r206681 - Thread Safety Analysis: Convert to minimal SSA.
DeLesley Hutchins
delesley at google.com
Fri Apr 18 20:54:41 PDT 2014
Author: delesley
Date: Fri Apr 18 22:54:41 2014
New Revision: 206681
URL: http://llvm.org/viewvc/llvm-project?rev=206681&view=rev
Log:
Thread Safety Analysis: Convert to minimal SSA.
Modified:
cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyCommon.h
cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTIL.h
cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTraverse.h
cfe/trunk/lib/Analysis/ThreadSafetyCommon.cpp
Modified: cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyCommon.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyCommon.h?rev=206681&r1=206680&r2=206681&view=diff
==============================================================================
--- cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyCommon.h (original)
+++ cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyCommon.h Fri Apr 18 22:54:41 2014
@@ -365,6 +365,7 @@ private:
LVarDefinitionMap CurrentLVarMap;
std::vector<til::Variable*> CurrentArguments;
std::vector<til::Variable*> CurrentInstructions;
+ std::vector<til::Variable*> IncompleteArgs;
til::BasicBlock *CurrentBB;
BlockInfo *CurrentBlockInfo;
};
Modified: cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTIL.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTIL.h?rev=206681&r1=206680&r2=206681&view=diff
==============================================================================
--- cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTIL.h (original)
+++ cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTIL.h Fri Apr 18 22:54:41 2014
@@ -162,7 +162,7 @@ private:
// Contains various helper functions for SExprs.
namespace ThreadSafetyTIL {
- inline bool isTrivial(SExpr *E) {
+ inline bool isTrivial(const SExpr *E) {
unsigned Op = E->opcode();
return Op == COP_Variable || Op == COP_Literal || Op == COP_LiteralPtr;
}
@@ -209,6 +209,7 @@ public:
// Returns the definition (for let vars) or type (for parameter & self vars)
SExpr *definition() { return Definition.get(); }
+ const SExpr *definition() const { return Definition.get(); }
void attachVar() const { ++NumUses; }
void detachVar() const { assert(NumUses > 0); --NumUses; }
@@ -1107,6 +1108,15 @@ public:
// TODO: change to SExprRef
typedef SimpleArray<SExpr *> ValArray;
+ // In minimal SSA form, all Phi nodes are MultiVal.
+ // During conversion to SSA, incomplete Phi nodes may be introduced, which
+ // are later determined to be SingleVal.
+ enum Status {
+ PH_MultiVal = 0, // Phi node has multiple distinct values. (Normal)
+ PH_SingleVal, // Phi node has one distinct value, and can be eliminated
+ PH_Incomplete // Phi node is incomplete
+ };
+
static bool classof(const SExpr *E) { return E->opcode() == COP_Phi; }
Phi(MemRegionRef A, unsigned Nvals) : SExpr(COP_Phi), Values(A, Nvals) {}
@@ -1116,14 +1126,8 @@ public:
const ValArray &values() const { return Values; }
ValArray &values() { return Values; }
- // Incomplete phi nodes are constructed during SSA conversion, and
- // may not be necessary.
- bool incomplete() const { return Flags == 1; }
-
- void setIncomplete(bool b) {
- if (b) Flags = 1;
- else Flags = 0;
- }
+ Status status() const { return static_cast<Status>(Flags); }
+ void setStatus(Status s) { Flags = s; }
template <class V> typename V::R_SExpr traverse(V &Visitor) {
typename V::template Container<typename V::R_SExpr> Nvs(Visitor,
@@ -1222,6 +1226,12 @@ private:
};
+SExpr *getCanonicalVal(SExpr *E);
+void simplifyIncompleteArg(Variable *V, til::Phi *Ph);
+
+
+
+
} // end namespace til
} // end namespace threadSafety
} // end namespace clang
Modified: cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTraverse.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTraverse.h?rev=206681&r1=206680&r2=206681&view=diff
==============================================================================
--- cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTraverse.h (original)
+++ cfe/trunk/include/clang/Analysis/Analyses/ThreadSafetyTraverse.h Fri Apr 18 22:54:41 2014
@@ -505,16 +505,42 @@ protected:
}
void printLiteral(Literal *E, StreamType &SS) {
- // TODO: actually pretty print the literal.
