[DWARF] Fix incorrect prologue end line record.

The prologue-end line record must be emitted after the last
instruction that is part of the function frame setup code and before
the instruction that marks the beginning of the function body.

Patch by Carlos Alberto Enciso!

Differential Revision: https://reviews.llvm.org/D41762

llvm-svn: 325143

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -1176,7 +1176,9 @@ void DwarfDebug::beginInstruction(const MachineInstr *MI) {
     return;
 
   // Check if source location changes, but ignore DBG_VALUE and CFI locations.
-  if (MI->isMetaInstruction())
+  // If the instruction is part of the function frame setup code, do not emit
+  // any line record, as there is no correspondence with any user code.
+  if (MI->isMetaInstruction() || MI->getFlag(MachineInstr::FrameSetup))
     return;
   const DebugLoc &DL = MI->getDebugLoc();
   // When we emit a line-0 record, we don't update PrevInstLoc; so look at

llvm/lib/Target/X86/X86ExpandPseudo.cpp

@@ -106,7 +106,7 @@ bool X86ExpandPseudo::ExpandMI(MachineBasicBlock &MBB,
     if (Offset) {
       // Check for possible merge with preceding ADD instruction.
       Offset += X86FL->mergeSPUpdates(MBB, MBBI, true);
-      X86FL->emitSPUpdate(MBB, MBBI, Offset, /*InEpilogue=*/true);
+      X86FL->emitSPUpdate(MBB, MBBI, DL, Offset, /*InEpilogue=*/true);
     }
 
     // Jump to label or value in register.
@@ -186,7 +186,7 @@ bool X86ExpandPseudo::ExpandMI(MachineBasicBlock &MBB,
   case X86::IRET: {
     // Adjust stack to erase error code
     int64_t StackAdj = MBBI->getOperand(0).getImm();
-    X86FL->emitSPUpdate(MBB, MBBI, StackAdj, true);
+    X86FL->emitSPUpdate(MBB, MBBI, DL, StackAdj, true);
     // Replace pseudo with machine iret
     BuildMI(MBB, MBBI, DL,
             TII->get(STI->is64Bit() ? X86::IRET64 : X86::IRET32));
@@ -210,7 +210,7 @@ bool X86ExpandPseudo::ExpandMI(MachineBasicBlock &MBB,
       // A ret can only handle immediates as big as 2**16-1.  If we need to pop
       // off bytes before the return address, we must do it manually.
       BuildMI(MBB, MBBI, DL, TII->get(X86::POP32r)).addReg(X86::ECX, RegState::Define);
-      X86FL->emitSPUpdate(MBB, MBBI, StackAdj, /*InEpilogue=*/true);
+      X86FL->emitSPUpdate(MBB, MBBI, DL, StackAdj, /*InEpilogue=*/true);
       BuildMI(MBB, MBBI, DL, TII->get(X86::PUSH32r)).addReg(X86::ECX);
       MIB = BuildMI(MBB, MBBI, DL, TII->get(X86::RETL));
     }

llvm/lib/Target/X86/X86FrameLowering.cpp

@@ -248,14 +248,14 @@ flagsNeedToBePreservedBeforeTheTerminators(const MachineBasicBlock &MBB) {
 /// stack pointer by a constant value.
 void X86FrameLowering::emitSPUpdate(MachineBasicBlock &MBB,
                                     MachineBasicBlock::iterator &MBBI,
+                                    const DebugLoc &DL,
                                     int64_t NumBytes, bool InEpilogue) const {
   bool isSub = NumBytes < 0;
   uint64_t Offset = isSub ? -NumBytes : NumBytes;
   MachineInstr::MIFlag Flag =
       isSub ? MachineInstr::FrameSetup : MachineInstr::FrameDestroy;
 
   uint64_t Chunk = (1LL << 31) - 1;
-  DebugLoc DL = MBB.findDebugLoc(MBBI);
 
   if (Offset > Chunk) {
     // Rather than emit a long series of instructions for large offsets,
@@ -998,7 +998,7 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF,
       Fn.arg_size() == 2) {
     StackSize += 8;
     MFI.setStackSize(StackSize);
-    emitSPUpdate(MBB, MBBI, -8, /*InEpilogue=*/false);
+    emitSPUpdate(MBB, MBBI, DL, -8, /*InEpilogue=*/false);
   }
 
   // If this is x86-64 and the Red Zone is not disabled, if we are a leaf
@@ -1259,7 +1259,7 @@ void X86FrameLowering::emitPrologue(MachineFunction &MF,
       MBB.insert(MBBI, MI);
     }
   } else if (NumBytes) {
-    emitSPUpdate(MBB, MBBI, -(int64_t)NumBytes, /*InEpilogue=*/false);
+    emitSPUpdate(MBB, MBBI, DL, -(int64_t)NumBytes, /*InEpilogue=*/false);
   }
 
   if (NeedsWinCFI && NumBytes) {
@@ -1649,7 +1649,7 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
     }
   } else if (NumBytes) {
     // Adjust stack pointer back: ESP += numbytes.
-    emitSPUpdate(MBB, MBBI, NumBytes, /*InEpilogue=*/true);
+    emitSPUpdate(MBB, MBBI, DL, NumBytes, /*InEpilogue=*/true);
     --MBBI;
   }
 
