[llvm] r373089 - [DebugInfo] Exclude memory location values as parameter entry values

[Djordje Todorovic via llvm-commits]

Author: djtodoro
Date: Fri Sep 27 06:52:43 2019
New Revision: 373089

URL: http://llvm.org/viewvc/llvm-project?rev=373089&view=rev
Log:
[DebugInfo] Exclude memory location values as parameter entry values

Abandon describing of loaded values due to safety concerns. Loaded
values are described as derefed memory location at caller point.
At callee we can unintentionally change that memory location which
would lead to different entry being printed value before and after
the memory location clobbering. This problem is described in
llvm.org/PR43343.

Patch by Nikola Prica

Differential Revision: https://reviews.llvm.org/D67717

Modified:
    llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
    llvm/trunk/lib/CodeGen/TargetInstrInfo.cpp
    llvm/trunk/test/DebugInfo/MIR/X86/dbgcall-site-interpretation.mir

Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp?rev=373089&r1=373088&r2=373089&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp (original)
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfExpression.cpp Fri Sep 27 06:52:43 2019
@@ -246,8 +246,8 @@ bool DwarfExpression::addMachineRegExpre
   // a call site parameter expression and if that expression is just a register
   // location, emit it with addBReg and offset 0, because we should emit a DWARF
   // expression representing a value, rather than a location.
-  if (!isMemoryLocation() && !HasComplexExpression && (!isParameterValue() ||
-                                                       isEntryValue())) {
+  if (!isMemoryLocation() && !HasComplexExpression &&
+      (!isParameterValue() || isEntryValue())) {
     for (auto &Reg : DwarfRegs) {
       if (Reg.DwarfRegNo >= 0)
         addReg(Reg.DwarfRegNo, Reg.Comment);
@@ -413,6 +413,9 @@ void DwarfExpression::addExpression(DIEx
       break;
     case dwarf::DW_OP_deref:
       assert(!isRegisterLocation());
+      // For more detailed explanation see llvm.org/PR43343.
+      assert(!isParameterValue() && "Parameter entry values should not be "
+                                    "dereferenced due to safety reasons.");
       if (!isMemoryLocation() && ::isMemoryLocation(ExprCursor))
         // Turning this into a memory location description makes the deref
         // implicit.

Modified: llvm/trunk/lib/CodeGen/TargetInstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/TargetInstrInfo.cpp?rev=373089&r1=373088&r2=373089&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/TargetInstrInfo.cpp (original)
+++ llvm/trunk/lib/CodeGen/TargetInstrInfo.cpp Fri Sep 27 06:52:43 2019
@@ -1133,18 +1133,6 @@ TargetInstrInfo::describeLoadedValue(con
   } else if (MI.isMoveImmediate()) {
     Op = &MI.getOperand(1);
     return ParamLoadedValue(*Op, Expr);
-  } else if (MI.hasOneMemOperand()) {
-    int64_t Offset;
-    const auto &TRI = MF->getSubtarget().getRegisterInfo();
-    const auto &TII = MF->getSubtarget().getInstrInfo();
-    const MachineOperand *BaseOp;
-
-    if (!TII->getMemOperandWithOffset(MI, BaseOp, Offset, TRI))
-      return None;
-
-    Expr = DIExpression::prepend(Expr, DIExpression::DerefAfter, Offset);
-    Op = BaseOp;
-    return ParamLoadedValue(*Op, Expr);
   }
 
   return None;

Modified: llvm/trunk/test/DebugInfo/MIR/X86/dbgcall-site-interpretation.mir
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/MIR/X86/dbgcall-site-interpretation.mir?rev=373089&r1=373088&r2=373089&view=diff
==============================================================================
--- llvm/trunk/test/DebugInfo/MIR/X86/dbgcall-site-interpretation.mir (original)
+++ llvm/trunk/test/DebugInfo/MIR/X86/dbgcall-site-interpretation.mir Fri Sep 27 06:52:43 2019
@@ -21,10 +21,8 @@
 # CHECK-NEXT:     DW_AT_low_pc
 # CHECK-EMPTY:
 # CHECK-NEXT:     DW_TAG_GNU_call_site_parameter
-# CHECK-NEXT:       DW_AT_location      (DW_OP_reg2 RCX)
-# CHECK-NEXT:       DW_AT_GNU_call_site_value   (DW_OP_fbreg +8, DW_OP_deref)
-# CHECK-EMPTY:
-# CHECK-NEXT:     DW_TAG_GNU_call_site_parameter
+# RCX loads memory location. We can't rely that memory location won't be changed.
+# CHECK-NOT:       DW_AT_location      (DW_OP_reg2 RCX)
 # CHECK-NEXT:       DW_AT_location      (DW_OP_reg4 RSI)
 # CHECK-NEXT:       DW_AT_GNU_call_site_value   (DW_OP_lit4)
 # CHECK-EMPTY: