[llvm] r282520 - [RDF] Add "dead" flag to node attributes
Krzysztof Parzyszek via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 27 11:24:34 PDT 2016
Author: kparzysz
Date: Tue Sep 27 13:24:33 2016
New Revision: 282520
URL: http://llvm.org/viewvc/llvm-project?rev=282520&view=rev
Log:
[RDF] Add "dead" flag to node attributes
Modified:
llvm/trunk/lib/Target/Hexagon/RDFGraph.cpp
llvm/trunk/lib/Target/Hexagon/RDFGraph.h
llvm/trunk/lib/Target/Hexagon/RDFLiveness.cpp
Modified: llvm/trunk/lib/Target/Hexagon/RDFGraph.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Hexagon/RDFGraph.cpp?rev=282520&r1=282519&r2=282520&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Hexagon/RDFGraph.cpp (original)
+++ llvm/trunk/lib/Target/Hexagon/RDFGraph.cpp Tue Sep 27 13:24:33 2016
@@ -65,6 +65,8 @@ raw_ostream &operator<< (raw_ostream &OS
case NodeAttrs::Ref:
if (Flags & NodeAttrs::Undef)
OS << '/';
+ if (Flags & NodeAttrs::Dead)
+ OS << '\\';
if (Flags & NodeAttrs::Preserving)
OS << '+';
if (Flags & NodeAttrs::Clobbering)
@@ -1316,7 +1318,8 @@ void DataFlowGraph::buildStmt(NodeAddr<B
while (uint16_t R = *ImpU++)
ImpUses.insert({R, 0});
- bool NeedsImplicit = isCall(In) || In.isInlineAsm() || In.isReturn();
+ bool IsCall = isCall(In);
+ bool NeedsImplicit = IsCall || In.isInlineAsm() || In.isReturn();
bool IsPredicated = TII.isPredicated(In);
unsigned NumOps = In.getNumOperands();
@@ -1342,6 +1345,8 @@ void DataFlowGraph::buildStmt(NodeAddr<B
Flags |= NodeAttrs::Clobbering;
if (TOI.isFixedReg(In, OpN))
Flags |= NodeAttrs::Fixed;
+ if (IsCall && Op.isDead())
+ Flags |= NodeAttrs::Dead;
NodeAddr<DefNode*> DA = newDef(SA, Op, Flags);
SA.Addr->addMember(DA, *this);
DoneDefs.insert(RR);
@@ -1369,6 +1374,8 @@ void DataFlowGraph::buildStmt(NodeAddr<B
Flags |= NodeAttrs::Clobbering;
if (TOI.isFixedReg(In, OpN))
Flags |= NodeAttrs::Fixed;
+ if (IsCall && Op.isDead())
+ Flags |= NodeAttrs::Dead;
NodeAddr<DefNode*> DA = newDef(SA, Op, Flags);
SA.Addr->addMember(DA, *this);
DoneDefs.insert(RR);
Modified: llvm/trunk/lib/Target/Hexagon/RDFGraph.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Hexagon/RDFGraph.h?rev=282520&r1=282519&r2=282520&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Hexagon/RDFGraph.h (original)
+++ llvm/trunk/lib/Target/Hexagon/RDFGraph.h Tue Sep 27 13:24:33 2016
@@ -191,6 +191,13 @@
// imply that the use in (3) may indeed be reached by some prior def.
// Adding Undef flag to the def in (1) prevents that. The Undef flag
// may be applied to both defs and uses.
+// - Dead: applies only to defs. The value coming out of a "dead" def is
+// assumed to be unused, even if the def appears to be reaching other defs
+// or uses. The motivation for this flag comes from dead defs on function
+// calls: there is no way to determine if such a def is dead without
+// analyzing the target's ABI. Hence the graph should contain this info,
+// as it is unavailable otherwise. On the other hand, a def without any
+// uses on a typical instruction is not the intended target for this flag.
//
// *** Shadow references
//
@@ -261,14 +268,15 @@ namespace rdf {
Block = 0x0005 << 2, // 101
Func = 0x0006 << 2, // 110
- // Flags: 6 bits for now
- FlagMask = 0x003F << 5,
- Shadow = 0x0001 << 5, // 000001, Has extra reaching defs.
- Clobbering = 0x0002 << 5, // 000010, Produces unspecified values.
- PhiRef = 0x0004 << 5, // 000100, Member of PhiNode.
- Preserving = 0x0008 << 5, // 001000, Def can keep original bits.
- Fixed = 0x0010 << 5, // 010000, Fixed register.
- Undef = 0x0020 << 5, // 100000, Has no pre-existing value.
+ // Flags: 7 bits for now
+ FlagMask = 0x007F << 5,
+ Shadow = 0x0001 << 5, // 0000001, Has extra reaching defs.
