Re: [llvm-commits] [127801] When an LLVM type has struct padding that overlaps with important fields of

[Duncan Sands]

Hi Chris, this breaks the Ada build since the TYPE_SIZE may not be a constant:

> +  if (TYPE_SIZE(type) == 0 ||
> +      PadStartBits >= int(TREE_INT_CST_LOW(TYPE_SIZE(type))) ||

I've attached a fix, which includes some other tweaks for arrays
(not very important) plus whitespace cleanup.

Ciao,

Duncan.

Index: gcc.llvm.master/gcc/llvm-types.cpp
===================================================================
--- gcc.llvm.master.orig/gcc/llvm-types.cpp	2007-05-31 15:09:52.000000000 +0200
+++ gcc.llvm.master/gcc/llvm-types.cpp	2007-05-31 15:17:38.000000000 +0200
@@ -526,12 +526,19 @@
   type = TYPE_MAIN_VARIANT(type);
 
   // If the type does not overlap, don't bother checking below.
-  if (TYPE_SIZE(type) == 0 ||
-      PadStartBits >= int(TREE_INT_CST_LOW(TYPE_SIZE(type))) ||
+
+  if (!TYPE_SIZE(type))
+    return false;
+
+  if (!isInt64(TYPE_SIZE(type), false))
+    // Variable sized or huge - be conservative.
+    return true;
+
+  if (PadStartBits >= (int64_t)getInt64(TYPE_SIZE(type), false) ||
       PadStartBits+PadSizeBits <= 0)
     return false;
 
-  
+
   switch (TREE_CODE(type)) {
   default:
     fprintf(stderr, "Unknown type to compare:\n");
@@ -550,9 +557,16 @@
     return true;
 
   case ARRAY_TYPE: {
-    unsigned EltSizeBits = TREE_INT_CST_LOW(TYPE_SIZE(TREE_TYPE(type)));
-    unsigned NumElts = getInt64(arrayLength(type), true);
-    unsigned OverlapElt = (unsigned)PadStartBits/EltSizeBits;
+    uint64_t EltSizeBits = getInt64(TYPE_SIZE(TREE_TYPE(type)), true);
+    uint64_t NumElts = getInt64(arrayLength(type), true);
+    uint64_t MaxElts = 1 + (uint64_t)(PadStartBits+PadSizeBits)/EltSizeBits;
+
+    if (MaxElts < NumElts)
+      NumElts = MaxElts;
+
+    // Don't waste time on large arrays.
+    if (NumElts > 256)
+      return true;
 
     // Check each element for overlap.  This is inelegant, but effective.
     for (unsigned i = 0; i != NumElts; ++i)
@@ -574,7 +588,7 @@
       return GCCTypeOverlapsWithPadding(TREE_TYPE(Field),
                                         PadStartBits, PadSizeBits);
     }
-    
+
     // See if any elements overlap.
     for (tree Field = TYPE_FIELDS(type); Field; Field = TREE_CHAIN(Field)) {
       if (TREE_CODE(Field) != FIELD_DECL) continue;
@@ -587,14 +601,14 @@
 
     return false;
   }
-    
+
   case RECORD_TYPE: 
     for (tree Field = TYPE_FIELDS(type); Field; Field = TREE_CHAIN(Field)) {
       if (TREE_CODE(Field) != FIELD_DECL) continue;
-      
+
       if (TREE_CODE(DECL_FIELD_OFFSET(Field)) != INTEGER_CST)
         return true;
-      
+
       unsigned FieldBitOffset = getFieldOffsetInBits(Field);
       if (GCCTypeOverlapsWithPadding(TREE_TYPE(Field), 
                                      PadStartBits-FieldBitOffset, PadSizeBits))

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