From: Djordje Todorovic <djordje.todorovic@rt-rk.com>
Date: Fri, 27 Sep 2019 13:52:43 +0000 (+0000)
Subject: [DebugInfo] Exclude memory location values as parameter entry values
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=bc913bfd017612478f055f65d2e11cf0252abb6e;p=llvm

[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@373089 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index 52e5109dbf9..ea42e60344d 100644
--- a/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -246,8 +246,8 @@ bool DwarfExpression::addMachineRegExpression(const TargetRegisterInfo &TRI,
   // 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(DIExpressionCursor &&ExprCursor,
       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.
diff --git a/lib/CodeGen/TargetInstrInfo.cpp b/lib/CodeGen/TargetInstrInfo.cpp
index 0e9eb77ea26..2108fc6fecf 100644
--- a/lib/CodeGen/TargetInstrInfo.cpp
+++ b/lib/CodeGen/TargetInstrInfo.cpp
@@ -1133,18 +1133,6 @@ TargetInstrInfo::describeLoadedValue(const MachineInstr &MI) const {
   } 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;
diff --git a/test/DebugInfo/MIR/X86/dbgcall-site-interpretation.mir b/test/DebugInfo/MIR/X86/dbgcall-site-interpretation.mir
index 70c5501ff42..f4857ccd7e8 100644
--- a/test/DebugInfo/MIR/X86/dbgcall-site-interpretation.mir
+++ b/test/DebugInfo/MIR/X86/dbgcall-site-interpretation.mir
@@ -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: