[llvm] d96c1bb - [BPF] disable ReduceLoadWidth during SelectionDag phase
Yonghong Song via llvm-commits
llvm-commits at lists.llvm.org
Tue Feb 4 19:17:07 PST 2020
On 2/4/20 6:47 PM, Tom Stellard wrote:
> On 02/04/2020 06:43 PM, Yonghong Song via llvm-commits wrote:
>>
>> Author: Yonghong Song
>> Date: 2020-02-04T18:37:43-08:00
>> New Revision: d96c1bbaa03574daf759e5e9a6c75047c5e3af64
>>
>> URL: https://github.com/llvm/llvm-project/commit/d96c1bbaa03574daf759e5e9a6c75047c5e3af64
>> DIFF: https://github.com/llvm/llvm-project/commit/d96c1bbaa03574daf759e5e9a6c75047c5e3af64.diff
>>
>
> Is this a candidate to backport to the release/10.x branch?
Yes. I just file a release blocking bug
https://bugs.llvm.org/show_bug.cgi?id=44787.
Thanks!
Yonghong
>
> -Tom
>
>> LOG: [BPF] disable ReduceLoadWidth during SelectionDag phase
>>
>> The compiler may transform the following code
>> ctx = ctx + reloc_offset
>> ... (*(u32 *)ctx) & 0x8000 ...
>> to
>> ctx = ctx + reloc_offset
>> ... (*(u8 *)(ctx + 1)) & 0x80 ...
>> where reloc_offset will be replaced with a constant during
>> AsmPrinter phase.
>>
>> The above transformed code will be rejected the kernel verifier
>> as it does not allow
>> *(type *)((ctx + non_zero_offset1) + non_zero_offset2)
>> style access pattern.
>>
>> It is hard at SelectionDag phase to identify whether a load
>> is related to context or not. Sometime, interprocedure analysis
>> may be needed. So let us simply prevent such optimization
>> from happening.
>>
>> Differential Revision: https://urldefense.proofpoint.com/v2/url?u=https-3A__reviews.llvm.org_D73997&d=DwICaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=nK1p8u9g85_MsIIyLMJfiGid-qarWxlZuSHn_2EYCK8&s=HIhOfyKOoTlzJDm-3SwZIj6OPQU8DGeOUp7jP82soWA&e=
>>
>> Added:
>> llvm/test/CodeGen/BPF/CORE/no-narrow-load.ll
>>
>> Modified:
>> llvm/lib/Target/BPF/BPFISelLowering.h
>>
>> Removed:
>>
>>
>>
>> ################################################################################
>> diff --git a/llvm/lib/Target/BPF/BPFISelLowering.h b/llvm/lib/Target/BPF/BPFISelLowering.h
>> index f7ee971deb82..0e9ec1398aeb 100644
>> --- a/llvm/lib/Target/BPF/BPFISelLowering.h
>> +++ b/llvm/lib/Target/BPF/BPFISelLowering.h
>> @@ -109,6 +109,19 @@ class BPFTargetLowering : public TargetLowering {
>> return true;
>> }
>>
>> + // Prevent reducing load width during SelectionDag phase.
>> + // Otherwise, we may transform the following
>> + // ctx = ctx + reloc_offset
>> + // ... (*(u32 *)ctx) & 0x8000...
>> + // to
>> + // ctx = ctx + reloc_offset
>> + // ... (*(u8 *)(ctx + 1)) & 0x80 ...
>> + // which will be rejected by the verifier.
