[mips] Fix 'jumpy' debug line info around calls.

[dsanders]

Summary

At the moment, address calculation is taking the debug line info from the
address node (e.g. TargetGlobalAddress). When a function is called multiple
times, this results in output of the form:

.loc $first_call_location
.. address calculation ..
.. function call ..
.. address calculation ..
.loc $second_call_location
.. function call ..
.loc $first_call_location
.. address calculation ..
.loc $third_call_location
.. function call ..

This patch makes address calculations for function calls take the debug line
info for the call node and results in output of the form:

.loc $first_call_location
.. address calculation ..
.. function call ..
.loc $second_call_location
.. address calculation ..
.. function call ..
.loc $third_call_location
.. address calculation ..
.. function call ..

All other address calculations continue to use the address node.

[dblaikie]

It'd be good to have an explicit test for this (in case the multiline test is ever refactored/removed to test in a different way) with an explicit mips triple (so that even people who's host architecture isn't mips will see this failure immediately if they regress this behavior).

[dsanders]

Added explicit test case (based on test/Debug/multiline.ll) and added
comments explaining that it's intended to test that 'jumpy' line info is not
emitted.

[dsanders]

Is this what you had in mind? I've essentially copied multiline.ll, added -mtriple=mips-linux-gnu, and explained the 'jumpy' line information problem.

[dblaikie]

In D7050#110731, @dsanders wrote:

Is this what you had in mind? I've essentially copied multiline.ll, added -mtriple=mips-linux-gnu, and explained the 'jumpy' line information problem.

More or less - I'd simplify it to only the basics needed (two function calls to the same function - I'd put them on different lines, because the test case isn't about interesting things that happen when they're on the same line, or when there's 3 of them, etc).

I might simplify the description a bit, but your description's fine too.

[dsanders]

Reduced the testcase to the minimum required (two functions rather than six and
functions are on different lines).

[dsanders]

Previous revision deleted a little too much and it started passing without the
fix. Brought back one more function call.

[dsanders]

On Wed, Jan 21, 2015 at 7:37 AM, Daniel Sanders <[e-mail]<mailto:[e-mail]>> wrote:
Previous revision deleted a little too much and it started passing without the
fix. Brought back one more function call.

Why were 2 calls insufficient?

The first spurious '.loc 3' we are looking for is always omitted because the previous call is on line 3 too. With a third call, a second spurious '.loc 3' will appear between the second and third calls.

From: David Blaikie [mailto:[e-mail]]
Sent: 21 January 2015 17:07
To: [e-mail]
Cc: Daniel Sanders; Vladimir Medic; [e-mail]; [e-mail]
Subject: Re: [PATCH] [mips] Fix 'jumpy' debug line info around calls.

[dsanders]

Test the .loc positioning more directly by matching the %call16 reloc.

[dsanders]

The extra nots/checks/suffixes don't seem important to the essence of this test.

I agree. I'll prune that in the commit.

I'll leave it to someone MIPS-y to sign off on the actual code change (unless you were only seeking review of the test case part of things & you're confident in the code change itself).

I'd normally wait for a full pre-commit sign-off regardless of my confidence level but it's a safe change and it should make the builder green again so I think it's best to make an exception.

---

From: David Blaikie [[e-mail]]
Sent: 22 January 2015 17:47
To: [e-mail]
Cc: Daniel Sanders; Vladimir Medic; [e-mail]; ehostunreach
Subject: Re: [PATCH] [mips] Fix 'jumpy' debug line info around calls.

lib/Target/Mips/Mips16ISelLowering.cpp

if (Subtarget.inMips16HardFloat()) {
     if (LookupHelper)
       Mips16HelperFunction =
         getMips16HelperFunction(CLI.RetTy, CLI.getArgs(), NeedMips16Helper);
   }
 
   SDValue JumpTarget = Callee;
 
   // T9 should contain the address of the callee function if
-  // -reloction-model=pic or it is an indirect call.
+  // -relocation-model=pic or it is an indirect call.
   if (IsPICCall || !GlobalOrExternal) {
     unsigned V0Reg = Mips::V0;
     if (NeedMips16Helper) {
       RegsToPass.push_front(std::make_pair(V0Reg, Callee));
       JumpTarget = DAG.getExternalSymbol(Mips16HelperFunction, getPointerTy());
       ExternalSymbolSDNode *S = cast<ExternalSymbolSDNode>(JumpTarget);
-      JumpTarget = getAddrGlobal(S, JumpTarget.getValueType(), DAG,
+      JumpTarget = getAddrGlobal(S, CLI.DL, JumpTarget.getValueType(), DAG,
                                  MipsII::MO_GOT, Chain,
                                  FuncInfo->callPtrInfo(S->getSymbol()));
     } else
       RegsToPass.push_front(std::make_pair((unsigned)Mips::T9, Callee));
   }
 
