[PATCH] D20846: [IR] Disallow loading and storing unsized types

[Sanjoy Das via llvm-commits]

sanjoy created this revision.
sanjoy added reviewers: majnemer, chandlerc.
sanjoy added a subscriber: llvm-commits.
Herald added a subscriber: mcrosier.

It isn't clear what is the operational meaning of loading or storing an
unsized types, since it cannot be lowered into something meaningful.
Since there does not seem to be any practical need for it either, make
such loads and stores illegal IR.

http://reviews.llvm.org/D20846

Files:
  docs/LangRef.rst
  lib/IR/Verifier.cpp
  test/Verifier/unsized-types.ll

Index: test/Verifier/unsized-types.ll
===================================================================
--- /dev/null
+++ test/Verifier/unsized-types.ll
@@ -0,0 +1,24 @@
+; RUN: not opt -verify < %s 2>&1 | FileCheck %s
+
+%X = type opaque
+
+define void @f_0(%X* %ptr) {
+  %t = load %X, %X* %ptr
+  ret void
+; CHECK: loading unsized types is not allowed
+; CHECK-NEXT:  %t = load %X, %X* %ptr
+}
+
+define void @f_1(%X %val, %X* %ptr) {
+  store %X %val, %X* %ptr
+  ret void
+; CHECK: storing unsized types is not allowed
+; CHECK-NEXT:  store %X %val, %X* %ptr
+}
+
+define void @f_2() {
+  %t = alloca %X
+  ret void
+; CHECK: Cannot allocate unsized type
+; CHECK-NEXT:  %t = alloca %X
+}
Index: lib/IR/Verifier.cpp
===================================================================
--- lib/IR/Verifier.cpp
+++ lib/IR/Verifier.cpp
@@ -2959,6 +2959,7 @@
   Type *ElTy = LI.getType();
   Assert(LI.getAlignment() <= Value::MaximumAlignment,
          "huge alignment values are unsupported", &LI);
+  Assert(ElTy->isSized(), "loading unsized types is not allowed", &LI);
   if (LI.isAtomic()) {
     Assert(LI.getOrdering() != AtomicOrdering::Release &&
                LI.getOrdering() != AtomicOrdering::AcquireRelease,
@@ -2987,6 +2988,7 @@
          "Stored value type does not match pointer operand type!", &SI, ElTy);
   Assert(SI.getAlignment() <= Value::MaximumAlignment,
          "huge alignment values are unsupported", &SI);
+  Assert(ElTy->isSized(), "storing unsized types is not allowed", &SI);
   if (SI.isAtomic()) {
     Assert(SI.getOrdering() != AtomicOrdering::Acquire &&
                SI.getOrdering() != AtomicOrdering::AcquireRelease,
Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -6977,12 +6977,12 @@
 Arguments:
 """"""""""
 
-The argument to the ``load`` instruction specifies the memory address
-from which to load. The type specified must be a :ref:`first
-class <t_firstclass>` type. If the ``load`` is marked as ``volatile``,
-then the optimizer is not allowed to modify the number or order of
-execution of this ``load`` with other :ref:`volatile
-operations <volatile>`.
+The argument to the ``load`` instruction specifies the memory address from which
+to load. The type specified must be a :ref:`first class <t_firstclass>` type of
+known size (i.e. not containing an :ref:`opaque structural type <t_opaque>`). If
+the ``load`` is marked as ``volatile``, then the optimizer is not allowed to
+modify the number or order of execution of this ``load`` with other
+:ref:`volatile operations <volatile>`.
 
 If the ``load`` is marked as ``atomic``, it takes an extra :ref:`ordering
 <ordering>` and optional ``singlethread`` argument. The ``release`` and
@@ -7100,13 +7100,14 @@
 Arguments:
 """"""""""
 
-There are two arguments to the ``store`` instruction: a value to store
-and an address at which to store it. The type of the ``<pointer>``
-operand must be a pointer to the :ref:`first class <t_firstclass>` type of
-the ``<value>`` operand. If the ``store`` is marked as ``volatile``,
-then the optimizer is not allowed to modify the number or order of
-execution of this ``store`` with other :ref:`volatile
-operations <volatile>`.
+There are two arguments to the ``store`` instruction: a value to store and an
+address at which to store it. The type of the ``<pointer>`` operand must be a
+pointer to the :ref:`first class <t_firstclass>` type of the ``<value>``
+operand. If the ``store`` is marked as ``volatile``, then the optimizer is not
+allowed to modify the number or order of execution of this ``store`` with other
+:ref:`volatile operations <volatile>`.  Only values of :ref:`first class
+<t_firstclass>` types of known size (i.e. not containing an :ref:`opaque
+structural type <t_opaque>`) can be stored.
 
 If the ``store`` is marked as ``atomic``, it takes an extra :ref:`ordering
 <ordering>` and optional ``singlethread`` argument. The ``acquire`` and


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