@@ -1669,7 +1669,7 @@ void X86FrameLowering::emitEpilogue(MachineFunction &MF,
     if (Offset) {
       // Check for possible merge with preceding ADD instruction.
       Offset += mergeSPUpdates(MBB, Terminator, true);
-      emitSPUpdate(MBB, Terminator, Offset, /*InEpilogue=*/true);
+      emitSPUpdate(MBB, Terminator, DL, Offset, /*InEpilogue=*/true);
     }
   }
 }

llvm/lib/Target/X86/X86FrameLowering.h

@@ -125,7 +125,7 @@ class X86FrameLowering : public TargetFrameLowering {
   /// Emit a series of instructions to increment / decrement the stack
   /// pointer by a constant value.
   void emitSPUpdate(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
-                    int64_t NumBytes, bool InEpilogue) const;
+                    const DebugLoc &DL, int64_t NumBytes, bool InEpilogue) const;
 
   /// Check that LEA can be used on SP in an epilogue sequence for \p MF.
   bool canUseLEAForSPInEpilogue(const MachineFunction &MF) const;

llvm/test/DebugInfo/COFF/types-array.ll

@@ -73,9 +73,9 @@
 ; CHECK:       OffsetInParent: 0
 ; CHECK:       BasePointerOffset: -20
 ; CHECK:       LocalVariableAddrRange {
-; CHECK:         OffsetStart: .text+0x3
+; CHECK:         OffsetStart: .text+0x6
 ; CHECK:         ISectStart: 0x0
-; CHECK:         Range: 0x36
+; CHECK:         Range: 0x33
 ; CHECK:       }
 ; CHECK:     }
 ; CHECK:     ProcEnd {

llvm/test/DebugInfo/X86/invalid-prologue-end.ll

@@ -0,0 +1,92 @@
+; RUN: llc -mtriple=x86_64-linux-gnu -filetype=asm %s -o - | FileCheck %s
+
+; The prologue-end line record must be emitted after the last instruction that
+; is part of the function frame setup code and before the instruction that marks
+; the beginning of the function body.
+;
+; For the given test, generated from:
+;
+; 1 extern int get_arg();
+; 2 extern void func(int x);
+; 3
+; 4 int main()
+; 5 {
+; 6   int a;
+; 7   func(get_arg());
+; 8 }
+; 9
+
+; The prologue-end line record is emitted with an incorrect associated address,
+; which causes a debugger to show the beginning of function body to be inside
+; the prologue.
+
+; This can be seen in the following trimmed assembler output:
+;
+; main:
+;   ...
+; # %bb.0:
+;   .loc	1 7 0 prologue_end
+;   pushq	%rax
+;   .cfi_def_cfa_offset 16
+;   callq	_Z7get_argv
+;   ...
+;   retq
+
+; The instruction 'pushq %rax' is part of the frame setup code.
+
+; The correct location for the prologue-end line information is just before
+; the call to '_Z7get_argv', as illustrated in the following trimmed
+; assembler output:
+;
+; main:
+;   ...
+; # %bb.0:
+;   pushq  %rax
+;   .cfi_def_cfa_offset 16
+;   .loc  1 7 0 prologue_end
+;   callq  _Z7get_argv
+;   ...
+;   retq
+
+; Check that the generated assembler matches the following sequence:
+
+; CHECK:      # %bb.0:
+; CHECK-NEXT:  	pushq	%rax
+; CHECK-NEXT:  	.cfi_def_cfa_offset 16
+; CHECK-NEXT: .Ltmp0:
+; CHECK-NEXT:  	.loc	1 7 8 prologue_end {{.*}}# invalid-prologue-end.cpp:7:8
+; CHECK-NEXT:  	callq	_Z7get_argv
+
+define i32 @main() #0 !dbg !7 {
+entry:
+  %a = alloca i32, align 4
+  call void @llvm.dbg.declare(metadata i32* %a, metadata !11, metadata !DIExpression()), !dbg !12
+  %call = call i32 @_Z7get_argv(), !dbg !13
+  call void @_Z4funci(i32 %call), !dbg !14
+  ret i32 0, !dbg !15
+}
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+declare void @_Z4funci(i32) #2
+declare i32 @_Z7get_argv() #2
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 7.0.0 (trunk 322269)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "invalid-prologue-end.cpp", directory: "/home/carlos/llvm-root/work")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{!"clang version 7.0.0 (trunk 322269)"}
+!7 = distinct !DISubprogram(name: "main", scope: !1, file: !1, line: 4, type: !8, isLocal: false, isDefinition: true, scopeLine: 5, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!8 = !DISubroutineType(types: !9)
+!9 = !{!10}
+!10 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!11 = !DILocalVariable(name: "a", scope: !7, file: !1, line: 6, type: !10)
+!12 = !DILocation(line: 6, column: 7, scope: !7)
+!13 = !DILocation(line: 7, column: 8, scope: !7)
+!14 = !DILocation(line: 7, column: 3, scope: !7)
+!15 = !DILocation(line: 8, column: 1, scope: !7)