   Ops.push_back(JumpTarget);
 

lib/Target/Mips/MipsISelLowering.h

namespace llvm {
   protected:
     SDValue getGlobalReg(SelectionDAG &DAG, EVT Ty) const;
 
     // This method creates the following nodes, which are necessary for
     // computing a local symbol's address:
     //
     // (add (load (wrapper $gp, %got(sym)), %lo(sym))
     template <class NodeTy>
-    SDValue getAddrLocal(NodeTy *N, EVT Ty, SelectionDAG &DAG,
+    SDValue getAddrLocal(NodeTy *N, SDLoc DL, EVT Ty, SelectionDAG &DAG,
                          bool IsN32OrN64) const {
-      SDLoc DL(N);
       unsigned GOTFlag = IsN32OrN64 ? MipsII::MO_GOT_PAGE : MipsII::MO_GOT;
       SDValue GOT = DAG.getNode(MipsISD::Wrapper, DL, Ty, getGlobalReg(DAG, Ty),
                                 getTargetNode(N, Ty, DAG, GOTFlag));
       SDValue Load = DAG.getLoad(Ty, DL, DAG.getEntryNode(), GOT,
                                  MachinePointerInfo::getGOT(), false, false,
                                  false, 0);
       unsigned LoFlag = IsN32OrN64 ? MipsII::MO_GOT_OFST : MipsII::MO_ABS_LO;
       SDValue Lo = DAG.getNode(MipsISD::Lo, DL, Ty,
                                getTargetNode(N, Ty, DAG, LoFlag));
       return DAG.getNode(ISD::ADD, DL, Ty, Load, Lo);
     }
 
     // This method creates the following nodes, which are necessary for
     // computing a global symbol's address:
     //
     // (load (wrapper $gp, %got(sym)))
-    template<class NodeTy>
-    SDValue getAddrGlobal(NodeTy *N, EVT Ty, SelectionDAG &DAG,
+    template <class NodeTy>
+    SDValue getAddrGlobal(NodeTy *N, SDLoc DL, EVT Ty, SelectionDAG &DAG,
                           unsigned Flag, SDValue Chain,
                           const MachinePointerInfo &PtrInfo) const {
-      SDLoc DL(N);
       SDValue Tgt = DAG.getNode(MipsISD::Wrapper, DL, Ty, getGlobalReg(DAG, Ty),
                                 getTargetNode(N, Ty, DAG, Flag));
       return DAG.getLoad(Ty, DL, Chain, Tgt, PtrInfo, false, false, false, 0);
     }
 
     // This method creates the following nodes, which are necessary for
     // computing a global symbol's address in large-GOT mode:
     //
     // (load (wrapper (add %hi(sym), $gp), %lo(sym)))
-    template<class NodeTy>
-    SDValue getAddrGlobalLargeGOT(NodeTy *N, EVT Ty, SelectionDAG &DAG,
-                                  unsigned HiFlag, unsigned LoFlag,
-                                  SDValue Chain,
+    template <class NodeTy>
+    SDValue getAddrGlobalLargeGOT(NodeTy *N, SDLoc DL, EVT Ty,
+                                  SelectionDAG &DAG, unsigned HiFlag,
+                                  unsigned LoFlag, SDValue Chain,
                                   const MachinePointerInfo &PtrInfo) const {
-      SDLoc DL(N);
-      SDValue Hi = DAG.getNode(MipsISD::Hi, DL, Ty,
-                               getTargetNode(N, Ty, DAG, HiFlag));
+      SDValue Hi =
+          DAG.getNode(MipsISD::Hi, DL, Ty, getTargetNode(N, Ty, DAG, HiFlag));
       Hi = DAG.getNode(ISD::ADD, DL, Ty, Hi, getGlobalReg(DAG, Ty));
       SDValue Wrapper = DAG.getNode(MipsISD::Wrapper, DL, Ty, Hi,
                                     getTargetNode(N, Ty, DAG, LoFlag));
       return DAG.getLoad(Ty, DL, Chain, Wrapper, PtrInfo, false, false, false,
                          0);
     }
 
