Commit 0368b422 authored by Vedant Kumar's avatar Vedant Kumar
Browse files

[entry values] ARM: Add a describeLoadedValue override (PR45025) 

As a narrow stopgap for the assertion failure described in PR45025, add
a describeLoadedValue override to ARMBaseInstrInfo and use it to detect
copies in which the forwarding reg is a super/sub reg of the copy
destination. For the moment this is unsupported.

Several follow ups are possible:

1) Handle VORRq. At the moment, we do not, because isCopyInstrImpl
   returns early when !MI.isMoveReg().

2) In the case where forwarding reg is a super-reg of the copy
   destination, we should be able to describe the forwarding reg as a
   subreg within the copy destination. I'm not 100% sure about this, but
   it looks like that's what's done in AArch64InstrInfo.

3) In the case where the forwarding reg is a sub-reg of the copy
   destination, maybe we could describe the forwarding reg using the
   copy destinaion and a DW_OP_LLVM_fragment (I guess this should be
   possible after D75036).

https://bugs.llvm.org/show_bug.cgi?id=45025
rdar://59772698

Differential Revision: https://reviews.llvm.org/D75273
parent 52f889ab

llvm/lib/CodeGen/TargetInstrInfo.cpp

+5 −0
Original line number Diff line number Diff line
@@ -1150,6 +1150,11 @@ TargetInstrInfo::describeLoadedValue(const MachineInstr &MI, 
  if (auto DestSrc = isCopyInstr(MI)) {

    Register DestReg = DestSrc->Destination->getReg();



    // If the copy destination is the forwarding reg, describe the forwarding

    // reg using the copy source as the backup location. Example:

    //

    //   x0 = MOV x7

    //   call callee(x0)      ; x0 described as x7

    if (Reg == DestReg)

      return ParamLoadedValue(*DestSrc->Source, Expr);

llvm/lib/Target/ARM/ARMBaseInstrInfo.cpp

+30 −0
Original line number Diff line number Diff line
@@ -1027,6 +1027,36 @@ ARMBaseInstrInfo::isCopyInstrImpl(const MachineInstr &MI) const { 
  return DestSourcePair{MI.getOperand(0), MI.getOperand(1)};

}



Optional<ParamLoadedValue>

ARMBaseInstrInfo::describeLoadedValue(const MachineInstr &MI,

                                      Register Reg) const {

  if (auto DstSrcPair = isCopyInstrImpl(MI)) {

    Register DstReg = DstSrcPair->Destination->getReg();



    // TODO: We don't handle cases where the forwarding reg is narrower/wider

    // than the copy registers. Consider for example:

    //

    //   s16 = VMOVS s0

    //   s17 = VMOVS s1

    //   call @callee(d0)

    //

    // We'd like to describe the call site value of d0 as d8, but this requires

    // gathering and merging the descriptions for the two VMOVS instructions.

    //

    // We also don't handle the reverse situation, where the forwarding reg is

    // narrower than the copy destination:

    //

    //   d8 = VMOVD d0

    //   call @callee(s1)

    //

    // We need to produce a fragment description (the call site value of s1 is

    // /not/ just d8).

    if (DstReg != Reg)

      return None;

  }

  return TargetInstrInfo::describeLoadedValue(MI, Reg);

}



const MachineInstrBuilder &

ARMBaseInstrInfo::AddDReg(MachineInstrBuilder &MIB, unsigned Reg,

                          unsigned SubIdx, unsigned State,

llvm/lib/Target/ARM/ARMBaseInstrInfo.h

+5 −0
Original line number Diff line number Diff line
@@ -105,6 +105,11 @@ protected: 
  Optional<DestSourcePair>

  isCopyInstrImpl(const MachineInstr &MI) const override;



  /// Specialization of \ref TargetInstrInfo::describeLoadedValue, used to

  /// enhance debug entry value descriptions for ARM targets.

