[ConstantFold] Support pointers in reinterpret load folding

Peculiarly, the necessary code to handle pointers (including the
check for non-integral address spaces) is already in place,
because we were already allowing vectors of pointers here, just
not plain pointers.

Author: nikic

llvm/lib/Analysis/ConstantFolding.cpp

@@ -558,7 +558,7 @@ Constant *FoldReinterpretLoadFromConst(Constant *C, Type *LoadTy,
     // that address spaces don't matter here since we're not going to result in
     // an actual new load.
     if (!LoadTy->isHalfTy() && !LoadTy->isFloatTy() && !LoadTy->isDoubleTy() &&
-        !LoadTy->isVectorTy())
+        !LoadTy->isPointerTy() && !LoadTy->isVectorTy())
       return nullptr;
 
     Type *MapTy = Type::getIntNTy(

llvm/test/Transforms/InstSimplify/ConstProp/loads.ll

@@ -340,9 +340,11 @@ define i32 @load_all_undef() {
 @g_i8_data = constant [16 x i8] c"\01\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00"
 
 define i64* @load_ptr_from_i8_data() {
-; CHECK-LABEL: @load_ptr_from_i8_data(
-; CHECK-NEXT:    [[V:%.*]] = load i64*, i64** bitcast ([16 x i8]* @g_i8_data to i64**), align 8
-; CHECK-NEXT:    ret i64* [[V]]
+; LE-LABEL: @load_ptr_from_i8_data(
+; LE-NEXT:    ret i64* inttoptr (i64 1 to i64*)
+;
+; BE-LABEL: @load_ptr_from_i8_data(
+; BE-NEXT:    ret i64* inttoptr (i64 72057594037927936 to i64*)
 ;
   %v = load i64*, i64** bitcast ([16 x i8]* @g_i8_data to i64**)
   ret i64* %v