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[SelectionDAG] Salvage debug info for non-constant ADDs #68981

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Merged
merged 3 commits into from
Oct 25, 2023
Merged

[SelectionDAG] Salvage debug info for non-constant ADDs #68981

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06c471a
[DebugInfo] Precommit testcase for pointer addition with unknown offset
dstenb Oct 13, 2023
55ab6cc
[SelectionDAG] Salvage debug info for non-constant ADDs
dstenb Oct 13, 2023
56a02a4
Fix clang-format issue in previous commit (NFC)
dstenb Oct 19, 2023
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43 changes: 33 additions & 10 deletions llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@
#include "llvm/Analysis/MemoryLocation.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Analysis/VectorUtils.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/FunctionLoweringInfo.h"
#include "llvm/CodeGen/ISDOpcodes.h"
Expand Down Expand Up @@ -10781,8 +10782,11 @@ void SelectionDAG::salvageDebugInfo(SDNode &N) {
case ISD::ADD: {
SDValue N0 = N.getOperand(0);
SDValue N1 = N.getOperand(1);
if (!isa<ConstantSDNode>(N0) && isa<ConstantSDNode>(N1)) {
uint64_t Offset = N.getConstantOperandVal(1);
if (!isa<ConstantSDNode>(N0)) {
bool RHSConstant = isa<ConstantSDNode>(N1);
uint64_t Offset;
if (RHSConstant)
Offset = N.getConstantOperandVal(1);

// Rewrite an ADD constant node into a DIExpression. Since we are
// performing arithmetic to compute the variable's *value* in the
Expand All @@ -10791,27 +10795,46 @@ void SelectionDAG::salvageDebugInfo(SDNode &N) {
auto *DIExpr = DV->getExpression();
auto NewLocOps = DV->copyLocationOps();
bool Changed = false;
for (size_t i = 0; i < NewLocOps.size(); ++i) {
size_t OrigLocOpsSize = NewLocOps.size();
for (size_t i = 0; i < OrigLocOpsSize; ++i) {
// We're not given a ResNo to compare against because the whole
// node is going away. We know that any ISD::ADD only has one
// result, so we can assume any node match is using the result.
if (NewLocOps[i].getKind() != SDDbgOperand::SDNODE ||
NewLocOps[i].getSDNode() != &N)
continue;
NewLocOps[i] = SDDbgOperand::fromNode(N0.getNode(), N0.getResNo());
SmallVector<uint64_t, 3> ExprOps;
DIExpression::appendOffset(ExprOps, Offset);
DIExpr = DIExpression::appendOpsToArg(DIExpr, ExprOps, i, true);
if (RHSConstant) {
SmallVector<uint64_t, 3> ExprOps;
DIExpression::appendOffset(ExprOps, Offset);
DIExpr = DIExpression::appendOpsToArg(DIExpr, ExprOps, i, true);
} else {
// Convert to a variadic expression (if not already).
// convertToVariadicExpression() returns a const pointer, so we use
// a temporary const variable here.
const auto *TmpDIExpr =
DIExpression::convertToVariadicExpression(DIExpr);
SmallVector<uint64_t, 3> ExprOps;
ExprOps.push_back(dwarf::DW_OP_LLVM_arg);
ExprOps.push_back(NewLocOps.size());
ExprOps.push_back(dwarf::DW_OP_plus);
SDDbgOperand RHS =
SDDbgOperand::fromNode(N1.getNode(), N1.getResNo());
NewLocOps.push_back(RHS);
DIExpr = DIExpression::appendOpsToArg(TmpDIExpr, ExprOps, i, true);
}
Changed = true;
}
(void)Changed;
assert(Changed && "Salvage target doesn't use N");

bool IsVariadic =
DV->isVariadic() || OrigLocOpsSize != NewLocOps.size();
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@KanRobert KanRobert Nov 17, 2023 •
edited
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We changed the value of IsVariadic here and getDbgValueList(line 10835) would call constructor of SDDbgValue
https://github.com/llvm/llvm-project/blob/main/llvm/lib/CodeGen/SelectionDAG/SDNodeDbgValue.h#L166

it seems the assertion assert(!(IsVariadic && IsIndirect)); in the constructor may fail. In fact, I did see such an error for x86 target.

