[DWARF] Store CFA value on DW_CFA_remember_state

Previously, CFA_remember_state stored only the register locations but ignored the CFA value. This needs also to be remembered and restored for correct behavior. The problem occurs, e.g., on functions with multiple epilogues, where the CFA value after the first epilogue is becomes wrong.

Reviewed By: #debug-info, MaskRay

Differential Revision: https://reviews.llvm.org/D140338

diff --git a/llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp
index 1b71f4b..aae1668 100644 (file)
--- a/llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp
@@ -514,7 +514,8 @@ CFIProgram::Instruction::getOperandAsSigned(const CFIProgram &CFIP,
 
 Error UnwindTable::parseRows(const CFIProgram &CFIP, UnwindRow &Row,
                              const RegisterLocations *InitialLocs) {
-  std::vector<RegisterLocations> RegisterStates;
+  // State consists of CFA value and register locations.
+  std::vector<std::pair<UnwindLocation, RegisterLocations>> States;
   for (const CFIProgram::Instruction &Inst : CFIP) {
     switch (Inst.Opcode) {
     case dwarf::DW_CFA_set_loc: {
@@ -597,16 +598,18 @@ Error UnwindTable::parseRows(const CFIProgram &CFIP, UnwindRow &Row,
       break;
 
     case dwarf::DW_CFA_remember_state:
-      RegisterStates.push_back(Row.getRegisterLocations());
+      States.push_back(
+          std::make_pair(Row.getCFAValue(), Row.getRegisterLocations()));
       break;
 
     case dwarf::DW_CFA_restore_state:
-      if (RegisterStates.empty())
+      if (States.empty())
         return createStringError(errc::invalid_argument,
                                  "DW_CFA_restore_state without a matching "
                                  "previous DW_CFA_remember_state");
-      Row.getRegisterLocations() = RegisterStates.back();
-      RegisterStates.pop_back();
+      Row.getCFAValue() = States.back().first;
+      Row.getRegisterLocations() = States.back().second;
+      States.pop_back();
       break;
 
     case dwarf::DW_CFA_GNU_window_save:

diff --git a/llvm/unittests/DebugInfo/DWARF/DWARFDebugFrameTest.cpp b/llvm/unittests/DebugInfo/DWARF/DWARFDebugFrameTest.cpp
index ebfba7c..d965531 100644 (file)
--- a/llvm/unittests/DebugInfo/DWARF/DWARFDebugFrameTest.cpp
+++ b/llvm/unittests/DebugInfo/DWARF/DWARFDebugFrameTest.cpp
@@ -1143,16 +1143,22 @@ TEST(DWARFDebugFrame, UnwindTable_DW_CFA_remember_state) {
 
   // Make a CIE that has a valid CFA definition and a single register unwind
   // rule for register that we will verify is in all of the pushed rows.
-  EXPECT_THAT_ERROR(parseCFI(TestCIE, {dwarf::DW_CFA_def_cfa, 12, 32}),
+  constexpr uint8_t CFAOff1 = 32;
+  constexpr uint8_t CFAOff2 = 16;
+  constexpr uint8_t Reg1 = 14;
+  constexpr uint8_t Reg2 = 15;
+  constexpr uint8_t Reg3 = 16;
+
+  EXPECT_THAT_ERROR(parseCFI(TestCIE, {dwarf::DW_CFA_def_cfa, 12, CFAOff1}),
                     Succeeded());
 