>> + bool shouldReduceLoadWidth(SDNode *Load, ISD::LoadExtType ExtTy,
>> + EVT NewVT) const override {
>> + return false;
>> + }
>> +
>> unsigned EmitSubregExt(MachineInstr &MI, MachineBasicBlock *BB, unsigned Reg,
>> bool isSigned) const;
>>
>>
>> diff --git a/llvm/test/CodeGen/BPF/CORE/no-narrow-load.ll b/llvm/test/CodeGen/BPF/CORE/no-narrow-load.ll
>> new file mode 100644
>> index 000000000000..fd33f03883c2
>> --- /dev/null
>> +++ b/llvm/test/CodeGen/BPF/CORE/no-narrow-load.ll
>> @@ -0,0 +1,156 @@
>> +; RUN: llc -march=bpfel -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
>> +; RUN: llc -march=bpfeb -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
>> +; Source code:
>> +; struct data_t {
>> +; int d1;
>> +; int d2;
>> +; };
>> +; struct info_t {
>> +; int pid;
>> +; int flags;
>> +; } __attribute__((preserve_access_index));
>> +;
>> +; extern void output(void *);
>> +; void test(struct info_t * args) {
>> +; int is_mask2 = args->flags & 0x10000;
>> +; struct data_t data = {};
>> +;
>> +; data.d1 = is_mask2 ? 2 : args->pid;
>> +; data.d2 = (is_mask2 || (args->flags & 0x8000)) ? 1 : 2;
>> +; output(&data);
>> +; }
>> +; Compilation flag:
>> +; clang -target bpf -O2 -g -S -emit-llvm test.c
>> +
>> +%struct.info_t = type { i32, i32 }
>> +%struct.data_t = type { i32, i32 }
>> +
>> +; Function Attrs: nounwind
>> +define dso_local void @test(%struct.info_t* readonly %args) local_unnamed_addr #0 !dbg !12 {
>> +entry:
>> + %data = alloca i64, align 8
>> + %tmpcast = bitcast i64* %data to %struct.data_t*
>> + call void @llvm.dbg.value(metadata %struct.info_t* %args, metadata !22, metadata !DIExpression()), !dbg !29
>> + %0 = tail call i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.info_ts(%struct.info_t* %args, i32 1, i32 1), !dbg !30, !llvm.preserve.access.index !16
>> + %1 = load i32, i32* %0, align 4, !dbg !30, !tbaa !31
>> + %and = and i32 %1, 65536, !dbg !36
>> + call void @llvm.dbg.value(metadata i32 %and, metadata !23, metadata !DIExpression()), !dbg !29
>> + %2 = bitcast i64* %data to i8*, !dbg !37
>> + call void @llvm.lifetime.start.p0i8(i64 8, i8* nonnull %2) #5, !dbg !37
>> + call void @llvm.dbg.declare(metadata %struct.data_t* %tmpcast, metadata !24, metadata !DIExpression()), !dbg !38
>> + store i64 0, i64* %data, align 8, !dbg !38
>> + %tobool = icmp eq i32 %and, 0, !dbg !39
>> + br i1 %tobool, label %cond.false, label %lor.end.critedge, !dbg !39
>> +
>> +cond.false: ; preds = %entry
>> + %3 = tail call i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.info_ts(%struct.info_t* %args, i32 0, i32 0), !dbg !40, !llvm.preserve.access.index !16
>> + %4 = load i32, i32* %3, align 4, !dbg !40, !tbaa !41
>> + %d1 = bitcast i64* %data to i32*, !dbg !42
>> + store i32 %4, i32* %d1, align 8, !dbg !43, !tbaa !44
>> + %5 = load i32, i32* %0, align 4, !dbg !46, !tbaa !31
>> + %and2 = and i32 %5, 32768, !dbg !47
>> + %tobool3 = icmp eq i32 %and2, 0, !dbg !48
>> + %phitmp = select i1 %tobool3, i32 2, i32 1, !dbg !48
>> + br label %lor.end, !dbg !48
>> +
>> +lor.end.critedge: ; preds = %entry
>> + %d1.c = bitcast i64* %data to i32*, !dbg !42
>> + store i32 2, i32* %d1.c, align 8, !dbg !43, !tbaa !44
>> + br label %lor.end, !dbg !48
>> +
>> +lor.end: ; preds = %lor.end.critedge, %cond.false
>> + %6 = phi i32 [ %phitmp, %cond.false ], [ 1, %lor.end.critedge ]
>> + %d2 = getelementptr inbounds %struct.data_t, %struct.data_t* %tmpcast, i64 0, i32 1, !dbg !49
>> + store i32 %6, i32* %d2, align 4, !dbg !50, !tbaa !51
>> + call void @output(i8* nonnull %2) #5, !dbg !52
>> + call void @llvm.lifetime.end.p0i8(i64 8, i8* nonnull %2) #5, !dbg !53
>> + ret void, !dbg !53
>> +}
>> +
>> +; CHECK: r[[LOAD1:[0-9]+]] = *(u32 *)(r{{[0-9]+}} + 4)
>> +; CHECK: r[[LOAD1]] &= 65536
>> +; CHECK: r[[LOAD2:[0-9]+]] = *(u32 *)(r{{[0-9]+}} + 4)
>> +; CHECK: r[[LOAD2]] &= 32768
>> +
>> +; Function Attrs: nounwind readnone speculatable willreturn
>> +declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
>> +
>> +; Function Attrs: argmemonly nounwind willreturn
>> +declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture) #2
>> +
>> +; Function Attrs: nounwind readnone
>> +declare i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.info_ts(%struct.info_t*, i32 immarg, i32 immarg) #3
>> +
>> +declare !dbg !4 dso_local void @output(i8*) local_unnamed_addr #4
>> +
