.cpp
CMakeLists.txt
CodeGenPrepare.cpp	Revert 91280-91283, 91286-91289, 91291, 91293, 91295-91296. It apparently introduced a non-deterministic behavior in the optimizer somewhere.	2009-12-17 09:39:49 +00:00
ConstantProp.cpp
DCE.cpp
DeadStoreElimination.cpp
GEPSplitter.cpp
GVN.cpp	split code that doesn't need to be templated out of IRBuilder into a new	2009-12-28 21:28:46 +00:00
IndVarSimplify.cpp	Add Loop contains utility methods for testing whether a loop	2009-12-18 01:24:09 +00:00
InstructionCombining.cpp	Teach instcombine to fold compares of loads from constant	2010-01-02 08:12:04 +00:00
JumpThreading.cpp	Metadata.h doesn't need to include ValueHandle.h anymore.	2009-12-28 08:20:46 +00:00
LICM.cpp	Add Loop contains utility methods for testing whether a loop	2009-12-18 01:24:09 +00:00
LoopDeletion.cpp
LoopIndexSplit.cpp	Add Loop contains utility methods for testing whether a loop	2009-12-18 01:24:09 +00:00
LoopRotation.cpp
LoopStrengthReduce.cpp	Remove dump routine and the associated Debug.h from a header. Patch up	2009-12-23 22:58:38 +00:00
LoopUnrollPass.cpp
LoopUnswitch.cpp	Add Loop contains utility methods for testing whether a loop	2009-12-18 01:24:09 +00:00
Makefile
MemCpyOptimizer.cpp
Reassociate.cpp	When factoring multiply expressions across adds, factor both	2010-01-01 01:13:15 +00:00
Reg2Mem.cpp
Scalar.cpp
ScalarReplAggregates.cpp	Fix the Convert to scalar to not insert dead loads in the store case. The	2009-12-22 19:33:28 +00:00
SCCP.cpp
SCCVN.cpp	Eliminte unnecessary uses of <cstdio>.	2009-12-18 03:25:51 +00:00
SimplifyCFGPass.cpp	Implement PR5795 by merging duplicated return blocks. This could go further	2009-12-22 06:07:30 +00:00
SimplifyHalfPowrLibCalls.cpp	improve portability to avoid conflicting with std::next in c++'0x.	2009-12-03 00:50:42 +00:00
SimplifyLibCalls.cpp	move an optimization for memcmp out of simplifylibcalls and into	2009-12-24 00:37:38 +00:00
TailDuplication.cpp
TailRecursionElimination.cpp