[IndVars] Turn isValidRewrite into an assertion

[android-x86/external-llvm.git] / lib / Transforms / Scalar / IndVarSimplify.cpp

diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp
index 0683636..e7578c5 100644 (file)
--- a/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -136,7 +136,9 @@ class IndVarSimplify {
   SmallVector<WeakTrackingVH, 16> DeadInsts;
   bool Changed = false;
 
+#ifndef NDEBUG
   bool isValidRewrite(Value *FromVal, Value *ToVal);
+#endif
 
   void handleFloatingPointIV(Loop *L, PHINode *PH);
   void rewriteNonIntegerIVs(Loop *L);
@@ -163,18 +165,17 @@ public:
 
 } // end anonymous namespace
 
+#ifndef NDEBUG
 /// Return true if the SCEV expansion generated by the rewriter can replace the
 /// original value. SCEV guarantees that it produces the same value, but the way
-/// it is produced may be illegal IR.  Ideally, this function will only be
-/// called for verification.
+/// it is produced may be illegal IR.
 bool IndVarSimplify::isValidRewrite(Value *FromVal, Value *ToVal) {
   // If an SCEV expression subsumed multiple pointers, its expansion could
   // reassociate the GEP changing the base pointer. This is illegal because the
   // final address produced by a GEP chain must be inbounds relative to its
   // underlying object. Otherwise basic alias analysis, among other things,
-  // could fail in a dangerous way. Ultimately, SCEV will be improved to avoid
-  // producing an expression involving multiple pointers. Until then, we must
-  // bail out here.
+  // could fail in a dangerous way. Specifically, we want to make sure that SCEV
+  // does not convert gep Base, (&p[n] - &p[0]) into gep &p[n], Base - &p[0].
   //
   // Retrieve the pointer operand of the GEP. Don't use GetUnderlyingObject
   // because it understands lcssa phis while SCEV does not.
@@ -214,6 +215,7 @@ bool IndVarSimplify::isValidRewrite(Value *FromVal, Value *ToVal) {
   }
   return true;
 }
+#endif
 
 /// Determine the insertion point for this user. By default, insert immediately
 /// before the user. SCEVExpander or LICM will hoist loop invariants out of the
@@ -640,10 +642,7 @@ void IndVarSimplify::rewriteLoopExitValues(Loop *L, SCEVExpander &Rewriter) {
                           << '\n'
                           << "  LoopVal = " << *Inst << "\n");
 
-        if (!isValidRewrite(Inst, ExitVal)) {
-          DeadInsts.push_back(ExitVal);
-          continue;
-        }
+        assert(isValidRewrite(Inst, ExitVal) && "Must be!");
 
 #ifndef NDEBUG
         // If we reuse an instruction from a loop which is neither L nor one of