     // This method creates the following nodes, which are necessary for
     // computing a symbol's address in non-PIC mode:
     //
     // (add %hi(sym), %lo(sym))
-    template<class NodeTy>
-    SDValue getAddrNonPIC(NodeTy *N, EVT Ty, SelectionDAG &DAG) const {
-      SDLoc DL(N);
+    template <class NodeTy>
+    SDValue getAddrNonPIC(NodeTy *N, SDLoc DL, EVT Ty,
+                          SelectionDAG &DAG) const {
       SDValue Hi = getTargetNode(N, Ty, DAG, MipsII::MO_ABS_HI);
       SDValue Lo = getTargetNode(N, Ty, DAG, MipsII::MO_ABS_LO);
       return DAG.getNode(ISD::ADD, DL, Ty,
                          DAG.getNode(MipsISD::Hi, DL, Ty, Hi),
                          DAG.getNode(MipsISD::Lo, DL, Ty, Lo));
     }
 
     // This method creates the following nodes, which are necessary for
     // computing a symbol's address using gp-relative addressing:
     //
     // (add $gp, %gp_rel(sym))
-    template<class NodeTy>
-    SDValue getAddrGPRel(NodeTy *N, EVT Ty, SelectionDAG &DAG) const {
-      SDLoc DL(N);
+    template <class NodeTy>
+    SDValue getAddrGPRel(NodeTy *N, SDLoc DL, EVT Ty, SelectionDAG &DAG) const {
       assert(Ty == MVT::i32);
       SDValue GPRel = getTargetNode(N, Ty, DAG, MipsII::MO_GPREL);
       return DAG.getNode(ISD::ADD, DL, Ty,
                          DAG.getRegister(Mips::GP, Ty),
                          DAG.getNode(MipsISD::GPRel, DL, DAG.getVTList(Ty),
                                      GPRel));
     }
 

lib/Target/Mips/MipsISelLowering.cpp

SDValue MipsTargetLowering::lowerGlobalAddress(SDValue Op,
 
   if (getTargetMachine().getRelocationModel() != Reloc::PIC_ &&
       !Subtarget.isABI_N64()) {
     const MipsTargetObjectFile &TLOF =
       (const MipsTargetObjectFile&)getObjFileLowering();
 
     if (TLOF.IsGlobalInSmallSection(GV, getTargetMachine()))
       // %gp_rel relocation
-      return getAddrGPRel(N, Ty, DAG);
+      return getAddrGPRel(N, SDLoc(N), Ty, DAG);
 
     // %hi/%lo relocation
-    return getAddrNonPIC(N, Ty, DAG);
+    return getAddrNonPIC(N, SDLoc(N), Ty, DAG);
   }
 
   if (GV->hasInternalLinkage() || (GV->hasLocalLinkage() && !isa<Function>(GV)))
-    return getAddrLocal(N, Ty, DAG,
+    return getAddrLocal(N, SDLoc(N), Ty, DAG,
                         Subtarget.isABI_N32() || Subtarget.isABI_N64());
 
   if (LargeGOT)
-    return getAddrGlobalLargeGOT(N, Ty, DAG, MipsII::MO_GOT_HI16,
+    return getAddrGlobalLargeGOT(N, SDLoc(N), Ty, DAG, MipsII::MO_GOT_HI16,
                                  MipsII::MO_GOT_LO16, DAG.getEntryNode(),
                                  MachinePointerInfo::getGOT());
 
-  return getAddrGlobal(N, Ty, DAG,
+  return getAddrGlobal(N, SDLoc(N), Ty, DAG,
                        (Subtarget.isABI_N32() || Subtarget.isABI_N64())
                            ? MipsII::MO_GOT_DISP
                            : MipsII::MO_GOT16,
                        DAG.getEntryNode(), MachinePointerInfo::getGOT());
 }
 
 SDValue MipsTargetLowering::lowerBlockAddress(SDValue Op,
                                               SelectionDAG &DAG) const {
   BlockAddressSDNode *N = cast<BlockAddressSDNode>(Op);
   EVT Ty = Op.getValueType();
 
   if (getTargetMachine().getRelocationModel() != Reloc::PIC_ &&
       !Subtarget.isABI_N64())
-    return getAddrNonPIC(N, Ty, DAG);
+    return getAddrNonPIC(N, SDLoc(N), Ty, DAG);
 
-  return getAddrLocal(N, Ty, DAG,
+  return getAddrLocal(N, SDLoc(N), Ty, DAG,
                       Subtarget.isABI_N32() || Subtarget.isABI_N64());
 }
 
