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	Revert my previous patch to ABCD and fix things the right way. There are two problems addressed	2009-11-09 00:44:44 +00:00
ADCE	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
ArgumentPromotion	Make opt default to not adding a target data string and update tests that depend on target data to supply it within the test	2009-11-03 15:29:06 +00:00
BlockPlacement	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
BranchFolding	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
CodeExtractor	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
CodeGenPrepare	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
ConstantMerge	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
ConstProp	Fix PR5551 by not ignoring the top level constantexpr when	2009-12-04 06:29:29 +00:00
DeadArgElim	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
DeadStoreElimination	Fix some CHECK lines which were ignored by accident.	2009-12-12 09:25:50 +00:00
FunctionAttrs	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
GlobalDCE	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
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	Make getUniqueExitBlocks's precondition assert more precise, to	2009-12-11 20:05:23 +00:00
Inline	implement a nice little efficiency hack in the inliner. Since we're now	2009-11-12 07:56:08 +00:00
InstCombine	Teach instcombine to fold compares of loads from constant	2010-01-02 08:12:04 +00:00
Internalize	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
IPConstantProp	Fix a use of an invalidated iterator in the case where there are multiple	2009-11-23 16:13:39 +00:00
JumpThreading	fix PR5698	2009-12-06 17:17:23 +00:00
LCSSA	Trim a bunch of unneeded code from this testcase.	2009-11-10 01:33:08 +00:00
LICM	Add radar fixed in comment.	2009-12-14 19:07:25 +00:00
LoopDeletion	Make LoopDeletion check the maximum backedge taken count, rather than the	2009-10-23 17:10:01 +00:00
LoopIndexSplit	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
LoopRotate	fix PR5837 by having SSAUpdate reuse phi nodes for the	2009-12-21 07:16:11 +00:00
LoopSimplify	Make Loop::getLoopLatch() work on loops which don't have preheaders, as	2009-11-20 20:51:18 +00:00
LoopStrengthReduce	Generalize OptimizeLoopTermCond to optimize more loop terminating icmp to use postinc iv.	2009-11-17 18:10:11 +00:00
LoopUnroll	Teach getSmallConstantTripMultiple about Shl operators.	2009-11-20 01:09:34 +00:00
LoopUnswitch	Reverting patch in revision 89758, initial attempt at fixing PR5373 has proven to be bogus.	2009-11-25 05:38:41 +00:00
LowerInvoke	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
LowerSetJmp	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
LowerSwitch	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
Mem2Reg	fix a bug exposed by moving SRoA earlier which caused a crash building kc++	2009-11-02 04:37:17 +00:00
MemCpyOpt	Make opt default to not adding a target data string and update tests that depend on target data to supply it within the test	2009-11-03 15:29:06 +00:00
MergeFunc	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
PruneEH	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
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	fix a crash in SCCP handling extractvalue of an array, pointed out and	2009-11-10 22:02:09 +00:00
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	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
SSI	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00
StripSymbols	Update test.	2009-09-09 02:41:50 +00:00
TailCallElim	Improve tail call elimination to handle the switch statement.	2009-11-07 21:10:15 +00:00
TailDup	Change tests from "opt %s" to "opt < %s" so that opt doesn't see the	2009-09-11 18:01:28 +00:00