[PATCH] D64971: [SafeStack] Insert the deref after the offset

[Petr Hosek via Phabricator via llvm-commits]

phosek updated this revision to Diff 210877.
phosek retitled this revision from "[SafeStack] Don't re-insert derefs for allocas in debug info" to "[SafeStack] Insert the deref after the offset".
phosek edited the summary of this revision.
phosek added a comment.

I've moved the `deref` after the offset calculation, tested this against our build and it's producing the expected DWARF output.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D64971/new/

https://reviews.llvm.org/D64971

Files:
  llvm/lib/Transforms/Utils/Local.cpp
  llvm/test/Transforms/SafeStack/X86/debug-loc2.ll


Index: llvm/test/Transforms/SafeStack/X86/debug-loc2.ll
===================================================================
--- llvm/test/Transforms/SafeStack/X86/debug-loc2.ll
+++ llvm/test/Transforms/SafeStack/X86/debug-loc2.ll
@@ -25,7 +25,7 @@
   tail call void @llvm.dbg.value(metadata i32* %x1, metadata !10, metadata !24), !dbg !16
 
 ; Supported dbg.value: rewritted based on the [[USP]] value.
-; CHECK: call void @llvm.dbg.value(metadata i8* %[[USP]], metadata ![[X1:.*]], metadata !DIExpression(DW_OP_deref, DW_OP_constu, 4, DW_OP_minus))
+; CHECK: call void @llvm.dbg.value(metadata i8* %[[USP]], metadata ![[X1:.*]], metadata !DIExpression(DW_OP_constu, 4, DW_OP_minus, DW_OP_deref))
   tail call void @llvm.dbg.value(metadata i32* %x1, metadata !10, metadata !15), !dbg !16
   call void @capture(i32* nonnull %x1), !dbg !17
 
@@ -33,7 +33,7 @@
 ; CHECK: call void @llvm.random.metadata.use(metadata ![[EMPTY]])
   call void @llvm.random.metadata.use(metadata i32* %x2)
 
-; CHECK: call void @llvm.dbg.value(metadata i8* %[[USP]], metadata ![[X2:.*]], metadata !DIExpression(DW_OP_deref, DW_OP_constu, 8, DW_OP_minus))
+; CHECK: call void @llvm.dbg.value(metadata i8* %[[USP]], metadata ![[X2:.*]], metadata !DIExpression(DW_OP_constu, 8, DW_OP_minus, DW_OP_deref))
   call void @llvm.dbg.value(metadata i32* %x2, metadata !12, metadata !15), !dbg !18
   call void @capture(i32* nonnull %x2), !dbg !19
   ret void, !dbg !20
Index: llvm/lib/Transforms/Utils/Local.cpp
===================================================================
--- llvm/lib/Transforms/Utils/Local.cpp
+++ llvm/lib/Transforms/Utils/Local.cpp
@@ -1591,13 +1591,13 @@
       DIExpr->getElement(0) != dwarf::DW_OP_deref)
     return;
 
-  // Insert the offset immediately after the first deref.
+  // Insert the offset before the reference.
   // We could just change the offset argument of dbg.value, but it's unsigned...
   if (Offset) {
     SmallVector<uint64_t, 4> Ops;
-    Ops.push_back(dwarf::DW_OP_deref);
     DIExpression::appendOffset(Ops, Offset);
     Ops.append(DIExpr->elements_begin() + 1, DIExpr->elements_end());
+    Ops.push_back(dwarf::DW_OP_deref);
     DIExpr = Builder.createExpression(Ops);
   }
 


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