From 1076288e2254367d61be891eb16d854919c702e8 Mon Sep 17 00:00:00 2001
From: Reid Kleckner <rnk@google.com>
Date: Fri, 9 Sep 2016 17:29:36 +0000
Subject: [codeview] Don't assert if the array element type is incomplete

This can happen when the frontend knows the debug info will be emitted
somewhere else. Usually this happens for dynamic classes with out of
line constructors or key functions, but it can also happen when modules
are enabled.

llvm-svn: 281060
---
 llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp | 41 +++++++++++++++++----------
 1 file changed, 26 insertions(+), 15 deletions(-)

(limited to 'llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp')

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index 51a5d06..5216577 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -994,20 +994,25 @@ TypeIndex CodeViewDebug::lowerTypeArray(const DICompositeType *Ty) {
 
   uint64_t ElementSize = getBaseTypeSize(ElementTypeRef) / 8;
 
-  bool UndefinedSubrange = false;
 
-  // FIXME:
-  // There is a bug in the front-end where an array of a structure, which was
-  // declared as incomplete structure first, ends up not getting a size assigned
-  // to it. (PR28303)
+  // We want to assert that the element type multiplied by the array lengths
+  // match the size of the overall array. However, if we don't have complete
+  // type information for the base type, we can't make this assertion. This
+  // happens if limited debug info is enabled in this case:
+  //   struct VTableOptzn { VTableOptzn(); virtual ~VTableOptzn(); };
+  //   VTableOptzn array[3];
+  // The DICompositeType of VTableOptzn will have size zero, and the array will
+  // have size 3 * sizeof(void*), and we should avoid asserting.
+  //
+  // There is a related bug in the front-end where an array of a structure,
+  // which was declared as incomplete structure first, ends up not getting a
+  // size assigned to it. (PR28303)
   // Example:
   //   struct A(*p)[3];
   //   struct A { int f; } a[3];
-  //
-  // This needs to be fixed in the front-end, but in the meantime we don't want
-  // to trigger an assertion because of this.
-  if (Ty->getSizeInBits() == 0) {
-    UndefinedSubrange = true;
+  bool PartiallyIncomplete = false;
+  if (Ty->getSizeInBits() == 0 || ElementSize == 0) {
+    PartiallyIncomplete = true;
   }
 
   // Add subranges to array type.
@@ -1026,18 +1031,24 @@ TypeIndex CodeViewDebug::lowerTypeArray(const DICompositeType *Ty) {
     // FIXME: Make front-end support VLA subrange and emit LF_DIMVARLU.
     if (Count == -1) {
       Count = 1;
-      UndefinedSubrange = true;
+      PartiallyIncomplete = true;
     }
 
-    StringRef Name = (i == 0) ? Ty->getName() : "";
     // Update the element size and element type index for subsequent subranges.
     ElementSize *= Count;
+
+    // If this is the outermost array, use the size from the array. It will be
+    // more accurate if PartiallyIncomplete is true.
+    uint64_t ArraySize =
+        (i == 0 && ElementSize == 0) ? Ty->getSizeInBits() / 8 : ElementSize;
+
+    StringRef Name = (i == 0) ? Ty->getName() : "";
     ElementTypeIndex = TypeTable.writeKnownType(
-        ArrayRecord(ElementTypeIndex, IndexType, ElementSize, Name));
+        ArrayRecord(ElementTypeIndex, IndexType, ArraySize, Name));
   }
 
-  (void)UndefinedSubrange;
-  assert(UndefinedSubrange || ElementSize == (Ty->getSizeInBits() / 8));
+  (void)PartiallyIncomplete;
+  assert(PartiallyIncomplete || ElementSize == (Ty->getSizeInBits() / 8));
 
   return ElementTypeIndex;
 }
-- 
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