Remove the API for creating ConstantExprs with the nsw, nuw, inbounds,

and exact flags. Because ConstantExprs are uniqued, creating an
expression with this flag causes all expressions with the same operands
to have the same flag, which may not be safe. Add, sub, mul, and sdiv
ConstantExprs are usually folded anyway, so the main interesting flag
here is inbounds, and the constant folder already knows how to set the
inbounds flag automatically in most cases, so there isn't an urgent need
for the API support.

This can be reconsidered in the future, but for now just removing these
API bits eliminates a source of potential trouble with little downside.

llvm-svn: 80959

1 files changed, 12 insertions, 6 deletions

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 109eaad4584..9bc00938816 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -203,15 +203,21 @@ static Constant *SymbolicallyEvaluateGEP(Constant* const* Ops, unsigned NumOps,
   if (Offset != 0)
     return 0;
 
+  // Create the GEP constant expr.
+  Constant *C = ConstantExpr::getGetElementPtr(Ptr,
+                                               &NewIdxs[0], NewIdxs.size());
+  assert(cast<PointerType>(C->getType())->getElementType() == Ty &&
+         "Computed GetElementPtr has unexpected type!");
+
   // If the base is the start of a GlobalVariable and all the array indices
   // remain in their static bounds, the GEP is inbounds. We can check that
   // all indices are in bounds by just checking the first index only
-  // because we've just normalized all the indices.
-  Constant *C = isa<GlobalVariable>(Ptr) && NewIdxs[0]->isNullValue() ?
-    ConstantExpr::getInBoundsGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size()) :
-    ConstantExpr::getGetElementPtr(Ptr, &NewIdxs[0], NewIdxs.size());
-  assert(cast<PointerType>(C->getType())->getElementType() == Ty &&
-         "Computed GetElementPtr has unexpected type!");
+  // because we've just normalized all the indices. We can mutate the
+  // Constant in place because we've proven that the indices are in bounds,
+  // so they'll always be in bounds.
+  if (isa<GlobalVariable>(Ptr) && NewIdxs[0]->isNullValue())
+    if (GEPOperator *GEP = dyn_cast<GEPOperator>(C))
+      GEP->setIsInBounds(true);
 
   // If we ended up indexing a member with a type that doesn't match
   // the type of what the original indices indexed, add a cast.