[LLVMbugs] [Bug 4963] New: constant folding insertvalue loses packedness of struct

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=4963

           Summary: constant folding insertvalue loses packedness of struct
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Keywords: miscompilation
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: tomas.l.olsen at gmail.com
                CC: llvmbugs at cs.uiuc.edu


Consider the following:

D code using C binding (much like C):
        auto i = LLVMInt32Type();
        auto t = LLVMStructType(&i, 1, 1);
        auto tmp = LLVMGetUndef(t);
        LLVMDumpType(LLVMTypeOf(tmp));
        uint idx = 0;
        tmp = LLVMConstInsertValue(tmp, LLVMConstInt(i, 0, 0), &idx, 1);
        LLVMDumpType(LLVMTypeOf(tmp));

Dumps:
<{ i32 }>
{ i32 }

This patch is against revision 79806, but it is also present in 2.6, it's a
pretty serious bug, and I think it should be fixed in 2.6 as well.

===================================================================
--- ../lib/VMCore/ConstantFold.cpp      (revision 79806)
+++ ../lib/VMCore/ConstantFold.cpp      (working copy)
@@ -520,8 +520,8 @@
         UndefValue::get(MemberTy);
       Ops[i] = const_cast<Constant*>(Op);
     }
-    if (isa<StructType>(AggTy))
-      return ConstantStruct::get(Context, Ops);
+    if (const StructType* ST = dyn_cast<StructType>(AggTy))
+      return ConstantStruct::get(Context, Ops, ST->isPacked());
     else
       return ConstantArray::get(cast<ArrayType>(AggTy), Ops);
   }
@@ -549,8 +549,8 @@
         Constant::getNullValue(MemberTy);
       Ops[i] = const_cast<Constant*>(Op);
     }
-    if (isa<StructType>(AggTy))
-      return ConstantStruct::get(Context, Ops);
+    if (const StructType* ST = dyn_cast<StructType>(AggTy))
+      return ConstantStruct::get(Context, Ops, ST->isPacked());
     else
       return ConstantArray::get(cast<ArrayType>(AggTy), Ops);
   }
@@ -566,8 +566,8 @@
       Ops[i] = const_cast<Constant*>(Op);
     }
     Constant *C;
-    if (isa<StructType>(Agg->getType()))
-      C = ConstantStruct::get(Context, Ops);
+    if (const StructType* ST = dyn_cast<StructType>(Agg->getType()))
+      C = ConstantStruct::get(Context, Ops, ST->isPacked());
     else
       C = ConstantArray::get(cast<ArrayType>(Agg->getType()), Ops);
     return C;


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