- SS << "#lit";
+ const clang::Expr *CE = E->clangExpr();
+ switch (CE->getStmtClass()) {
+ case Stmt::IntegerLiteralClass:
+ SS << cast<IntegerLiteral>(CE)->getValue().toString(10, true);
+ return;
+ case Stmt::StringLiteralClass:
+ SS << "\"" << cast<StringLiteral>(CE)->getString() << "\"";
+ return;
+ case Stmt::CharacterLiteralClass:
+ case Stmt::CXXNullPtrLiteralExprClass:
+ case Stmt::GNUNullExprClass:
+ case Stmt::CXXBoolLiteralExprClass:
+ case Stmt::FloatingLiteralClass:
+ case Stmt::ImaginaryLiteralClass:
+ case Stmt::ObjCStringLiteralClass:
+ default:
+ SS << "#lit";
+ return;
+ }
}
void printLiteralPtr(LiteralPtr *E, StreamType &SS) {
SS << E->clangDecl()->getNameAsString();
}
- void printVariable(Variable *E, StreamType &SS) {
+ void printVariable(Variable *E, StreamType &SS, bool IsVarDecl = false) {
SS << E->name() << E->getBlockID() << "_" << E->getID();
+ if (IsVarDecl)
+ return;
+
+ SExpr *V = getCanonicalVal(E);
+ if (V != E) {
+ SS << "{";
+ printSExpr(V, SS, Prec_MAX);
+ SS << "}";
+ }
}
void printFunction(Function *E, StreamType &SS, unsigned sugared = 0) {
@@ -528,7 +554,7 @@ protected:
SS << ", "; // Curried functions
break;
}
- self()->printVariable(E->variableDecl(), SS);
+ self()->printVariable(E->variableDecl(), SS, true);
SS << ": ";
self()->printSExpr(E->variableDecl()->definition(), SS, Prec_MAX);
@@ -541,7 +567,7 @@ protected:
void printSFunction(SFunction *E, StreamType &SS) {
SS << "@";
- self()->printVariable(E->variableDecl(), SS);
+ self()->printVariable(E->variableDecl(), SS, true);
SS << " ";
self()->printSExpr(E->body(), SS, Prec_Decl);
}
@@ -632,7 +658,7 @@ protected:
newline(SS);
for (auto A : BBI->arguments()) {
SS << "let ";
- self()->printVariable(A, SS);
+ self()->printVariable(A, SS, true);
SS << " = ";
self()->printSExpr(A->definition(), SS, Prec_MAX);
SS << ";";
@@ -641,7 +667,7 @@ protected:
for (auto I : BBI->instructions()) {
if (I->definition()->opcode() != COP_Store) {
SS << "let ";
- self()->printVariable(I, SS);
+ self()->printVariable(I, SS, true);
SS << " = ";
}
self()->printSExpr(I->definition(), SS, Prec_MAX);
@@ -663,11 +689,16 @@ protected:
void printPhi(Phi *E, StreamType &SS) {
SS << "phi(";
unsigned i = 0;
- for (auto V : E->values()) {
- if (i > 0)
- SS << ", ";
- self()->printSExpr(V, SS, Prec_MAX);
- ++i;
+ if (E->status() == Phi::PH_SingleVal) {
+ self()->printSExpr(E->values()[0], SS, Prec_MAX);
+ }
+ else {
+ for (auto V : E->values()) {
+ if (i > 0)
+ SS << ", ";
+ self()->printSExpr(V, SS, Prec_MAX);
+ ++i;
+ }
}
SS << ")";
}
Modified: cfe/trunk/lib/Analysis/ThreadSafetyCommon.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Analysis/ThreadSafetyCommon.cpp?rev=206681&r1=206680&r2=206681&view=diff
==============================================================================
--- cfe/trunk/lib/Analysis/ThreadSafetyCommon.cpp (original)
+++ cfe/trunk/lib/Analysis/ThreadSafetyCommon.cpp Fri Apr 18 22:54:41 2014
@@ -36,6 +36,65 @@
namespace clang {
namespace threadSafety {
+namespace til {
+
+// If E is a variable, then trace back through any aliases or redundant
+// Phi nodes to find the canonical definition.