   // Make a FDE with DWARF call frame instruction opcodes that encodes the
   // follwing rows:
-  // 0x1000: CFA=reg12+32: Reg1=[CFA-8]
-  // 0x1004: CFA=reg12+32: Reg1=[CFA-8] Reg2=[CFA-16]
-  // 0x1008: CFA=reg12+32: Reg1=[CFA-8] Reg2=[CFA-16] Reg3=[CFA-24]
-  // 0x100C: CFA=reg12+32: Reg1=[CFA-8] Reg2=[CFA-16]
-  // 0x1010: CFA=reg12+32: Reg1=[CFA-8]
+  // 0x1000: CFA=reg12+CFAOff1: Reg1=[CFA-8]
+  // 0x1004: CFA=reg12+CFAOff1: Reg1=[CFA-8] Reg2=[CFA-16]
+  // 0x1008: CFA=reg12+CFAOff2: Reg1=[CFA-8] Reg2=[CFA-16] Reg3=[CFA-24]
+  // 0x100C: CFA=reg12+CFAOff1: Reg1=[CFA-8] Reg2=[CFA-16]
+  // 0x1010: CFA=reg12+CFAOff1: Reg1=[CFA-8]
   // This state machine will:
   //  - set Reg1 location
   //  - push a row (from DW_CFA_advance_loc)
@@ -1160,6 +1166,7 @@ TEST(DWARFDebugFrame, UnwindTable_DW_CFA_remember_state) {
   //  - set Reg2 location
   //  - push a row (from DW_CFA_advance_loc)
   //  - remember the state
+  //  - set CFA offset to CFAOff2
   //  - set Reg3 location
   //  - push a row (from DW_CFA_advance_loc)
   //  - remember the state where Reg1 and Reg2 were set
@@ -1167,14 +1174,12 @@ TEST(DWARFDebugFrame, UnwindTable_DW_CFA_remember_state) {
   //  - remember the state where only Reg1 was set
   //  - push a row (automatically at the end of instruction parsing)
   // Then we verify that all registers are correct in all generated rows.
-  constexpr uint8_t Reg1 = 14;
-  constexpr uint8_t Reg2 = 15;
-  constexpr uint8_t Reg3 = 16;
   EXPECT_THAT_ERROR(
       parseCFI(TestFDE,
                {dwarf::DW_CFA_offset | Reg1, 1, dwarf::DW_CFA_advance_loc | 4,
                 dwarf::DW_CFA_remember_state, dwarf::DW_CFA_offset | Reg2, 2,
                 dwarf::DW_CFA_advance_loc | 4, dwarf::DW_CFA_remember_state,
+                dwarf::DW_CFA_def_cfa_offset, CFAOff2,
                 dwarf::DW_CFA_offset | Reg3, 3, dwarf::DW_CFA_advance_loc | 4,
                 dwarf::DW_CFA_restore_state, dwarf::DW_CFA_advance_loc | 4,
                 dwarf::DW_CFA_restore_state}),
@@ -1206,18 +1211,28 @@ TEST(DWARFDebugFrame, UnwindTable_DW_CFA_remember_state) {
   const dwarf::UnwindTable &Rows = RowsOrErr.get();
   EXPECT_EQ(Rows.size(), 5u);
   EXPECT_EQ(Rows[0].getAddress(), 0x1000u);
+  EXPECT_EQ(Rows[0].getCFAValue(),
+            dwarf::UnwindLocation::createIsRegisterPlusOffset(12, CFAOff1));
   EXPECT_EQ(Rows[0].getRegisterLocations(), VerifyLocs1);
 
   EXPECT_EQ(Rows[1].getAddress(), 0x1004u);
+  EXPECT_EQ(Rows[1].getCFAValue(),
+            dwarf::UnwindLocation::createIsRegisterPlusOffset(12, CFAOff1));
   EXPECT_EQ(Rows[1].getRegisterLocations(), VerifyLocs2);
 
   EXPECT_EQ(Rows[2].getAddress(), 0x1008u);
+  EXPECT_EQ(Rows[2].getCFAValue(),
+            dwarf::UnwindLocation::createIsRegisterPlusOffset(12, CFAOff2));
   EXPECT_EQ(Rows[2].getRegisterLocations(), VerifyLocs3);
 
   EXPECT_EQ(Rows[3].getAddress(), 0x100Cu);
+  EXPECT_EQ(Rows[3].getCFAValue(),
+            dwarf::UnwindLocation::createIsRegisterPlusOffset(12, CFAOff1));
   EXPECT_EQ(Rows[3].getRegisterLocations(), VerifyLocs2);
 
   EXPECT_EQ(Rows[4].getAddress(), 0x1010u);
+  EXPECT_EQ(Rows[4].getCFAValue(),
+            dwarf::UnwindLocation::createIsRegisterPlusOffset(12, CFAOff1));
   EXPECT_EQ(Rows[4].getRegisterLocations(), VerifyLocs1);
 }