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#72630


auto AdditionalDependencies = DV->getAdditionalDependencies();
SDDbgValue *Clone = getDbgValueList(DV->getVariable(), DIExpr,
NewLocOps, AdditionalDependencies,
DV->isIndirect(), DV->getDebugLoc(),
DV->getOrder(), DV->isVariadic());
SDDbgValue *Clone = getDbgValueList(
DV->getVariable(), DIExpr, NewLocOps, AdditionalDependencies,
DV->isIndirect(), DV->getDebugLoc(), DV->getOrder(), IsVariadic);
ClonedDVs.push_back(Clone);
DV->setIsInvalidated();
DV->setIsEmitted();
Expand Down
60 changes: 60 additions & 0 deletions llvm/test/DebugInfo/Sparc/pointer-add-unknown-offset-debug-info.mir
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Original file line number Diff line number Diff line change
@@ -0,0 +1,60 @@
# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 3
# RUN: llc -mtriple=sparcv9 %s -start-before=sparc-isel -o - -stop-after=sparc-isel | FileCheck %s
--- |
target datalayout = "E-m:e-i64:64-n32:64-S128"
target triple = "sparcv9"

define void @pointer_add_unknown_offset(ptr %base, i32 %offset) !dbg !7 {
entry:
%idx.ext = sext i32 %offset to i64
%add.ptr = getelementptr inbounds i32, ptr %base, i64 %idx.ext
call void @llvm.dbg.value(metadata ptr %add.ptr, metadata !13, metadata !DIExpression()), !dbg !16
call void @llvm.dbg.value(metadata ptr %add.ptr, metadata !14, metadata !DIExpression(DW_OP_plus_uconst, 3, DW_OP_stack_value)), !dbg !16
call void @llvm.dbg.value(metadata !DIArgList(ptr %add.ptr, ptr %add.ptr), metadata !15, metadata !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_plus)), !dbg !16
store i32 42, ptr %add.ptr, align 4
ret void
}

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

!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!2, !3, !4, !5}
!llvm.ident = !{!6}

!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "test.c", directory: "/tmp", checksumkind: CSK_MD5, checksum: "4321633e52cefeee6e307c697a82574f")
!2 = !{i32 7, !"Dwarf Version", i32 5}
!3 = !{i32 2, !"Debug Info Version", i32 3}
!4 = !{i32 1, !"wchar_size", i32 4}
!5 = !{i32 7, !"debug-info-assignment-tracking", i1 true}
!6 = !{!"clang"}
!7 = distinct !DISubprogram(name: "pointer_add_unknown_offset", scope: !1, file: !1, line: 1, type: !8, scopeLine: 1, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !12)
!8 = !DISubroutineType(types: !9)
!9 = !{null, !10, !11}
!10 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !11, size: 64)
!11 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!12 = !{!13, !14, !15}
!13 = !DILocalVariable(name: "p", scope: !7, file: !1, line: 2, type: !10)
!14 = !DILocalVariable(name: "q", scope: !7, file: !1, line: 2, type: !10)
!15 = !DILocalVariable(name: "r", scope: !7, file: !1, line: 2, type: !10)
!16 = !DILocation(line: 0, scope: !7)
...
---
name: pointer_add_unknown_offset
alignment: 4
tracksRegLiveness: true
body: |
; CHECK-LABEL: name: pointer_add_unknown_offset
; CHECK: bb.0.entry:
; CHECK-NEXT: liveins: $i0, $i1
; CHECK-NEXT: {{ $}}
; CHECK-NEXT: [[COPY:%[0-9]+]]:i64regs = COPY $i1
; CHECK-NEXT: [[COPY1:%[0-9]+]]:i64regs = COPY $i0
; CHECK-NEXT: [[SRAri:%[0-9]+]]:i64regs = SRAri [[COPY]], 0
; CHECK-NEXT: [[SLLXri:%[0-9]+]]:i64regs = SLLXri killed [[SRAri]], 2
; CHECK-NEXT: DBG_VALUE_LIST !13, !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_plus, DW_OP_stack_value), [[COPY1]], [[SLLXri]], debug-location !16
; CHECK-NEXT: DBG_VALUE_LIST !14, !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_plus, DW_OP_plus_uconst, 3, DW_OP_stack_value), [[COPY1]], [[SLLXri]], debug-location !16
; CHECK-NEXT: DBG_VALUE_LIST !15, !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 2, DW_OP_plus, DW_OP_LLVM_arg, 1, DW_OP_LLVM_arg, 3, DW_OP_plus, DW_OP_plus, DW_OP_stack_value), [[COPY1]], [[COPY1]], [[SLLXri]], [[SLLXri]], debug-location !16
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Is this testing the non-variadic case, too?

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Yes, the debug values for "p" and "q" are still non-variadic when entering SelectionDAG::salvageDebugInfo():

 DbgVal(Order=3)(SDNODE=t9:0):"p"
 DbgVal(Order=3)(SDNODE=t9:0):"q"!DIExpression(DW_OP_plus_uconst, 3, DW_OP_stack_value)

; CHECK-NEXT: [[ORri:%[0-9]+]]:intregs = ORri $g0, 42
; CHECK-NEXT: STrr [[COPY1]], killed [[SLLXri]], killed [[ORri]] :: (store (s32) into %ir.add.ptr)
; CHECK-NEXT: RETL 8