llvm-6502/test/Transforms
Philip Reames 1714ad67bd Refine the notion of MayThrow in LICM to include a header specific version
In LICM, we have a check for an instruction which is guaranteed to execute and thus can't introduce any new faults if moved to the preheader. To handle a function which might unconditionally throw when first called, we check for any potentially throwing call in the loop and give up.

This is unfortunate when the potentially throwing condition is down a rare path. It prevents essentially all LICM of potentially faulting instructions where the faulting condition is checked outside the loop. It also greatly diminishes the utility of loop unswitching since control dependent instructions - which are now likely in the loops header block - will not be lifted by subsequent LICM runs.

define void @nothrow_header(i64 %x, i64 %y, i1 %cond) {
; CHECK-LABEL: nothrow_header
; CHECK-LABEL: entry
; CHECK: %div = udiv i64 %x, %y
; CHECK-LABEL: loop
; CHECK: call void @use(i64 %div)
entry:
  br label %loop
loop: ; preds = %entry, %for.inc
  %div = udiv i64 %x, %y
  br i1 %cond, label %loop-if, label %exit
loop-if:
  call void @use(i64 %div)
  br label %loop
exit:
  ret void
}

The current patch really only helps with non-memory instructions (i.e. divs, etc..) since the maythrow call down the rare path will be considered to alias an otherwise hoistable load.  The one exception is that it does kick in for loads which are known to be invariant without regard to other possible stores, i.e. those marked with either !invarant.load metadata of tbaa 'is constant memory' metadata.

Differential Revision: http://reviews.llvm.org/D6725



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224965 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-29 23:00:57 +00:00
..
ADCE
AddDiscriminators IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
AlignmentFromAssumptions
ArgumentPromotion IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
AtomicExpand/ARM
BBVectorize IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
BranchFolding
CodeExtractor
CodeGenPrepare
ConstantHoisting
ConstantMerge
ConstProp
CorrelatedValuePropagation LazyValueInfo: Actually re-visit partially solved block-values in solveBlockValue() 2014-11-25 17:23:05 +00:00
DeadArgElim IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
DeadStoreElimination IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
EarlyCSE
FunctionAttrs
GCOVProfiling IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
GlobalDCE
GlobalOpt IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
GVN IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
IndVarSimplify Teach ScalarEvolution to exploit min and max expressions when proving 2014-12-15 22:50:15 +00:00
Inline IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
InstCombine Loading from null is valid outside of addrspace 0 2014-12-29 22:46:21 +00:00
InstMerge Added 5 more tests related to sink store revision 224247 2014-12-17 08:12:59 +00:00
InstSimplify InstSimplify: Optimize away pointless comparisons 2014-12-20 03:04:38 +00:00
Internalize
IPConstantProp
JumpThreading IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
LCSSA [LCSSA] Handle PHI insertion in disjoint loops 2014-12-22 22:35:46 +00:00
LICM Refine the notion of MayThrow in LICM to include a header specific version 2014-12-29 23:00:57 +00:00
LoadCombine
LoopDeletion
LoopIdiom IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
LoopReroll
LoopRotate IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
LoopSimplify
LoopStrengthReduce IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
LoopUnroll IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
LoopUnswitch
LoopVectorize Masked Load and Store Intrinsics in loop vectorizer. 2014-12-16 11:50:42 +00:00
LowerAtomic
LowerExpectIntrinsic IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
LowerInvoke
LowerSwitch
Mem2Reg IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
MemCpyOpt
MergeFunc IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
MetaRenamer
ObjCARC IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
PartiallyInlineLibCalls
PhaseOrdering
PruneEH
Reassociate
Reg2Mem
SampleProfile IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
Scalarizer IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
ScalarRepl IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
SCCP
SeparateConstOffsetFromGEP/NVPTX
SimplifyCFG [SimplifyCFG] Revise common code sinking 2014-12-23 08:26:55 +00:00
Sink
SLPVectorizer Revert 224119 "This patch recognizes (+ (+ v0, v1) (+ v2, v3)), reorders them for bundling into vector of loads, 2014-12-17 10:34:27 +00:00
SROA
StripSymbols IR: Make metadata typeless in assembly 2014-12-15 19:07:53 +00:00
StructurizeCFG StructurizeCFG: Use LoopInfo analysis for better loop detection 2014-12-03 04:28:32 +00:00
TailCallElim
TailDup
Util [SwitchLowering] Handle destinations on multiple phi instructions 2014-12-02 18:31:53 +00:00