  Optional<ParamLoadedValue> describeLoadedValue(const MachineInstr &MI,

                                                 Register Reg) const override;



public:

  // Return whether the target has an explicit NOP encoding.

  bool hasNOP() const;

llvm/test/DebugInfo/MIR/ARM/call-site-info-vmovd.mir

0 → 100644
+102 −0
Original line number Diff line number Diff line 
# RUN: llc -O1 -debug-entry-values -filetype=obj -mtriple thumbv7em-apple-unknown-macho -start-after=machineverifier %s -o %t.o

# RUN: llvm-dwarfdump %t.o | FileCheck %s



# Crash test, reduced from:

#

# a(float);

# b(double c) {

#   d();

#   a(c);

# }

#

# Some minor surgery was performed on the MIR to remove a call to a truncating

# cast builtin between the calls to "d" and "a", and to force d0 as the copy dst

# and s0 as the forwarding reg.

#

# This was done to test the case where the copy dst (d0) is a super-reg of the

# forwarding reg (s0).



# CHECK: DW_TAG_GNU_call_site

# CHECK-NEXT: DW_AT_abstract_origin {{.*}} "a"

# CHECK-NOT: call_site_parameter



--- |

  target datalayout = "e-m:o-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"

  target triple = "thumbv7em-apple-unknown-macho"

  ; Function Attrs: nounwind optsize uwtable

  define arm_aapcs_vfpcc i32 @b(double %c) local_unnamed_addr #0 !dbg !16 {

  entry:

    call void @llvm.dbg.value(metadata double %c, metadata !21, metadata !DIExpression()), !dbg !22

    %call = tail call arm_aapcs_vfpcc i32 bitcast (i32 (...)* @d to i32 ()*)(), !dbg !23

    %conv = fptrunc double %c to float, !dbg !24

    %call1 = tail call arm_aapcs_vfpcc i32 @a(float %conv), !dbg !25

    ret i32 undef, !dbg !26

  }

  declare arm_aapcs_vfpcc i32 @d(...) local_unnamed_addr #0

  declare !dbg !4 arm_aapcs_vfpcc i32 @a(float) local_unnamed_addr #0

  declare void @llvm.dbg.value(metadata, metadata, metadata)

  declare void @llvm.stackprotector(i8*, i8**)



  attributes #0 = { "disable-tail-calls"="false" "frame-pointer"="all" }



  !llvm.dbg.cu = !{!0}

  !llvm.module.flags = !{!10, !11, !12, !13, !14}

  !llvm.ident = !{!15}



  !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 10.0.0 (git@github.com:apple/llvm-project.git 6203ec90d0bb0fd705fc0ad00ee263e5579aa709)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3, nameTableKind: None)

  !1 = !DIFile(filename: "jnyn_freeBSD.c", directory: "/Users/vsk/tmp/jnyn")

  !2 = !{}

  !3 = !{!4}

  !4 = !DISubprogram(name: "a", scope: !5, file: !5, line: 1, type: !6, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !2)

  !5 = !DIFile(filename: "unreduced2.c", directory: "/Users/vsk/tmp/jnyn")

  !6 = !DISubroutineType(types: !7)

  !7 = !{!8, !9}

  !8 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)

  !9 = !DIBasicType(name: "float", size: 32, encoding: DW_ATE_float)

  !10 = !{i32 7, !"Dwarf Version", i32 4}

  !11 = !{i32 2, !"Debug Info Version", i32 3}

  !12 = !{i32 1, !"wchar_size", i32 4}

  !13 = !{i32 1, !"min_enum_size", i32 4}

  !14 = !{i32 7, !"PIC Level", i32 2}

  !15 = !{!"clang version 10.0.0 (git@github.com:apple/llvm-project.git 6203ec90d0bb0fd705fc0ad00ee263e5579aa709)"}

  !16 = distinct !DISubprogram(name: "b", scope: !5, file: !5, line: 2, type: !17, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !20)

  !17 = !DISubroutineType(types: !18)

  !18 = !{!8, !19}

  !19 = !DIBasicType(name: "double", size: 64, encoding: DW_ATE_float)

  !20 = !{!21}

  !21 = !DILocalVariable(name: "c", arg: 1, scope: !16, file: !5, line: 2, type: !19)

  !22 = !DILocation(line: 0, scope: !16)

  !23 = !DILocation(line: 3, column: 3, scope: !16)

  !24 = !DILocation(line: 4, column: 5, scope: !16)

  !25 = !DILocation(line: 4, column: 3, scope: !16)

  !26 = !DILocation(line: 5, column: 1, scope: !16)



...

