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[BPF] Fix a bug for __builtin_preserve_field_info() processing 

Andrii discovered a problem where a simple case similar to below
will generate wrong relocation kind:
  enum { FIELD_EXISTENCE = 2, };
  struct s1 { int a1; };
  int test() {
    struct s1 *v = 0;
    return __builtin_preserve_field_info(v[0], FIELD_EXISTENCE);
  }
The expected relocation kind should be FIELD_EXISTENCE, but
recorded reloc kind in the final object file is FIELD_BYTE_OFFSET,
which is incorrect.

This exposed a bug in generating access strings from intrinsics.
The current access string generation has two steps:
  step 1: find the base struct/union type,
  step 2: traverse members in the base type.

The current implementation relies on at lease one member access
in step 2 to get the correct relocation kind, which is true
in typical cases. But if there is no member accesses, the current
implementation falls to the default info kind FIELD_BYTE_OFFSET.
This is incorrect, we should still record the reloc kind
based on the user input. This patch fixed this issue by properly
recording the reloc kind in such cases.

Differential Revision: https://reviews.llvm.org/D82932
This commit is contained in:
Yonghong Song 2020-06-30 15:27:24 -07:00
parent f5e0ae240f
commit 7f6bc84a97
2 changed files with 85 additions and 1 deletions
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4
llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
View File

@ -808,8 +808,10 @@ Value *BPFAbstractMemberAccess::computeBaseAndAccessKey(CallInst *Call,
CInfo = StackElem.second;
CallStack.pop();
if (CInfo.Kind == BPFPreserveFieldInfoAI)
if (CInfo.Kind == BPFPreserveFieldInfoAI) {
InfoKind = CInfo.AccessIndex;
break;
}
// If the next Call (the top of the stack) is a BPFPreserveFieldInfoAI,
// the action will be extracting field info.

82
llvm/test/CodeGen/BPF/CORE/intrinsic-array-2.ll Normal file
View File

@ -0,0 +1,82 @@
; RUN: llc -march=bpfel -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK,CHECK-ALU64 %s
; RUN: llc -march=bpfeb -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK,CHECK-ALU64 %s
; RUN: llc -march=bpfel -mattr=+alu32 -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK,CHECK-ALU32 %s
; RUN: llc -march=bpfeb -mattr=+alu32 -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK,CHECK-ALU32 %s
; Source:
; enum { FIELD_EXISTENCE = 2, };
; struct s1 { int a1; };
; int test() {
; struct s1 *v = 0;
; return __builtin_preserve_field_info(v[0], FIELD_EXISTENCE);
; }
; Compilation flag:
; clang -target bpf -O2 -g -S -emit-llvm test.c
%struct.s1 = type { i32 }
; Function Attrs: nounwind readnone
define dso_local i32 @test() local_unnamed_addr #0 !dbg !17 {
entry:
call void @llvm.dbg.value(metadata %struct.s1* null, metadata !21, metadata !DIExpression()), !dbg !22
%0 = tail call %struct.s1* @llvm.preserve.array.access.index.p0s_struct.s1s.p0s_struct.s1s(%struct.s1* null, i32 0, i32 0), !dbg !23, !llvm.preserve.access.index !8
%1 = tail call i32 @llvm.bpf.preserve.field.info.p0s_struct.s1s(%struct.s1* %0, i64 2), !dbg !24
ret i32 %1, !dbg !25
}
; CHECK: .long 16 # BTF_KIND_STRUCT(id = 4)
; CHECK: .ascii ".text" # string offset=10
; CHECK: .ascii "s1" # string offset=16
; CHECK: .byte 48 # string offset=22
; CHECK: .long 16 # FieldReloc
; CHECK-NEXT: .long 10 # Field reloc section string offset=10
; CHECK-NEXT: .long 1
; CHECK-NEXT: .long .Ltmp{{[0-9]+}}
; CHECK-NEXT: .long 4
; CHECK-NEXT: .long 22
; CHECK-NEXT: .long 2
; Function Attrs: nounwind readnone
declare %struct.s1* @llvm.preserve.array.access.index.p0s_struct.s1s.p0s_struct.s1s(%struct.s1*, i32 immarg, i32 immarg) #1
; Function Attrs: nounwind readnone
declare i32 @llvm.bpf.preserve.field.info.p0s_struct.s1s(%struct.s1*, i64 immarg) #1
; Function Attrs: nounwind readnone speculatable willreturn
declare void @llvm.dbg.value(metadata, metadata, metadata) #2
attributes #0 = { nounwind readnone "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { nounwind readnone }
attributes #2 = { nounwind readnone speculatable willreturn }
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!13, !14, !15}
!llvm.ident = !{!16}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 11.0.0 (https://github.com/llvm/llvm-project.git 32791937d7aceb0a5e1eaabf1bb1a6dbe1639792)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !7, splitDebugInlining: false, nameTableKind: None)
!1 = !DIFile(filename: "test.c", directory: "/tmp/home/yhs/work/tests/core")
!2 = !{!3}
!3 = !DICompositeType(tag: DW_TAG_enumeration_type, file: !1, line: 1, baseType: !4, size: 32, elements: !5)
!4 = !DIBasicType(name: "unsigned int", size: 32, encoding: DW_ATE_unsigned)
!5 = !{!6}
!6 = !DIEnumerator(name: "FIELD_EXISTENCE", value: 2, isUnsigned: true)
!7 = !{!8}
!8 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 64)
!9 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "s1", file: !1, line: 2, size: 32, elements: !10)
!10 = !{!11}
!11 = !DIDerivedType(tag: DW_TAG_member, name: "a1", scope: !9, file: !1, line: 2, baseType: !12, size: 32)
!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!13 = !{i32 7, !"Dwarf Version", i32 4}
!14 = !{i32 2, !"Debug Info Version", i32 3}
!15 = !{i32 1, !"wchar_size", i32 4}
!16 = !{!"clang version 11.0.0 (https://github.com/llvm/llvm-project.git 32791937d7aceb0a5e1eaabf1bb1a6dbe1639792)"}
!17 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 3, type: !18, scopeLine: 3, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !20)
!18 = !DISubroutineType(types: !19)
!19 = !{!12}
!20 = !{!21}
!21 = !DILocalVariable(name: "v", scope: !17, file: !1, line: 4, type: !8)
!22 = !DILocation(line: 0, scope: !17)
!23 = !DILocation(line: 5, column: 40, scope: !17)
!24 = !DILocation(line: 5, column: 10, scope: !17)
!25 = !DILocation(line: 5, column: 3, scope: !17)