[llvm] d96c1bb - [BPF] disable ReduceLoadWidth during SelectionDag phase
Tom Stellard via llvm-commits
llvm-commits at lists.llvm.org
Tue Feb 4 18:47:05 PST 2020
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?
-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://reviews.llvm.org/D73997
>
> 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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