Analysis: only query size of sized objects.

Recently we started looking into sret parameters, though the issue could crop
up elsewhere. If the pointee type is opaque, we should not try to compute its
size because that leads to an assertion failure.

llvm/lib/Analysis/MemoryBuiltins.cpp

@@ -678,7 +678,7 @@ SizeOffsetType ObjectSizeOffsetVisitor::visitAllocaInst(AllocaInst &I) {
 SizeOffsetType ObjectSizeOffsetVisitor::visitArgument(Argument &A) {
   Type *MemoryTy = A.getPointeeInMemoryValueType();
   // No interprocedural analysis is done at the moment.
-  if (!MemoryTy) {
+  if (!MemoryTy|| !MemoryTy->isSized()) {
     ++ObjectVisitorArgument;
     return unknown();
   }

llvm/test/Transforms/InstCombine/object-size-opaque.ll

@@ -0,0 +1,12 @@
+; RUN: opt -instcombine -S %s | FileCheck %s
+%opaque = type opaque
+
+; CHECK: call i64 @llvm.objectsize.i64
+define void @foo(%opaque* sret %in, i64* %sizeptr) {
+  %ptr = bitcast %opaque* %in to i8*
+  %size = call i64 @llvm.objectsize.i64(i8* %ptr, i1 0, i1 0, i1 0)
+  store i64 %size, i64* %sizeptr
+  ret void
+}
+
+declare i64 @llvm.objectsize.i64(i8*, i1, i1, i1)