+ Clobbering = 0x0002 << 5, // 0000010, Produces unspecified values.
+ PhiRef = 0x0004 << 5, // 0000100, Member of PhiNode.
+ Preserving = 0x0008 << 5, // 0001000, Def can keep original bits.
+ Fixed = 0x0010 << 5, // 0010000, Fixed register.
+ Undef = 0x0020 << 5, // 0100000, Has no pre-existing value.
+ Dead = 0x0040 << 5, // 1000000, Does not define a value.
};
static uint16_t type(uint16_t T) { return T & TypeMask; }
Modified: llvm/trunk/lib/Target/Hexagon/RDFLiveness.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Hexagon/RDFLiveness.cpp?rev=282520&r1=282519&r2=282520&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Hexagon/RDFLiveness.cpp (original)
+++ llvm/trunk/lib/Target/Hexagon/RDFLiveness.cpp Tue Sep 27 13:24:33 2016
@@ -86,9 +86,18 @@ namespace rdf {
NodeList Liveness::getAllReachingDefs(RegisterRef RefRR,
NodeAddr<RefNode*> RefA, bool FullChain, const RegisterSet &DefRRs) {
+ NodeList RDefs; // Return value.
SetVector<NodeId> DefQ;
SetVector<NodeId> Owners;
+ // Dead defs will be treated as if they were live, since they are actually
+ // on the data-flow path. They cannot be ignored because even though they
+ // do not generate meaningful values, they still modify registers.
+
+ // If the reference is undefined, there is nothing to do.
+ if (RefA.Addr->getFlags() & NodeAttrs::Undef)
+ return RDefs;
+
// The initial queue should not have reaching defs for shadows. The
// whole point of a shadow is that it will have a reaching def that
// is not aliased to the reaching defs of the related shadows.
@@ -186,7 +195,6 @@ NodeList Liveness::getAllReachingDefs(Re
// covered if we added A first, and A would be covered
// if we added B first.
- NodeList RDefs;
RegisterSet RRs = DefRRs;
auto DefInSet = [&Defs] (NodeAddr<RefNode*> TA) -> bool {
@@ -223,6 +231,11 @@ NodeList Liveness::getAllReachingDefs(Re
}
}
+ auto DeadP = [](const NodeAddr<DefNode*> DA) -> bool {
+ return DA.Addr->getFlags() & NodeAttrs::Dead;
+ };
+ RDefs.resize(std::distance(RDefs.begin(), remove_if(RDefs, DeadP)));
+
return RDefs;
}
@@ -285,7 +298,9 @@ NodeSet Liveness::getAllReachedUses(Regi
return Uses;
// Add all directly reached uses.
- NodeId U = DefA.Addr->getReachedUse();
+ // If the def is dead, it does not provide a value for any use.
+ bool IsDead = DefA.Addr->getFlags() & NodeAttrs::Dead;
+ NodeId U = !IsDead ? DefA.Addr->getReachedUse() : 0;
while (U != 0) {
auto UA = DFG.addr<UseNode*>(U);
if (!(UA.Addr->getFlags() & NodeAttrs::Undef)) {
@@ -296,7 +311,7 @@ NodeSet Liveness::getAllReachedUses(Regi
U = UA.Addr->getSibling();
}
- // Traverse all reached defs.
+ // Traverse all reached defs. This time dead defs cannot be ignored.
for (NodeId D = DefA.Addr->getReachedDef(), NextD; D != 0; D = NextD) {
auto DA = DFG.addr<DefNode*>(D);
NextD = DA.Addr->getSibling();
@@ -360,8 +375,10 @@ void Liveness::computePhiInfo() {
// are actually reached by the phi defs.
for (unsigned i = 0; i < DefQ.size(); ++i) {
NodeAddr<DefNode*> DA = DFG.addr<DefNode*>(DefQ[i]);
- // Visit all reached uses.
- NodeId UN = DA.Addr->getReachedUse();
+ // Visit all reached uses. Phi defs should not really have the "dead"
+ // flag set, but check it anyway for consistency.
+ bool IsDead = DA.Addr->getFlags() & NodeAttrs::Dead;
+ NodeId UN = !IsDead ? DA.Addr->getReachedUse() : 0;
while (UN != 0) {
NodeAddr<UseNode*> A = DFG.addr<UseNode*>(UN);
uint16_t F = A.Addr->getFlags();
@@ -409,6 +426,8 @@ void Liveness::computePhiInfo() {
NodeSet &Uses = UI->second;
for (auto I = Uses.begin(), E = Uses.end(); I != E; ) {
auto UA = DFG.addr<UseNode*>(*I);
+ // Undef flag is checked above.
+ assert((UA.Addr->getFlags() & NodeAttrs::Undef) == 0);
NodeList RDs = getAllReachingDefs(UI->first, UA);
if (any_of(RDs, InPhiDefs))
++I;
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