 SDValue MipsTargetLowering::
 lowerGlobalTLSAddress(SDValue Op, SelectionDAG &DAG) const
 {
   // If the relocation model is PIC, use the General Dynamic TLS Model or
   // Local Dynamic TLS model, otherwise use the Initial Exec or

 SDValue MipsTargetLowering::
 lowerJumpTable(SDValue Op, SelectionDAG &DAG) const
 {
   JumpTableSDNode *N = cast<JumpTableSDNode>(Op);
   EVT Ty = Op.getValueType();
 
   if (getTargetMachine().getRelocationModel() != Reloc::PIC_ &&
       !Subtarget.isABI_N64())
-    return getAddrNonPIC(N, Ty, DAG);
+    return getAddrNonPIC(N, SDLoc(N), Ty, DAG);
 
-  return getAddrLocal(N, Ty, DAG,
+  return getAddrLocal(N, SDLoc(N), Ty, DAG,
                       Subtarget.isABI_N32() || Subtarget.isABI_N64());
 }
 
 SDValue MipsTargetLowering::
 lowerConstantPool(SDValue Op, SelectionDAG &DAG) const
 {
   ConstantPoolSDNode *N = cast<ConstantPoolSDNode>(Op);
   EVT Ty = Op.getValueType();
 
   if (getTargetMachine().getRelocationModel() != Reloc::PIC_ &&
       !Subtarget.isABI_N64()) {
     const MipsTargetObjectFile &TLOF =
       (const MipsTargetObjectFile&)getObjFileLowering();
 
     if (TLOF.IsConstantInSmallSection(N->getConstVal(), getTargetMachine()))
       // %gp_rel relocation
-      return getAddrGPRel(N, Ty, DAG);
+      return getAddrGPRel(N, SDLoc(N), Ty, DAG);
 
-    return getAddrNonPIC(N, Ty, DAG);
+    return getAddrNonPIC(N, SDLoc(N), Ty, DAG);
   }
 
-  return getAddrLocal(N, Ty, DAG,
+  return getAddrLocal(N, SDLoc(N), Ty, DAG,
                       Subtarget.isABI_N32() || Subtarget.isABI_N64());
 }
 
 SDValue MipsTargetLowering::lowerVASTART(SDValue Op, SelectionDAG &DAG) const {
   MachineFunction &MF = DAG.getMachineFunction();
   MipsFunctionInfo *FuncInfo = MF.getInfo<MipsFunctionInfo>();
 
   SDLoc DL(Op);
MipsTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   EVT Ty = Callee.getValueType();
 
   if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode>(Callee)) {
     if (IsPICCall) {
       const GlobalValue *Val = G->getGlobal();
       InternalLinkage = Val->hasInternalLinkage();
 
       if (InternalLinkage)
-        Callee = getAddrLocal(G, Ty, DAG,
+        Callee = getAddrLocal(G, DL, Ty, DAG,
                               Subtarget.isABI_N32() || Subtarget.isABI_N64());
       else if (LargeGOT) {
-        Callee = getAddrGlobalLargeGOT(G, Ty, DAG, MipsII::MO_CALL_HI16,
+        Callee = getAddrGlobalLargeGOT(G, DL, Ty, DAG, MipsII::MO_CALL_HI16,
                                        MipsII::MO_CALL_LO16, Chain,
                                        FuncInfo->callPtrInfo(Val));
         IsCallReloc = true;
       } else {
-        Callee = getAddrGlobal(G, Ty, DAG, MipsII::MO_GOT_CALL, Chain,
+        Callee = getAddrGlobal(G, DL, Ty, DAG, MipsII::MO_GOT_CALL, Chain,
                                FuncInfo->callPtrInfo(Val));
         IsCallReloc = true;
       }
     } else
       Callee = DAG.getTargetGlobalAddress(G->getGlobal(), DL, getPointerTy(), 0,
                                           MipsII::MO_NO_FLAG);
     GlobalOrExternal = true;
   }
   else if (ExternalSymbolSDNode *S = dyn_cast<ExternalSymbolSDNode>(Callee)) {
     const char *Sym = S->getSymbol();
 
