Revert "[ConstantFold] Handle vectors in ConstantFoldLoadThroughBitcast()"

That commit caused chromium build to crash: https://bugs.chromium.org/p/chromium/issues/detail?id=1188885

This reverts commit edf7004.

Author: ZequanWu

llvm/lib/Analysis/ConstantFolding.cpp

@@ -387,6 +387,11 @@ Constant *llvm::ConstantFoldLoadThroughBitcast(Constant *C, Type *DestTy,
         return ConstantExpr::getCast(Cast, C, DestTy);
     }
 
+    // If this isn't an aggregate type, there is nothing we can do to drill down
+    // and find a bitcastable constant.
+    if (!SrcTy->isAggregateType())
+      return nullptr;
+
     // We're simulating a load through a pointer that was bitcast to point to
     // a different type, so we can try to walk down through the initial
     // elements of an aggregate to see if some part of the aggregate is

llvm/test/Transforms/GVN/non-integral-pointers-inseltpoison.ll

@@ -213,12 +213,14 @@ entry:
   ret i64 addrspace(4)* %ref
 }
 
+; TODO: missed optimization
 define i8 addrspace(4)* @forward_memcopy(i8 addrspace(4)* addrspace(4)* %loc) {
 ; CHECK-LABEL: @forward_memcopy(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[LOC_BC:%.*]] = bitcast i8 addrspace(4)* addrspace(4)* [[LOC:%.*]] to i8 addrspace(4)*
 ; CHECK-NEXT:    call void @llvm.memcpy.p4i8.p0i8.i64(i8 addrspace(4)* align 4 [[LOC_BC]], i8* bitcast (<4 x i64 addrspace(4)*>* @NonZeroConstant2 to i8*), i64 8, i1 false)
-; CHECK-NEXT:    ret i8 addrspace(4)* bitcast (i64 addrspace(4)* getelementptr (i64, i64 addrspace(4)* null, i32 3) to i8 addrspace(4)*)
+; CHECK-NEXT:    [[REF:%.*]] = load i8 addrspace(4)*, i8 addrspace(4)* addrspace(4)* [[LOC]], align 8
+; CHECK-NEXT:    ret i8 addrspace(4)* [[REF]]
 ;
 entry:
   %loc.bc = bitcast i8 addrspace(4)* addrspace(4)* %loc to i8 addrspace(4)*

llvm/test/Transforms/GVN/non-integral-pointers.ll

@@ -213,12 +213,14 @@ entry:
   ret i64 addrspace(4)* %ref
 }
 
+; TODO: missed optimization
 define i8 addrspace(4)* @forward_memcopy(i8 addrspace(4)* addrspace(4)* %loc) {
 ; CHECK-LABEL: @forward_memcopy(
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[LOC_BC:%.*]] = bitcast i8 addrspace(4)* addrspace(4)* [[LOC:%.*]] to i8 addrspace(4)*
 ; CHECK-NEXT:    call void @llvm.memcpy.p4i8.p0i8.i64(i8 addrspace(4)* align 4 [[LOC_BC]], i8* bitcast (<4 x i64 addrspace(4)*>* @NonZeroConstant2 to i8*), i64 8, i1 false)
-; CHECK-NEXT:    ret i8 addrspace(4)* bitcast (i64 addrspace(4)* getelementptr (i64, i64 addrspace(4)* null, i32 3) to i8 addrspace(4)*)
+; CHECK-NEXT:    [[REF:%.*]] = load i8 addrspace(4)*, i8 addrspace(4)* addrspace(4)* [[LOC]], align 8
+; CHECK-NEXT:    ret i8 addrspace(4)* [[REF]]
 ;
 entry:
   %loc.bc = bitcast i8 addrspace(4)* addrspace(4)* %loc to i8 addrspace(4)*