Chris Lattner 7e9b427c87 if an alloca is only ever accessed as a unit, and is accessed with load/store instructions, ... then don't try to decimate it into its individual pieces. This will just make a mess of the IR and is pointless if none of the elements are individually accessed. This was generating really terrible code for std::bitset (PR8980) because it happens to be lowered by clang as an {[8 x i8]} structure instead of {i64}. The testcase now is optimized to: define i64 @test2(i64 %X) { br label %L2 L2: ; preds = %0 ret i64 %X } before we generated: define i64 @test2(i64 %X) { %sroa.store.elt = lshr i64 %X, 56 %1 = trunc i64 %sroa.store.elt to i8 %sroa.store.elt8 = lshr i64 %X, 48 %2 = trunc i64 %sroa.store.elt8 to i8 %sroa.store.elt9 = lshr i64 %X, 40 %3 = trunc i64 %sroa.store.elt9 to i8 %sroa.store.elt10 = lshr i64 %X, 32 %4 = trunc i64 %sroa.store.elt10 to i8 %sroa.store.elt11 = lshr i64 %X, 24 %5 = trunc i64 %sroa.store.elt11 to i8 %sroa.store.elt12 = lshr i64 %X, 16 %6 = trunc i64 %sroa.store.elt12 to i8 %sroa.store.elt13 = lshr i64 %X, 8 %7 = trunc i64 %sroa.store.elt13 to i8 %8 = trunc i64 %X to i8 br label %L2 L2: ; preds = %0 %9 = zext i8 %1 to i64 %10 = shl i64 %9, 56 %11 = zext i8 %2 to i64 %12 = shl i64 %11, 48 %13 = or i64 %12, %10 %14 = zext i8 %3 to i64 %15 = shl i64 %14, 40 %16 = or i64 %15, %13 %17 = zext i8 %4 to i64 %18 = shl i64 %17, 32 %19 = or i64 %18, %16 %20 = zext i8 %5 to i64 %21 = shl i64 %20, 24 %22 = or i64 %21, %19 %23 = zext i8 %6 to i64 %24 = shl i64 %23, 16 %25 = or i64 %24, %22 %26 = zext i8 %7 to i64 %27 = shl i64 %26, 8 %28 = or i64 %27, %25 %29 = zext i8 %8 to i64 %30 = or i64 %29, %28 ret i64 %30 } In this case, instcombine was able to eliminate the nonsense, but in PR8980 enough PHIs are in play that instcombine backs off. It's better to not generate this stuff in the first place. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123571 91177308-0d34-0410-b5e6-96231b3b80d8		2011-01-16 06:18:28 +00:00
..
ADCE.cpp	Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which	2010-10-19 17:21:58 +00:00
BasicBlockPlacement.cpp	Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which	2010-10-19 17:21:58 +00:00
CMakeLists.txt	CMake: Add missing source file.	2011-01-03 02:13:05 +00:00
CodeGenPrepare.cpp	temporarily revert r123526. While working on a follow-on patch I	2011-01-15 07:51:19 +00:00
ConstantProp.cpp	Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which	2010-10-19 17:21:58 +00:00
CorrelatedValuePropagation.cpp	Fix PR8790, another instance where unreachable code can cause instruction simplification to fail,	2010-12-15 00:55:35 +00:00
DCE.cpp	Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which	2010-10-19 17:21:58 +00:00
DeadStoreElimination.cpp	Move Value::getUnderlyingObject to be a standalone	2010-12-15 20:02:24 +00:00
EarlyCSE.cpp	Duncan deftly points out that readnone functions aren't	2011-01-03 23:38:13 +00:00
GEPSplitter.cpp	Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which	2010-10-19 17:21:58 +00:00
GVN.cpp	Remove the PR8954 workaround.	2011-01-11 22:56:41 +00:00
IndVarSimplify.cpp	reduce indentation. Print <nuw> and <nsw> when dumping SCEV AddRec's	2011-01-09 02:16:18 +00:00
JumpThreading.cpp	Fix a bug in the loop in JumpThreading::ProcessThreadableEdges() where it could falsely produce a MultipleDestSentinel value if the first predecessor ended with an 'indirectbr'. If that happened, it caused an unnecessary FindMostPopularDest() call.	2010-12-16 12:16:00 +00:00
LICM.cpp	Generalize LoadAndStorePromoter a bit and switch LICM	2011-01-15 00:12:35 +00:00
LoopDeletion.cpp	Use SmallVector instead of SmallPtrSet and avoid non-deterministic behavior.	2011-01-12 19:12:45 +00:00
LoopIdiomRecognize.cpp	Teach loop-idiom to turn a loop containing a memset into a larger memset	2011-01-04 07:46:33 +00:00
LoopInstSimplify.cpp	LoopInstSimplify preserves LoopSimplify.	2011-01-09 12:35:16 +00:00
LoopRotation.cpp	remove a bogus assertion: the latch block of a loop is not	2011-01-11 07:47:59 +00:00
LoopStrengthReduce.cpp	split dom frontier handling stuff out to its own DominanceFrontier header,	2011-01-02 22:09:33 +00:00
LoopUnrollPass.cpp	random cleanups	2011-01-11 08:00:40 +00:00
LoopUnswitch.cpp	Revamp the ValueMapper interfaces in a couple ways:	2011-01-08 08:15:20 +00:00
LowerAtomic.cpp	Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which	2010-10-19 17:21:58 +00:00
Makefile	make -fno-rtti the default unless a directory builds with REQUIRES_RTTI.	2010-01-24 20:43:08 +00:00
MemCpyOptimizer.cpp	revert 123144, reenabling the rest of memset formation.	2011-01-12 03:25:15 +00:00
Reassociate.cpp	Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which	2010-10-19 17:21:58 +00:00
Reg2Mem.cpp	Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which	2010-10-19 17:21:58 +00:00
Scalar.cpp	split SROA into two passes: one that uses DomFrontiers (-scalarrepl)	2011-01-14 08:13:00 +00:00
ScalarReplAggregates.cpp	if an alloca is only ever accessed as a unit, and is accessed with load/store instructions,	2011-01-16 06:18:28 +00:00
SCCP.cpp	Avoid exponential growth of a table. It feels like	2010-11-30 20:23:21 +00:00
SimplifyCFGPass.cpp	Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which	2010-10-19 17:21:58 +00:00
SimplifyHalfPowrLibCalls.cpp	Zap the last two -Wself-assign warnings in llvm.	2011-01-06 01:33:22 +00:00
SimplifyLibCalls.cpp	SimplifyLibCalls: Use IRBuilder to simplify code.	2010-12-27 00:16:46 +00:00
Sink.cpp	Add helper functions for computing the Location of load, store,	2010-11-11 21:50:19 +00:00
TailDuplication.cpp	Replace calls to ConstantFoldInstruction with calls to SimplifyInstruction	2010-11-23 20:26:33 +00:00
TailRecursionElimination.cpp	Have a few places that want to simplify phi nodes use SimplifyInstruction	2010-11-16 17:41:24 +00:00