[opaque pointer type]: Pass explicit pointee type when building a constant GEP.

Gets a bit tricky in the ValueMapper, of course - not sure if we should
just expose a list of explicit types for each Value so that the
ValueMapper can be neutral to these special cases (it's OK for things
like load, where the explicit type is the result type - but when that's
not the case, it means plumbing through another "special" type... )

llvm-svn: 245728

llvm/include/llvm/IR/Constants.h

@@ -1175,7 +1175,8 @@ public:
   /// gets constant-folded, the type changes, or the expression is otherwise
   /// canonicalized.  This parameter should almost always be \c false.
   Constant *getWithOperands(ArrayRef<Constant *> Ops, Type *Ty,
-                            bool OnlyIfReduced = false) const;
+                            bool OnlyIfReduced = false,
+                            Type *SrcTy = nullptr) const;
 
   /// getAsInstruction - Returns an Instruction which implements the same
   /// operation as this ConstantExpr. The instruction is not linked to any basic

llvm/lib/IR/Constants.cpp

@@ -1245,7 +1245,7 @@ ConstantExpr::getWithOperandReplaced(unsigned OpNo, Constant *Op) const {
 /// operands replaced with the specified values.  The specified array must
 /// have the same number of operands as our current one.
 Constant *ConstantExpr::getWithOperands(ArrayRef<Constant *> Ops, Type *Ty,
-                                        bool OnlyIfReduced) const {
+                                        bool OnlyIfReduced, Type *SrcTy) const {
   assert(Ops.size() == getNumOperands() && "Operand count mismatch!");
 
   // If no operands changed return self.
@@ -1283,10 +1283,13 @@ Constant *ConstantExpr::getWithOperands(ArrayRef<Constant *> Ops, Type *Ty,
   case Instruction::ShuffleVector:
     return ConstantExpr::getShuffleVector(Ops[0], Ops[1], Ops[2],
                                           OnlyIfReducedTy);
-  case Instruction::GetElementPtr:
-    return ConstantExpr::getGetElementPtr(nullptr, Ops[0], Ops.slice(1),
-                                          cast<GEPOperator>(this)->isInBounds(),
-                                          OnlyIfReducedTy);
+  case Instruction::GetElementPtr: {
+    auto *GEPO = cast<GEPOperator>(this);
+    assert(SrcTy || (Ops[0]->getType() == getOperand(0)->getType()));
+    return ConstantExpr::getGetElementPtr(
+        SrcTy ? SrcTy : GEPO->getSourceElementType(), Ops[0], Ops.slice(1),
+        GEPO->isInBounds(), OnlyIfReducedTy);
+  }
   case Instruction::ICmp:
   case Instruction::FCmp:
     return ConstantExpr::getCompare(getPredicate(), Ops[0], Ops[1],

llvm/lib/Transforms/Utils/ValueMapper.cpp

@@ -19,6 +19,7 @@
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Metadata.h"
+#include "llvm/IR/Operator.h"
 using namespace llvm;
 
 // Out of line method to get vtable etc for class.
@@ -127,9 +128,13 @@ Value *llvm::MapValue(const Value *V, ValueToValueMapTy &VM, RemapFlags Flags,
       Ops.push_back(MapValue(cast<Constant>(C->getOperand(OpNo)), VM,
                              Flags, TypeMapper, Materializer));
   }
-  
+  Type *NewSrcTy = nullptr;
+  if (TypeMapper)
+    if (auto *GEPO = dyn_cast<GEPOperator>(C))
+      NewSrcTy = TypeMapper->remapType(GEPO->getSourceElementType());
+
   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
-    return VM[V] = CE->getWithOperands(Ops, NewTy);
+    return VM[V] = CE->getWithOperands(Ops, NewTy, false, NewSrcTy);
   if (isa<ConstantArray>(C))
     return VM[V] = ConstantArray::get(cast<ArrayType>(NewTy), Ops);
   if (isa<ConstantStruct>(C))