[RISCV] Add CFI directives for RISCV prologue/epilog.

In order to generate correct debug frame information, it needs to
generate CFI information in prologue and epilog.

Differential Revision: https://reviews.llvm.org/D61773

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@363120 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/RISCV/MCTargetDesc/RISCVMCAsmInfo.cpp

@@ -21,6 +21,7 @@ RISCVMCAsmInfo::RISCVMCAsmInfo(const Triple &TT) {
   CommentString = "#";
   AlignmentIsInBytes = false;
   SupportsDebugInformation = true;
+  ExceptionsType = ExceptionHandling::DwarfCFI;
   Data16bitsDirective = "\t.half\t";
   Data32bitsDirective = "\t.word\t";
 }

lib/Target/RISCV/MCTargetDesc/RISCVMCTargetDesc.cpp

@@ -50,7 +50,13 @@ static MCRegisterInfo *createRISCVMCRegisterInfo(const Triple &TT) {
 
 static MCAsmInfo *createRISCVMCAsmInfo(const MCRegisterInfo &MRI,
                                        const Triple &TT) {
-  return new RISCVMCAsmInfo(TT);
+  MCAsmInfo *MAI = new RISCVMCAsmInfo(TT);
+
+  unsigned SP = MRI.getDwarfRegNum(RISCV::X2, true);
+  MCCFIInstruction Inst = MCCFIInstruction::createDefCfa(nullptr, SP, 0);
+  MAI->addInitialFrameState(Inst);
+
+  return MAI;
 }
 
 static MCSubtargetInfo *createRISCVMCSubtargetInfo(const Triple &TT,

lib/Target/RISCV/RISCVFrameLowering.cpp

@@ -18,6 +18,7 @@
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/RegisterScavenging.h"
+#include "llvm/MC/MCDwarf.h"
 
 using namespace llvm;
 
@@ -96,6 +97,8 @@ void RISCVFrameLowering::emitPrologue(MachineFunction &MF,
 
   MachineFrameInfo &MFI = MF.getFrameInfo();
   auto *RVFI = MF.getInfo<RISCVMachineFunctionInfo>();
+  const RISCVRegisterInfo *RI = STI.getRegisterInfo();
+  const RISCVInstrInfo *TII = STI.getInstrInfo();
   MachineBasicBlock::iterator MBBI = MBB.begin();
 
   unsigned FPReg = getFPReg(STI);
@@ -119,6 +122,12 @@ void RISCVFrameLowering::emitPrologue(MachineFunction &MF,
   // Allocate space on the stack if necessary.
   adjustReg(MBB, MBBI, DL, SPReg, SPReg, -StackSize, MachineInstr::FrameSetup);
 
+  // Emit ".cfi_def_cfa_offset StackSize"
+  unsigned CFIIndex = MF.addFrameInst(
+      MCCFIInstruction::createDefCfaOffset(nullptr, -StackSize));
+  BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
+      .addCFIIndex(CFIIndex);
+
   // The frame pointer is callee-saved, and code has been generated for us to
   // save it to the stack. We need to skip over the storing of callee-saved
   // registers as the frame pointer must be modified after it has been saved
@@ -128,10 +137,28 @@ void RISCVFrameLowering::emitPrologue(MachineFunction &MF,
   const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
   std::advance(MBBI, CSI.size());
 
+  // Iterate over list of callee-saved registers and emit .cfi_offset
+  // directives.
+  for (const auto &Entry : CSI) {
+    int64_t Offset = MFI.getObjectOffset(Entry.getFrameIdx());
+    unsigned Reg = Entry.getReg();
+    unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createOffset(
+        nullptr, RI->getDwarfRegNum(Reg, true), Offset));
+    BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
+        .addCFIIndex(CFIIndex);
+  }
+
   // Generate new FP.
-  if (hasFP(MF))
+  if (hasFP(MF)) {
     adjustReg(MBB, MBBI, DL, FPReg, SPReg,
               StackSize - RVFI->getVarArgsSaveSize(), MachineInstr::FrameSetup);
+
+    // Emit ".cfi_def_cfa $fp, 0"
+    unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createDefCfa(
+        nullptr, RI->getDwarfRegNum(FPReg, true), 0));
+    BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
+        .addCFIIndex(CFIIndex);
+  }
 }
 
 void RISCVFrameLowering::emitEpilogue(MachineFunction &MF,
@@ -141,6 +168,7 @@ void RISCVFrameLowering::emitEpilogue(MachineFunction &MF,
   MachineFrameInfo &MFI = MF.getFrameInfo();
   auto *RVFI = MF.getInfo<RISCVMachineFunctionInfo>();
   DebugLoc DL = MBBI->getDebugLoc();
+  const RISCVInstrInfo *TII = STI.getInstrInfo();
   unsigned FPReg = getFPReg(STI);
   unsigned SPReg = getSPReg(STI);
 
@@ -150,19 +178,58 @@ void RISCVFrameLowering::emitEpilogue(MachineFunction &MF,
   auto LastFrameDestroy = std::prev(MBBI, MFI.getCalleeSavedInfo().size());
 
   uint64_t StackSize = MFI.getStackSize();
+  uint64_t FPOffset = StackSize - RVFI->getVarArgsSaveSize();
 
   // Restore the stack pointer using the value of the frame pointer. Only
   // necessary if the stack pointer was modified, meaning the stack size is
   // unknown.
   if (RI->needsStackRealignment(MF) || MFI.hasVarSizedObjects()) {
     assert(hasFP(MF) && "frame pointer should not have been eliminated");
-    adjustReg(MBB, LastFrameDestroy, DL, SPReg, FPReg,
-              -StackSize + RVFI->getVarArgsSaveSize(),
+    adjustReg(MBB, LastFrameDestroy, DL, SPReg, FPReg, -FPOffset,
               MachineInstr::FrameDestroy);
   }
 
