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Disable the use of TBAA when using AA in CodeGen

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There are currently two issues, of which I currently know, that prevent TBAA
from being correctly usable in CodeGen:

  1. Stack coloring does not update TBAA when merging allocas. This is easy
     enough to fix, but is not the largest problem.

  2. CGP inserts ptrtoint/inttoptr pairs when sinking address computations.
     Because BasicAA does not handle inttoptr, we'll often miss basic type punning
     idioms that we need to catch so we don't miscompile real-world code (like LLVM).

I don't yet have a small test case for this, but this fixes self hosting a
non-asserts build of LLVM on PPC64 when using -enable-aa-sched-mi and -misched=shuffle.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200093 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel 2014-01-25 19:24:54 +00:00
parent 55604d9716
commit 397cd32bc2
3 changed files with 32 additions and 4 deletions
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13
lib/CodeGen/ScheduleDAGInstrs.cpp
View File

@ -45,6 +45,15 @@ static cl::opt<bool> EnableAASchedMI("enable-aa-sched-mi", cl::Hidden,
cl::ZeroOrMore, cl::init(false),
cl::desc("Enable use of AA during MI GAD construction"));
// FIXME: Enable the use of TBAA. There are two known issues preventing this:
// 1. Stack coloring does not update TBAA when merging allocas
// 2. CGP inserts ptrtoint/inttoptr pairs when sinking address computations.
// Because BasicAA does not handle inttoptr, we'll often miss basic type
// punning idioms that we need to catch so we don't miscompile real-world
// code.
static cl::opt<bool> UseTBAA("use-tbaa-in-sched-mi", cl::Hidden,
cl::init(false), cl::desc("Enable use of TBAA during MI GAD construction"));
ScheduleDAGInstrs::ScheduleDAGInstrs(MachineFunction &mf,
const MachineLoopInfo &mli,
const MachineDominatorTree &mdt,
@ -556,9 +565,9 @@ static bool MIsNeedChainEdge(AliasAnalysis *AA, const MachineFrameInfo *MFI,
AliasAnalysis::AliasResult AAResult = AA->alias(
AliasAnalysis::Location(MMOa->getValue(), Overlapa,
MMOa->getTBAAInfo()),
UseTBAA ? MMOa->getTBAAInfo() : 0),
AliasAnalysis::Location(MMOb->getValue(), Overlapb,
MMOb->getTBAAInfo()));
UseTBAA ? MMOb->getTBAAInfo() : 0));
return (AAResult != AliasAnalysis::NoAlias);
}

16
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -56,6 +56,16 @@ namespace {
CombinerGlobalAA("combiner-global-alias-analysis", cl::Hidden,
cl::desc("Enable DAG combiner's use of IR alias analysis"));
// FIXME: Enable the use of TBAA. There are two known issues preventing this:
// 1. Stack coloring does not update TBAA when merging allocas
// 2. CGP inserts ptrtoint/inttoptr pairs when sinking address computations.
// Because BasicAA does not handle inttoptr, we'll often miss basic type
// punning idioms that we need to catch so we don't miscompile real-world
// code.
static cl::opt<bool>
UseTBAA("combiner-use-tbaa", cl::Hidden, cl::init(false),
cl::desc("Enable DAG combiner's use of TBAA"));
#ifndef NDEBUG
static cl::opt<std::string>
CombinerAAOnlyFunc("combiner-aa-only-func", cl::Hidden,
@ -11079,8 +11089,10 @@ bool DAGCombiner::isAlias(SDValue Ptr1, int64_t Size1, bool IsVolatile1,
int64_t Overlap1 = Size1 + SrcValueOffset1 - MinOffset;
int64_t Overlap2 = Size2 + SrcValueOffset2 - MinOffset;
AliasAnalysis::AliasResult AAResult =
AA.alias(AliasAnalysis::Location(SrcValue1, Overlap1, TBAAInfo1),
AliasAnalysis::Location(SrcValue2, Overlap2, TBAAInfo2));
AA.alias(AliasAnalysis::Location(SrcValue1, Overlap1,
UseTBAA ? TBAAInfo1 : 0),
AliasAnalysis::Location(SrcValue2, Overlap2,
UseTBAA ? TBAAInfo2 : 0));
if (AAResult == AliasAnalysis::NoAlias)
return false;
}

7
lib/CodeGen/StackColoring.cpp
View File

@ -553,6 +553,13 @@ void StackColoring::remapInstructions(DenseMap<int, int> &SlotRemap) {
if (!V)
continue;
// FIXME: In order to enable the use of TBAA when using AA in CodeGen,
// we'll also need to update the TBAA nodes in MMOs with values
// derived from the merged allocas. When doing this, we'll need to use
// the same variant of GetUnderlyingObjects that is used by the
// instruction scheduler (that can look through ptrtoint/inttoptr
// pairs).
// We've replaced IR-level uses of the remapped allocas, so we only
// need to replace direct uses here.
if (!isa<AllocaInst>(V))