[llvm] r239616 - Don't create instructions from ConstantExpr's in CFLAliasAnalysis.

[Pete Cooper]

Author: pete
Date: Fri Jun 12 11:13:54 2015
New Revision: 239616

URL: http://llvm.org/viewvc/llvm-project?rev=239616&view=rev
Log:
Don't create instructions from ConstantExpr's in CFLAliasAnalysis.

The CFLAA code currently calls ConstantExpr::getAsInstruction which creates an instruction from a constant expr.

We then pass that instruction to the InstVisitor to analyze it.

Its not necessary to create these instructions as we can just cast from Constant to Operator in the visitor.  This is how other InstVisitor’s such as SelectionDAGBuilder handle ConstantExpr.

Modified:
    llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp

Modified: llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp?rev=239616&r1=239615&r2=239616&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp (original)
+++ llvm/trunk/lib/Analysis/CFLAliasAnalysis.cpp Fri Jun 12 11:13:54 2015
@@ -539,6 +539,19 @@ public:
     Output.push_back(Edge(&Inst, From1, EdgeType::Assign, AttrNone));
     Output.push_back(Edge(&Inst, From2, EdgeType::Assign, AttrNone));
   }
+
+  void visitConstantExpr(ConstantExpr *CE) {
+    switch (CE->getOpcode()) {
+    default:
+      llvm_unreachable("Unknown instruction type encountered!");
+// Build the switch statement using the Instruction.def file.
+#define HANDLE_INST(NUM, OPCODE, CLASS)                                        \
+  case Instruction::OPCODE:                                                    \
+    visit##OPCODE(*(CLASS *)CE);                                               \
+    break;
+#include "llvm/IR/Instruction.def"
+    }
+  }
 };
 
 // For a given instruction, we need to know which Value* to get the
@@ -741,6 +754,10 @@ static EdgeType flipWeight(EdgeType);
 static void argsToEdges(CFLAliasAnalysis &, Instruction *,
                         SmallVectorImpl<Edge> &);
 
+// Gets edges of the given ConstantExpr*, writing them to the SmallVector*.
+static void argsToEdges(CFLAliasAnalysis &, ConstantExpr *,
+                        SmallVectorImpl<Edge> &);
+
 // Gets the "Level" that one should travel in StratifiedSets
 // given an EdgeType.
 static Level directionOfEdgeType(EdgeType);
@@ -807,6 +824,13 @@ static bool hasUsefulEdges(Instruction *
   return !isa<CmpInst>(Inst) && !isa<FenceInst>(Inst) && !IsNonInvokeTerminator;
 }
 
+static bool hasUsefulEdges(ConstantExpr *CE) {
+  // ConstantExpr doens't have terminators, invokes, or fences, so only needs
+  // to check for compares.
+  return CE->getOpcode() != Instruction::ICmp &&
+         CE->getOpcode() != Instruction::FCmp;
+}
+
 static Optional<StratifiedAttr> valueToAttrIndex(Value *Val) {
   if (isa<GlobalValue>(Val))
     return AttrGlobalIndex;
@@ -846,6 +870,13 @@ static void argsToEdges(CFLAliasAnalysis
   v.visit(Inst);
 }
 
+static void argsToEdges(CFLAliasAnalysis &Analysis, ConstantExpr *CE,
+                        SmallVectorImpl<Edge> &Output) {
+  assert(hasUsefulEdges(CE) && "Expected constant expr to have 'useful' edges");
+  GetEdgesVisitor v(Analysis, Output);
+  v.visitConstantExpr(CE);
+}
+
 static Level directionOfEdgeType(EdgeType Weight) {
   switch (Weight) {
   case EdgeType::Reference:
@@ -865,25 +896,23 @@ static void constexprToEdges(CFLAliasAna
   Worklist.push_back(&CExprToCollapse);
 
   SmallVector<Edge, 8> ConstexprEdges;
+  SmallPtrSet<ConstantExpr *, 4> Visited;
   while (!Worklist.empty()) {
     auto *CExpr = Worklist.pop_back_val();
-    std::unique_ptr<Instruction> Inst(CExpr->getAsInstruction());
 
-    if (!hasUsefulEdges(Inst.get()))
+    if (!hasUsefulEdges(CExpr))
       continue;
 
     ConstexprEdges.clear();
-    argsToEdges(Analysis, Inst.get(), ConstexprEdges);
+    argsToEdges(Analysis, CExpr, ConstexprEdges);
     for (auto &Edge : ConstexprEdges) {
-      if (Edge.From == Inst.get())
-        Edge.From = CExpr;
-      else if (auto *Nested = dyn_cast<ConstantExpr>(Edge.From))
-        Worklist.push_back(Nested);
-
-      if (Edge.To == Inst.get())
-        Edge.To = CExpr;
-      else if (auto *Nested = dyn_cast<ConstantExpr>(Edge.To))
-        Worklist.push_back(Nested);
+      if (auto *Nested = dyn_cast<ConstantExpr>(Edge.From))
+        if (Visited.insert(Nested).second)
+          Worklist.push_back(Nested);
+
+      if (auto *Nested = dyn_cast<ConstantExpr>(Edge.To))
+        if (Visited.insert(Nested).second)
+          Worklist.push_back(Nested);
     }
 
     Results.append(ConstexprEdges.begin(), ConstexprEdges.end());