+  if (hasFP(MF)) {
+    // To find the instruction restoring FP from stack.
+    for (auto &I = LastFrameDestroy; I != MBBI; ++I) {
+      if (I->mayLoad() && I->getOperand(0).isReg()) {
+        unsigned DestReg = I->getOperand(0).getReg();
+        if (DestReg == FPReg) {
+          // If there is frame pointer, after restoring $fp registers, we
+          // need adjust CFA to ($sp - FPOffset).
+          // Emit ".cfi_def_cfa $sp, -FPOffset"
+          unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createDefCfa(
+              nullptr, RI->getDwarfRegNum(SPReg, true), -FPOffset));
+          BuildMI(MBB, std::next(I), DL,
+                  TII->get(TargetOpcode::CFI_INSTRUCTION))
+              .addCFIIndex(CFIIndex);
+          break;
+        }
+      }
+    }
+  }
+
+  // Add CFI directives for callee-saved registers.
+  const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
+  // Iterate over list of callee-saved registers and emit .cfi_restore
+  // directives.
+  for (const auto &Entry : CSI) {
+    unsigned Reg = Entry.getReg();
+    unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createRestore(
+        nullptr, RI->getDwarfRegNum(Reg, true)));
+    BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
+        .addCFIIndex(CFIIndex);
+  }
+
   // Deallocate stack
   adjustReg(MBB, MBBI, DL, SPReg, SPReg, StackSize, MachineInstr::FrameDestroy);
+
+  // After restoring $sp, we need to adjust CFA to $(sp + 0)
+  // Emit ".cfi_def_cfa_offset 0"
+  unsigned CFIIndex =
+      MF.addFrameInst(MCCFIInstruction::createDefCfaOffset(nullptr, 0));
+  BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
+      .addCFIIndex(CFIIndex);
 }
 
 int RISCVFrameLowering::getFrameIndexReference(const MachineFunction &MF,

test/CodeGen/RISCV/frame-info.ll

@@ -0,0 +1,66 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv32 < %s | FileCheck -check-prefix=RV32 %s
+; RUN: llc -mtriple=riscv64 < %s | FileCheck -check-prefix=RV64 %s
+
+define void @foo(i32 signext %size) {
+; RV32-LABEL: foo:
+; RV32:       # %bb.0: # %entry
+; RV32-NEXT:    addi sp, sp, -16
+; RV32-NEXT:    .cfi_def_cfa_offset 16
+; RV32-NEXT:    sw ra, 12(sp)
+; RV32-NEXT:    sw s0, 8(sp)
+; RV32-NEXT:    .cfi_offset ra, -4
+; RV32-NEXT:    .cfi_offset s0, -8
+; RV32-NEXT:    addi s0, sp, 16
+; RV32-NEXT:    .cfi_def_cfa s0, 0
+; RV32-NEXT:    addi a0, a0, 15
+; RV32-NEXT:    andi a0, a0, -16
+; RV32-NEXT:    sub a0, sp, a0
+; RV32-NEXT:    mv sp, a0
+; RV32-NEXT:    call bar
+; RV32-NEXT:    addi sp, s0, -16
+; RV32-NEXT:    lw s0, 8(sp)
+; RV32-NEXT:    .cfi_def_cfa sp, 16
+; RV32-NEXT:    lw ra, 12(sp)
+; RV32-NEXT:    .cfi_restore ra
+; RV32-NEXT:    .cfi_restore s0
+; RV32-NEXT:    addi sp, sp, 16
+; RV32-NEXT:    .cfi_def_cfa_offset 0
+; RV32-NEXT:    ret
+;
+; RV64-LABEL: foo:
+; RV64:       # %bb.0: # %entry
+; RV64-NEXT:    addi sp, sp, -16
+; RV64-NEXT:    .cfi_def_cfa_offset 16
+; RV64-NEXT:    sd ra, 8(sp)
+; RV64-NEXT:    sd s0, 0(sp)
+; RV64-NEXT:    .cfi_offset ra, -8
+; RV64-NEXT:    .cfi_offset s0, -16
+; RV64-NEXT:    addi s0, sp, 16
+; RV64-NEXT:    .cfi_def_cfa s0, 0
+; RV64-NEXT:    addi a1, zero, 1
+; RV64-NEXT:    slli a1, a1, 33
+; RV64-NEXT:    addi a1, a1, -16
+; RV64-NEXT:    slli a0, a0, 32
+; RV64-NEXT:    srli a0, a0, 32
+; RV64-NEXT:    addi a0, a0, 15
+; RV64-NEXT:    and a0, a0, a1
+; RV64-NEXT:    sub a0, sp, a0
+; RV64-NEXT:    mv sp, a0
+; RV64-NEXT:    call bar
+; RV64-NEXT:    addi sp, s0, -16
+; RV64-NEXT:    ld s0, 0(sp)
+; RV64-NEXT:    .cfi_def_cfa sp, 16
+; RV64-NEXT:    ld ra, 8(sp)
+; RV64-NEXT:    .cfi_restore ra
+; RV64-NEXT:    .cfi_restore s0
+; RV64-NEXT:    addi sp, sp, 16
+; RV64-NEXT:    .cfi_def_cfa_offset 0
+; RV64-NEXT:    ret
+entry:
+  %0 = alloca i8, i32 %size, align 16
+  call void @bar(i8* nonnull %0) #2
+  ret void
+}
+
+declare void @bar(i8*)