     if (!Subtarget.isABI_N64() && !IsPIC) // !N64 && static
-      Callee = DAG.getTargetExternalSymbol(Sym, getPointerTy(),
-                                            MipsII::MO_NO_FLAG);
+      Callee =
+          DAG.getTargetExternalSymbol(Sym, getPointerTy(), MipsII::MO_NO_FLAG);
     else if (LargeGOT) {
-      Callee = getAddrGlobalLargeGOT(S, Ty, DAG, MipsII::MO_CALL_HI16,
+      Callee = getAddrGlobalLargeGOT(S, DL, Ty, DAG, MipsII::MO_CALL_HI16,
                                      MipsII::MO_CALL_LO16, Chain,
                                      FuncInfo->callPtrInfo(Sym));
       IsCallReloc = true;
     } else { // N64 || PIC
-      Callee = getAddrGlobal(S, Ty, DAG, MipsII::MO_GOT_CALL, Chain,
+      Callee = getAddrGlobal(S, DL, Ty, DAG, MipsII::MO_GOT_CALL, Chain,
                              FuncInfo->callPtrInfo(Sym));
       IsCallReloc = true;
     }
 
     GlobalOrExternal = true;
   }
 
   SmallVector<SDValue, 8> Ops(1, Chain);

test/DebugInfo/Mips/fn-call-line.ll

+; RUN: llc -mtriple=mips-linux-gnu -filetype=asm -asm-verbose=0 -O0 < %s | FileCheck %s
+; RUN: llc -mtriple=mips-linux-gnu -filetype=obj -O0 < %s | llvm-dwarfdump -debug-dump=line - | FileCheck %s --check-prefix=INT
+
+; Mips used to generate 'jumpy' debug line info around calls. The address
+; calculation for each call to f1() would share the same line info so it would
+; emit output of the form:
+;   .loc $first_call_location
+;   .. address calculation ..
+;   .. function call ..
+;   .. address calculation ..
+;   .loc $second_call_location
+;   .. function call ..
+;   .loc $first_call_location
+;   .. address calculation ..
+;   .loc $third_call_location
+;   .. function call ..
+;   ...
+; which would cause confusing stepping behaviour for the end user.
+;
+; This test checks that we emit more user friendly debug line info of the form:
+;   .loc $first_call_location
+;   .. address calculation ..
+;   .. function call ..
+;   .loc $second_call_location
+;   .. address calculation ..
+;   .. function call ..
+;   .loc $third_call_location
+;   .. address calculation ..
+;   .. function call ..
+;   ...
+;
+; Generated with clang from fn-call-line.c:
+; void f1();
+; void f2() {
+;   f1();
+;   f1();
+; }
+
+; CHECK: .loc 1 2 0{{$}}
+; CHECK-NOT: .loc{{ }}
+; CHECK: .loc 1 3 3 prologue_end{{$}}
+; CHECK-NOT: .loc
+; CHECK: .loc 1 4 3
+
+; INT: {{^}}Address
+; INT: -----
+; INT-NEXT: 2 0 1 0 0 is_stmt{{$}}
+; INT-NEXT: 3 3 1 0 0 is_stmt prologue_end{{$}}
+; INT-NEXT: 4 3 1 0 0 is_stmt{{$}}
+
+
+; Function Attrs: nounwind uwtable
+define void @f2() #0 {
+entry:
+  call void (...)* @f1(), !dbg !11
+  call void (...)* @f1(), !dbg !12
+  ret void, !dbg !13
+}
+
+declare void @f1(...) #1
+
+attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!8, !9}
+!llvm.ident = !{!10}
+
+!0 = !{!"0x11\0012\00clang version 3.7.0 (trunk 226641)\000\00\000\00\001", !1, !2, !2, !3, !2, !2} ; [ DW_TAG_compile_unit ] [/tmp/dbginfo/fn-call-line.c] [DW_LANG_C99]
+!1 = !{!"fn-call-line.c", !"/tmp/dbginfo"}
+!2 = !{}
+!3 = !{!4}
+!4 = !{!"0x2e\00f2\00f2\00\002\000\001\000\000\000\000\002", !1, !5, !6, null, void ()* @f2, null, null, !2} ; [ DW_TAG_subprogram ] [line 2] [def] [f2]
+!5 = !{!"0x29", !1}                               ; [ DW_TAG_file_type ] [/tmp/dbginfo/fn-call-line.c]
+!6 = !{!"0x15\00\000\000\000\000\000\000", null, null, null, !7, null, null, null} ; [ DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
+!7 = !{null}
+!8 = !{i32 2, !"Dwarf Version", i32 4}
+!9 = !{i32 2, !"Debug Info Version", i32 2}
+!10 = !{!"clang version 3.7.0 (trunk 226641)"}
+!11 = !MDLocation(line: 3, column: 3, scope: !4)
+!12 = !MDLocation(line: 4, column: 3, scope: !4)
+!13 = !MDLocation(line: 5, column: 1, scope: !4)