---

name:            b

callSites:

  - { bb: 0, offset: 12, fwdArgRegs: [] }

  - { bb: 0, offset: 15, fwdArgRegs:

      - { arg: 0, reg: '$s0' } }

body:             |

  bb.0.entry:

    liveins: $d0, $lr, $d8



    DBG_VALUE $d0, $noreg, !21, !DIExpression(), debug-location !22

    frame-setup tPUSH 14, $noreg, $r7, killed $lr, implicit-def $sp, implicit $sp

    frame-setup CFI_INSTRUCTION def_cfa_offset 8

    frame-setup CFI_INSTRUCTION offset $lr, -4

    frame-setup CFI_INSTRUCTION offset $r7, -8

    $r7 = frame-setup tMOVr $sp, 14, $noreg

    frame-setup CFI_INSTRUCTION def_cfa_register $r7

    $sp = frame-setup VSTMDDB_UPD $sp, 14, $noreg, killed $d8

    frame-setup CFI_INSTRUCTION offset $d8, -16

    $s16 = VMOVS killed $s0, 14, $noreg

    $s17 = VMOVS killed $s1, 14, $noreg, implicit-def $d8

    DBG_VALUE $d8, $noreg, !21, !DIExpression(), debug-location !22

    tBL 14, $noreg, @d, csr_aapcs, implicit-def dead $lr, implicit $sp, implicit-def $sp, implicit-def dead $r0, debug-location !23

    $d0 = VMOVD killed $d8, 14, $noreg, debug-location !24

    DBG_VALUE $d0, $noreg, !21, !DIExpression(), debug-location !22

    tTAILJMPd @a, 14, $noreg, implicit $sp, implicit $sp, implicit killed $s0, debug-location !25



...

llvm/test/DebugInfo/MIR/ARM/call-site-info-vmovs.mir

0 → 100644
+95 −0
Original line number Diff line number Diff line 
# RUN: llc -O1 -debug-entry-values -filetype=obj -mtriple thumbv7em-apple-unknown-macho -start-after=machineverifier %s -o %t.o

# RUN: llvm-dwarfdump %t.o | FileCheck %s



# Crash test, reduced from:

#

# a(double);

# b(double c) {

#   d();

#   a(c);

# }



# CHECK: DW_TAG_GNU_call_site

# CHECK-NEXT: DW_AT_abstract_origin {{.*}} "a"

# CHECK-NOT: call_site_parameter



--- |

  ; ModuleID = 'unreduced.c'

  source_filename = "unreduced.c"

  target datalayout = "e-m:o-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"

  target triple = "thumbv7em-apple-unknown-macho"

  ; Function Attrs: nounwind optsize uwtable

  define arm_aapcs_vfpcc i32 @b(double %c) local_unnamed_addr #0 !dbg !16 {

  entry:

    call void @llvm.dbg.value(metadata double %c, metadata !18, metadata !DIExpression()), !dbg !19

    %call = tail call arm_aapcs_vfpcc i32 bitcast (i32 (...)* @d to i32 ()*)(), !dbg !20

    %call1 = tail call arm_aapcs_vfpcc i32 @a(double %c), !dbg !21

    ret i32 undef, !dbg !22

  }

  declare arm_aapcs_vfpcc i32 @d(...) local_unnamed_addr #0

  declare !dbg !4 arm_aapcs_vfpcc i32 @a(double) local_unnamed_addr #0

  declare void @llvm.dbg.value(metadata, metadata, metadata)

  declare void @llvm.stackprotector(i8*, i8**)



  attributes #0 = { "disable-tail-calls"="false" "frame-pointer"="all" }



  !llvm.dbg.cu = !{!0}

  !llvm.module.flags = !{!10, !11, !12, !13, !14}

  !llvm.ident = !{!15}



  !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 10.0.0 (git@github.com:apple/llvm-project.git 6203ec90d0bb0fd705fc0ad00ee263e5579aa709)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3, nameTableKind: None)

