switch SCEV to use the new ConstantFoldLoadThroughGEPIndices function

instead of its own hard coded thing, allowing it to handle
ConstantDataSequential and fixing some obscure bugs (e.g. it would
previously crash on a CAZ of vector type).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148788 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index caf360650d0625d6ada8a9003a609c8ed0b4cdc7..0c0ceeb951624cb6d34ec14bc8056952137b664e 100644 (file)
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -4580,39 +4580,6 @@ EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
   return cast<SCEVConstant>(Val)->getValue();
 }
 
-/// GetAddressedElementFromGlobal - Given a global variable with an initializer
-/// and a GEP expression (missing the pointer index) indexing into it, return
-/// the addressed element of the initializer or null if the index expression is
-/// invalid.
-static Constant *
-GetAddressedElementFromGlobal(GlobalVariable *GV,
-                              const std::vector<ConstantInt*> &Indices) {
-  Constant *Init = GV->getInitializer();
-  for (unsigned i = 0, e = Indices.size(); i != e; ++i) {
-    uint64_t Idx = Indices[i]->getZExtValue();
-    if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) {
-      assert(Idx < CS->getNumOperands() && "Bad struct index!");
-      Init = cast<Constant>(CS->getOperand(Idx));
-    } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) {
-      if (Idx >= CA->getNumOperands()) return 0;  // Bogus program
-      Init = cast<Constant>(CA->getOperand(Idx));
-    } else if (isa<ConstantAggregateZero>(Init)) {
-      if (StructType *STy = dyn_cast<StructType>(Init->getType())) {
-        assert(Idx < STy->getNumElements() && "Bad struct index!");
-        Init = Constant::getNullValue(STy->getElementType(Idx));
-      } else if (ArrayType *ATy = dyn_cast<ArrayType>(Init->getType())) {
-        if (Idx >= ATy->getNumElements()) return 0;  // Bogus program
-        Init = Constant::getNullValue(ATy->getElementType());
-      } else {
-        llvm_unreachable("Unknown constant aggregate type!");
-      }
-    } else {
-      return 0; // Unknown initializer type
-    }
-  }
-  return Init;
-}
-
 /// ComputeLoadConstantCompareExitLimit - Given an exit condition of
 /// 'icmp op load X, cst', try to see if we can compute the backedge
 /// execution count.
@@ -4640,7 +4607,7 @@ ScalarEvolution::ComputeLoadConstantCompareExitLimit(
 
   // Okay, we allow one non-constant index into the GEP instruction.
   Value *VarIdx = 0;
-  std::vector<ConstantInt*> Indexes;
+  std::vector<Constant*> Indexes;
   unsigned VarIdxNum = 0;
   for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
     if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
@@ -4674,7 +4641,8 @@ ScalarEvolution::ComputeLoadConstantCompareExitLimit(
     // Form the GEP offset.
     Indexes[VarIdxNum] = Val;
 
-    Constant *Result = GetAddressedElementFromGlobal(GV, Indexes);
+    Constant *Result = ConstantFoldLoadThroughGEPIndices(GV->getInitializer(),
+                                                         Indexes);
     if (Result == 0) break;  // Cannot compute!
 
     // Evaluate the condition for this iteration.