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
// 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);
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.
} 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;
# 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: