[ARM][Debug Info] Restore emitting of .cfi_def_cfa_offset for functions without stack frame

[sdmitrouk]

Summary

Looks like new code from rL222057 doesn't account for early return in ARMFrameLowering::emitPrologue, which leads to loosing .cfi_def_cfa_offset directive for functions without stack frame.

[asl]

This looks like a resonable fix. Tim @t.p.northover, any objections?

[sdmitrouk]

Add llvm-commits list...

[t.p.northover]

Looks reasonable to me too. Sorry about that.

Tim.

llvm/trunk/lib/Target/ARM/ARMFrameLowering.cpp

void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
   int D8SpillFI = 0;
 
   // All calls are tail calls in GHC calling conv, and functions have no
   // prologue/epilogue.
   if (MF.getFunction()->getCallingConv() == CallingConv::GHC)
     return;
 
   StackAdjustingInsts DefCFAOffsetCandidates;
+  bool HasFP = hasFP(MF);
 
   // Allocate the vararg register save area.
   if (ArgRegsSaveSize) {
     emitSPUpdate(isARM, MBB, MBBI, dl, TII, -ArgRegsSaveSize,
                  MachineInstr::FrameSetup);
     DefCFAOffsetCandidates.addInst(std::prev(MBBI), ArgRegsSaveSize, true);
   }
 
   if (!AFI->hasStackFrame() &&
       (!STI.isTargetWindows() || !WindowsRequiresStackProbe(MF, NumBytes))) {
     if (NumBytes - ArgRegsSaveSize != 0) {
       emitSPUpdate(isARM, MBB, MBBI, dl, TII, -(NumBytes - ArgRegsSaveSize),
                    MachineInstr::FrameSetup);
       DefCFAOffsetCandidates.addInst(std::prev(MBBI),
                                      NumBytes - ArgRegsSaveSize, true);
     }
+    DefCFAOffsetCandidates.emitDefCFAOffsets(MMI, MBB, dl, TII, HasFP);
     return;
   }
 
   // Determine spill area sizes.
   for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
     unsigned Reg = CSI[i].getReg();
     int FI = CSI[i].getFrameIdx();
     switch (Reg) {
void ARMFrameLowering::emitPrologue(MachineFunction &MF) const {
   // Move past area 1.
   MachineBasicBlock::iterator LastPush = MBB.end(), GPRCS1Push, GPRCS2Push;
   if (GPRCS1Size > 0) {
     GPRCS1Push = LastPush = MBBI++;
     DefCFAOffsetCandidates.addInst(LastPush, GPRCS1Size, true);
   }
 
   // Determine starting offsets of spill areas.
-  bool HasFP = hasFP(MF);
   unsigned GPRCS1Offset = NumBytes - ArgRegsSaveSize - GPRCS1Size;
   unsigned GPRCS2Offset = GPRCS1Offset - GPRCS2Size;
   unsigned DPRAlign = DPRCSSize ? std::min(8U, Align) : 4U;
   unsigned DPRGapSize = (GPRCS1Size + GPRCS2Size + ArgRegsSaveSize) % DPRAlign;
   unsigned DPRCSOffset = GPRCS2Offset - DPRGapSize - DPRCSSize;
   int FramePtrOffsetInPush = 0;
   if (HasFP) {
     FramePtrOffsetInPush =

llvm/trunk/test/CodeGen/ARM/debug-info-no-frame.ll

+; RUN: llc -mtriple=armv7-none-linux-gnueabihf < %s -o - | FileCheck %s
+
+; Function Attrs: nounwind
+define void @need_cfi_def_cfa_offset() #0 {
+; CHECK-LABEL: need_cfi_def_cfa_offset:
+; CHECK: sub  sp, sp, #4
+; CHECK: .cfi_def_cfa_offset 4
+entry:
+  %Depth = alloca i32, align 4
+  call void @llvm.dbg.declare(metadata i32* %Depth, metadata !9, metadata !10), !dbg !11
+  store i32 2, i32* %Depth, align 4, !dbg !11
+  ret void, !dbg !12
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+attributes #0 = { nounwind }
+attributes #1 = { nounwind readnone }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!7, !8}
+
+!0 = !MDCompileUnit(language: DW_LANG_C99, file: !1, producer: "", isOptimized: false)
+!1 = !MDFile(filename: "file.c", directory: "/dir")
+!2 = !{}
+!3 = !MDSubprogram(name: "need_cfi_def_cfa_offset", scope: !1, file: !1, line: 1, type: !4, isLocal: false, isDefinition: true, scopeLine: 2, isOptimized: false, function: void ()* @need_cfi_def_cfa_offset, variables: !2)
+!4 = !MDSubroutineType(types: !5)
+!5 = !{null}
+!6 = !MDBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!7 = !{i32 2, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !MDLocalVariable(tag: DW_TAG_auto_variable, name: "Depth", scope: !3, file: !1, line: 3, type: !6)
+!10 = !MDExpression()
+!11 = !MDLocation(line: 3, column: 9, scope: !3)
+!12 = !MDLocation(line: 7, column: 5, scope: !3)