[PATCH] D42489: [GlobalOpt] Emit fragments using field offsets from struct layout

[David Stenberg via Phabricator via llvm-commits]

dstenb created this revision.
dstenb added a reviewer: aprantl.
Herald added a subscriber: llvm-commits.

When creating the debug fragments for a SRA'd struct, use the fields'
offsets, taken from the struct layout, as the offsets for the resulting
fragments. This fixes an issue where GlobalOpt would emit fragments with
incorrect offsets for padded fields.

This should solve PR36016.


Repository:
  rL LLVM

https://reviews.llvm.org/D42489

Files:
  lib/Transforms/IPO/GlobalOpt.cpp
  test/DebugInfo/Generic/global-sra-struct.ll


Index: test/DebugInfo/Generic/global-sra-struct.ll
===================================================================
--- test/DebugInfo/Generic/global-sra-struct.ll
+++ test/DebugInfo/Generic/global-sra-struct.ll
@@ -24,7 +24,7 @@
 
 ; CHECK: ![[EL0]] = !DIGlobalVariableExpression(var: ![[VAR:.*]], expr: !DIExpression(DW_OP_LLVM_fragment, 0, 32))
 ; CHECK: ![[VAR]] = distinct !DIGlobalVariable(name: "static_struct"
-; CHECK: ![[EL1]] = !DIGlobalVariableExpression(var: ![[VAR]], expr: !DIExpression(DW_OP_LLVM_fragment, 32, 64))
+; CHECK: ![[EL1]] = !DIGlobalVariableExpression(var: ![[VAR]], expr: !DIExpression(DW_OP_LLVM_fragment, 64, 64))
 
 @static_struct = internal global %struct.mystruct zeroinitializer, align 8, !dbg !0
 
Index: lib/Transforms/IPO/GlobalOpt.cpp
===================================================================
--- lib/Transforms/IPO/GlobalOpt.cpp
+++ lib/Transforms/IPO/GlobalOpt.cpp
@@ -483,7 +483,6 @@
     StartAlignment = DL.getABITypeAlignment(GV->getType());
 
   if (StructType *STy = dyn_cast<StructType>(Ty)) {
-    uint64_t FragmentOffset = 0;
     unsigned NumElements = STy->getNumElements();
     NewGlobals.reserve(NumElements);
     const StructLayout &Layout = *DL.getStructLayout(STy);
@@ -509,10 +508,9 @@
         NGV->setAlignment(NewAlign);
 
       // Copy over the debug info for the variable.
-      FragmentOffset = alignTo(FragmentOffset, NewAlign);
       uint64_t Size = DL.getTypeSizeInBits(NGV->getValueType());
-      transferSRADebugInfo(GV, NGV, FragmentOffset, Size, NumElements);
-      FragmentOffset += Size;
+      uint64_t FragmentOffsetInBits = Layout.getElementOffsetInBits(i);
+      transferSRADebugInfo(GV, NGV, FragmentOffsetInBits, Size, NumElements);
     }
   } else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
     unsigned NumElements = STy->getNumElements();


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