>> +; Function Attrs: argmemonly nounwind willreturn
>> +declare void @llvm.lifetime.end.p0i8(i64 immarg, i8* nocapture) #2
>> +
>> +; Function Attrs: nounwind readnone speculatable willreturn
>> +declare void @llvm.dbg.value(metadata, metadata, metadata) #1
>> +
>> +attributes #0 = { nounwind "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"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
>> +attributes #1 = { nounwind readnone speculatable willreturn }
>> +attributes #2 = { argmemonly nounwind willreturn }
>> +attributes #3 = { nounwind readnone }
>> +attributes #4 = { "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="all" "less-precise-fpmad"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
>> +attributes #5 = { nounwind }
>> +
>> +!llvm.dbg.cu = !{!0}
>> +!llvm.module.flags = !{!8, !9, !10}
>> +!llvm.ident = !{!11}
>> +
>> +!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 11.0.0 (https://github.com/llvm/llvm-project.git 5884aae58f56786475bbc0f13ad8bd35f7f1ce69)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !3, splitDebugInlining: false, nameTableKind: None)
>> +!1 = !DIFile(filename: "test.c", directory: "/tmp/home/yhs/work/tests/core")
>> +!2 = !{}
>> +!3 = !{!4}
>> +!4 = !DISubprogram(name: "output", scope: !1, file: !1, line: 10, type: !5, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !2)
>> +!5 = !DISubroutineType(types: !6)
>> +!6 = !{null, !7}
>> +!7 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
>> +!8 = !{i32 7, !"Dwarf Version", i32 4}
>> +!9 = !{i32 2, !"Debug Info Version", i32 3}
>> +!10 = !{i32 1, !"wchar_size", i32 4}
>> +!11 = !{!"clang version 11.0.0 (https://github.com/llvm/llvm-project.git 5884aae58f56786475bbc0f13ad8bd35f7f1ce69)"}
>> +!12 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 11, type: !13, scopeLine: 11, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !21)
>> +!13 = !DISubroutineType(types: !14)
>> +!14 = !{null, !15}
>> +!15 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !16, size: 64)
>> +!16 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "info_t", file: !1, line: 5, size: 64, elements: !17)
>> +!17 = !{!18, !20}
>> +!18 = !DIDerivedType(tag: DW_TAG_member, name: "pid", scope: !16, file: !1, line: 6, baseType: !19, size: 32)
>> +!19 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
>> +!20 = !DIDerivedType(tag: DW_TAG_member, name: "flags", scope: !16, file: !1, line: 7, baseType: !19, size: 32, offset: 32)
>> +!21 = !{!22, !23, !24}
>> +!22 = !DILocalVariable(name: "args", arg: 1, scope: !12, file: !1, line: 11, type: !15)
>> +!23 = !DILocalVariable(name: "is_mask2", scope: !12, file: !1, line: 12, type: !19)
>> +!24 = !DILocalVariable(name: "data", scope: !12, file: !1, line: 13, type: !25)
>> +!25 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "data_t", file: !1, line: 1, size: 64, elements: !26)
>> +!26 = !{!27, !28}
>> +!27 = !DIDerivedType(tag: DW_TAG_member, name: "d1", scope: !25, file: !1, line: 2, baseType: !19, size: 32)
>> +!28 = !DIDerivedType(tag: DW_TAG_member, name: "d2", scope: !25, file: !1, line: 3, baseType: !19, size: 32, offset: 32)
>> +!29 = !DILocation(line: 0, scope: !12)
>> +!30 = !DILocation(line: 12, column: 24, scope: !12)
>> +!31 = !{!32, !33, i64 4}
>> +!32 = !{!"info_t", !33, i64 0, !33, i64 4}
>> +!33 = !{!"int", !34, i64 0}
>> +!34 = !{!"omnipotent char", !35, i64 0}
>> +!35 = !{!"Simple C/C++ TBAA"}
>> +!36 = !DILocation(line: 12, column: 30, scope: !12)
>> +!37 = !DILocation(line: 13, column: 3, scope: !12)
>> +!38 = !DILocation(line: 13, column: 17, scope: !12)
>> +!39 = !DILocation(line: 15, column: 13, scope: !12)
>> +!40 = !DILocation(line: 15, column: 34, scope: !12)
>> +!41 = !{!32, !33, i64 0}
>> +!42 = !DILocation(line: 15, column: 8, scope: !12)
>> +!43 = !DILocation(line: 15, column: 11, scope: !12)
>> +!44 = !{!45, !33, i64 0}
>> +!45 = !{!"data_t", !33, i64 0, !33, i64 4}
>> +!46 = !DILocation(line: 16, column: 33, scope: !12)
>> +!47 = !DILocation(line: 16, column: 39, scope: !12)
>> +!48 = !DILocation(line: 16, column: 23, scope: !12)
>> +!49 = !DILocation(line: 16, column: 8, scope: !12)
>> +!50 = !DILocation(line: 16, column: 11, scope: !12)
>> +!51 = !{!45, !33, i64 4}
>> +!52 = !DILocation(line: 17, column: 3, scope: !12)
>> +!53 = !DILocation(line: 18, column: 1, scope: !12)
>>
>>
>>
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