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
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,
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);
}
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,
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;
}
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))