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
ADCE
ArgumentPromotion
BlockPlacement
BranchFolding
CodeExtractor
CodeGenPrepare
ConstantMerge
ConstProp
DeadArgElim
DeadStoreElimination
FunctionAttrs
GlobalDCE
GlobalOpt	fix two bogus tests that the asmparser now rejects.	2009-12-30 05:54:51 +00:00
GVN	fix an overly conservative caching issue that caused memdep to	2009-12-19 21:29:22 +00:00
IndVarSimplify
Inline
InstCombine	Teach instcombine to fold compares of loads from constant	2010-01-02 08:12:04 +00:00
Internalize
IPConstantProp
JumpThreading
LCSSA
LICM
LoopDeletion
LoopIndexSplit
LoopRotate	fix PR5837 by having SSAUpdate reuse phi nodes for the	2009-12-21 07:16:11 +00:00
LoopSimplify
LoopStrengthReduce
LoopUnroll
LoopUnswitch
LowerInvoke
LowerSetJmp
LowerSwitch
Mem2Reg
MemCpyOpt
MergeFunc
PruneEH
Reassociate	When factoring multiply expressions across adds, factor both	2010-01-01 01:13:15 +00:00
ScalarRepl	Generalize SROA to allow the first index of a GEP to be non-zero. Add a	2009-12-22 06:57:14 +00:00
SCCP
SimplifyCFG	fix two bogus tests that the asmparser now rejects.	2009-12-30 05:54:51 +00:00
SimplifyLibCalls	move an optimization for memcmp out of simplifylibcalls and into	2009-12-24 00:37:38 +00:00
SRETPromotion
SSI
StripSymbols
TailCallElim
TailDup