Fix fairly severe bug in my last checking where we treated all unfoldable

constants as being "true" when evaluating branches.  This was introduced
because we now create constantexprs for the constants instead of failing the
fold.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10778 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 3 deletions

diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index 3c92afe8cf..a570ba8b13 100644
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -362,8 +362,10 @@ void SCCP::getFeasibleSuccessors(TerminatorInst &TI, std::vector<bool> &Succs) {
       Succs[0] = true;
     } else {
       InstVal &BCValue = getValueState(BI->getCondition());
-      if (BCValue.isOverdefined()) {
-        // Overdefined condition variables mean the branch could go either way.
+      if (BCValue.isOverdefined() ||
+          (BCValue.isConstant() && !isa<ConstantBool>(BCValue.getConstant()))) {
+        // Overdefined condition variables, and branches on unfoldable constant
+        // conditions, mean the branch could go either way.
         Succs[0] = Succs[1] = true;
       } else if (BCValue.isConstant()) {
         // Constant condition variables mean the branch can only go a single way
@@ -375,7 +377,8 @@ void SCCP::getFeasibleSuccessors(TerminatorInst &TI, std::vector<bool> &Succs) {
     Succs[0] = Succs[1] = true;
   } else if (SwitchInst *SI = dyn_cast<SwitchInst>(&TI)) {
     InstVal &SCValue = getValueState(SI->getCondition());
-    if (SCValue.isOverdefined()) {  // Overdefined condition?
+    if (SCValue.isOverdefined() ||   // Overdefined condition?
+        (SCValue.isConstant() && !isa<ConstantInt>(SCValue.getConstant()))) {
       // All destinations are executable!
       Succs.assign(TI.getNumSuccessors(), true);
     } else if (SCValue.isConstant()) {
@@ -419,6 +422,9 @@ bool SCCP::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
         // Overdefined condition variables mean the branch could go either way.
         return true;
       } else if (BCValue.isConstant()) {
+        // Not branching on an evaluatable constant?
+        if (!isa<ConstantBool>(BCValue.getConstant())) return true;
+
         // Constant condition variables mean the branch can only go a single way
         return BI->getSuccessor(BCValue.getConstant() == 
                                        ConstantBool::False) == To;
@@ -435,6 +441,9 @@ bool SCCP::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
       return true;
     } else if (SCValue.isConstant()) {
       Constant *CPV = SCValue.getConstant();
+      if (!isa<ConstantInt>(CPV))
+        return true;  // not a foldable constant?
+
       // Make sure to skip the "default value" which isn't a value
       for (unsigned i = 1, E = SI->getNumSuccessors(); i != E; ++i)
         if (SI->getSuccessorValue(i) == CPV) // Found the taken branch...