  !1 = !DIFile(filename: "jnyn_freeBSD.c", directory: "/Users/vsk/tmp/jnyn")

  !2 = !{}

  !3 = !{!4}

  !4 = !DISubprogram(name: "a", scope: !5, file: !5, line: 1, type: !6, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !2)

  !5 = !DIFile(filename: "unreduced.c", directory: "/Users/vsk/tmp/jnyn")

  !6 = !DISubroutineType(types: !7)

  !7 = !{!8, !9}

  !8 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)

  !9 = !DIBasicType(name: "double", size: 64, encoding: DW_ATE_float)

  !10 = !{i32 7, !"Dwarf Version", i32 4}

  !11 = !{i32 2, !"Debug Info Version", i32 3}

  !12 = !{i32 1, !"wchar_size", i32 4}

  !13 = !{i32 1, !"min_enum_size", i32 4}

  !14 = !{i32 7, !"PIC Level", i32 2}

  !15 = !{!"clang version 10.0.0 (git@github.com:apple/llvm-project.git 6203ec90d0bb0fd705fc0ad00ee263e5579aa709)"}

  !16 = distinct !DISubprogram(name: "b", scope: !5, file: !5, line: 2, type: !6, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !17)

  !17 = !{!18}

  !18 = !DILocalVariable(name: "c", arg: 1, scope: !16, file: !5, line: 2, type: !9)

  !19 = !DILocation(line: 0, scope: !16)

  !20 = !DILocation(line: 3, column: 3, scope: !16)

  !21 = !DILocation(line: 4, column: 3, scope: !16)

  !22 = !DILocation(line: 5, column: 1, scope: !16)



...

---

name:            b

callSites:

  - { bb: 0, offset: 12, fwdArgRegs: [] }

  - { bb: 0, offset: 18, fwdArgRegs:

      - { arg: 0, reg: '$d0' } }

body:             |

  bb.0.entry:

    liveins: $d0, $lr, $d8



    DBG_VALUE $d0, $noreg, !18, !DIExpression(), debug-location !19

    frame-setup tPUSH 14, $noreg, $r7, killed $lr, implicit-def $sp, implicit $sp

    frame-setup CFI_INSTRUCTION def_cfa_offset 8

    frame-setup CFI_INSTRUCTION offset $lr, -4

    frame-setup CFI_INSTRUCTION offset $r7, -8

    $r7 = frame-setup tMOVr $sp, 14, $noreg

    frame-setup CFI_INSTRUCTION def_cfa_register $r7

    $sp = frame-setup VSTMDDB_UPD $sp, 14, $noreg, killed $d8

    frame-setup CFI_INSTRUCTION offset $d8, -16

    $s16 = VMOVS killed $s0, 14, $noreg

    $s17 = VMOVS killed $s1, 14, $noreg, implicit-def $d8

    DBG_VALUE $d8, $noreg, !18, !DIExpression(), debug-location !19

    tBL 14, $noreg, @d, csr_aapcs, implicit-def dead $lr, implicit $sp, implicit-def $sp, implicit-def dead $r0, debug-location !20

    $s0 = VMOVS killed $s16, 14, $noreg, debug-location !21

    $s1 = VMOVS killed $s17, 14, $noreg, implicit-def $d0, debug-location !21

    DBG_VALUE $d0, $noreg, !18, !DIExpression(), debug-location !19

    $sp = VLDMDIA_UPD $sp, 14, $noreg, def $d8, debug-location !21

    $sp = t2LDMIA_UPD $sp, 14, $noreg, def $r7, def $lr, debug-location !21

    tTAILJMPd @a, 14, $noreg, implicit $sp, implicit $sp, implicit killed $d0, debug-location !21



...