[DebugInfo] Describe size of spilled values in call site params

A call site parameter description of a memory operand needs to
unambiguously convey the size of the operand to prevent incorrect entry
value evaluation.

Thanks for David Stenberg for pointing this issue out!

diff --git a/llvm/lib/CodeGen/TargetInstrInfo.cpp b/llvm/lib/CodeGen/TargetInstrInfo.cpp
index 2b987da..d7a02eb 100644 (file)
--- a/llvm/lib/CodeGen/TargetInstrInfo.cpp
+++ b/llvm/lib/CodeGen/TargetInstrInfo.cpp
@@ -1150,7 +1150,11 @@ TargetInstrInfo::describeLoadedValue(const MachineInstr &MI) const {
     if (!TII->getMemOperandWithOffset(MI, BaseOp, Offset, TRI))
       return None;
 
-    Expr = DIExpression::prepend(Expr, DIExpression::DerefAfter, Offset);
+    SmallVector<uint64_t, 8> Ops;
+    DIExpression::appendOffset(Ops, Offset);
+    Ops.push_back(dwarf::DW_OP_deref_size);
+    Ops.push_back(MMO->getSize());
+    Expr = DIExpression::prependOpcodes(Expr, Ops);
     return ParamLoadedValue(*BaseOp, Expr);
   }
 

diff --git a/llvm/test/DebugInfo/MIR/X86/dbg-call-site-spilled-arg.mir b/llvm/test/DebugInfo/MIR/X86/dbg-call-site-spilled-arg.mir
index 26ea062..373b484 100644 (file)
--- a/llvm/test/DebugInfo/MIR/X86/dbg-call-site-spilled-arg.mir
+++ b/llvm/test/DebugInfo/MIR/X86/dbg-call-site-spilled-arg.mir
@@ -22,7 +22,7 @@
 
 # CHECK-LABEL: DW_TAG_call_site_parameter
 # CHECK-NEXT:    DW_AT_location (DW_OP_reg5 RDI)
-# CHECK-NEXT:    DW_AT_call_value (DW_OP_fbreg -44, DW_OP_deref)
+# CHECK-NEXT:    DW_AT_call_value (DW_OP_fbreg -44, DW_OP_deref_size 0x4)
 
 --- |
   ; ModuleID = 'spill.cc'