+SExpr *getCanonicalVal(SExpr *E) {
+ while (auto *V = dyn_cast<Variable>(E)) {
+ SExpr *D;
+ do {
+ if (V->kind() != Variable::VK_Let)
+ return V;
+ D = V->definition();
+ if (auto *V2 = dyn_cast<Variable>(D)) {
+ V = V2;
+ continue;
+ }
+ } while(false);
+
+ if (ThreadSafetyTIL::isTrivial(D))
+ return D;
+
+ if (Phi *Ph = dyn_cast<Phi>(D)) {
+ if (Ph->status() == Phi::PH_Incomplete)
+ simplifyIncompleteArg(V, Ph);
+
+ if (Ph->status() == Phi::PH_SingleVal) {
+ E = Ph->values()[0];
+ continue;
+ }
+ }
+ return V;
+ }
+ return E;
+}
+
+
+// Trace the arguments of an incomplete Phi node to see if they have the same
+// canonical definition. If so, mark the Phi node as redundant.
+// getCanonicalVal() will recursively call simplifyIncompletePhi().
+void simplifyIncompleteArg(Variable *V, til::Phi *Ph) {
+ assert(!Ph && Ph->status() == Phi::PH_Incomplete);
+
+ // eliminate infinite recursion -- assume that this node is not redundant.
+ Ph->setStatus(Phi::PH_MultiVal);
+
+ SExpr *E0 = getCanonicalVal(Ph->values()[0]);
+ for (unsigned i=1, n=Ph->values().size(); i<n; ++i) {
+ SExpr *Ei = getCanonicalVal(Ph->values()[i]);
+ if (Ei == V)
+ continue; // Recursive reference to itself. Don't count.
+ if (Ei != E0) {
+ return; // Status is already set to MultiVal.
+ }
+ }
+ Ph->setStatus(Phi::PH_SingleVal);
+}
+
+} // end namespace til
+
+
typedef SExprBuilder::CallingContext CallingContext;
@@ -416,19 +475,6 @@ til::SExpr *SExprBuilder::updateVarDecl(
}
-// Return true if the given expression represents a possibly unnecessary
-// variable: i.e. a variable that references a Phi node that may be removed.
-inline bool isIncompleteVar(til::SExpr *E) {
- if (!E)
- return true; // Null values are used on unknown backedges.
- if (til::Variable *V = dyn_cast<til::Variable>(E)) {
- if (til::Phi *Ph = dyn_cast<til::Phi>(V->definition()))
- return Ph->incomplete();
- }
- return false;
-}
-
-
// Make a Phi node in the current block for the i^th variable in CurrentVarMap.
// If E != null, sets Phi[CurrentBlockInfo->ArgIndex] = E.
// If E == null, this is a backedge and will be set later.
@@ -444,8 +490,6 @@ void SExprBuilder::makePhiNodeVar(unsign
assert(Ph && "Expecting Phi node.");
if (E)
Ph->values()[ArgIndex] = E;
- if (!Ph->incomplete() && isIncompleteVar(E))
- Ph->setIncomplete(true);
return;
}
@@ -457,12 +501,16 @@ void SExprBuilder::makePhiNodeVar(unsign
Ph->values()[PIdx] = CurrentLVarMap[i].second;
if (E)
Ph->values()[ArgIndex] = E;
- if (isIncompleteVar(E))
- Ph->setIncomplete(true);
+ if (!E) {
+ // This is a non-minimal SSA node, which may be removed later.
+ Ph->setStatus(til::Phi::PH_Incomplete);
+ }
// Add Phi node to current block, and update CurrentLVarMap[i]
auto *Var = new (Arena) til::Variable(Ph, CurrentLVarMap[i].first);
CurrentArguments.push_back(Var);
+ if (Ph->status() == til::Phi::PH_Incomplete)
+ IncompleteArgs.push_back(Var);
CurrentLVarMap.makeWritable();
CurrentLVarMap.elem(i).second = Var;
@@ -680,8 +728,15 @@ void SExprBuilder::exitCFGBlock(const CF
void SExprBuilder::exitCFG(const CFGBlock *Last) {
+ for (auto *V : IncompleteArgs) {
+ til::Phi *Ph = dyn_cast<til::Phi>(V->definition());
+ if (Ph && Ph->status() == til::Phi::PH_Incomplete)
+ simplifyIncompleteArg(V, Ph);
+ }
+
CurrentArguments.clear();
CurrentInstructions.clear();
+ IncompleteArgs.clear();
}
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