BPF: fix a CORE optimization bug

For the test case in this patch like below
  struct t { int a; } __attribute__((preserve_access_index));
  int foo(void *);
  int test(struct t *arg) {
      long param[1];
      param[0] = (long)&arg->a;
      return foo(param);
  }

The IR right before BPF SimplifyPatchable phase:
  %1:gpr = LD_imm64 @"llvm.t:0:0$0:0"
  %2:gpr = LDD killed %1:gpr, 0
  %3:gpr = ADD_rr %0:gpr(tied-def 0), killed %2:gpr
  STD killed %3:gpr, %stack.0.param, 0
After SimplifyPatchable phase, the incorrect IR is generated:
  %1:gpr = LD_imm64 @"llvm.t:0:0$0:0"
  %3:gpr = ADD_rr %0:gpr(tied-def 0), killed %1:gpr
  CORE_MEM killed %3:gpr, 306, %0:gpr, @"llvm.t:0:0$0:0"

Note that CORE_MEM pseudo op is introduced to encode
memory operations related to CORE. In the above, we intend
to check whether we have a store like
   *(%3:gpr + 0) = ...
and if this is the case, we could replace it with
   *(%0:gpr + @"llvm.t:0:0$0:0"_ = ...

Unfortunately, in the above, IR for the store is
   *(%stack.0.param + 0) = %3:gpr
and transformation should not happen.

Note that we won't have problem if the actual CORE
dereference (arg->a) happens.

This patch fixed the problem by skip CORE optimization if
the use of ADD_rr result is not the base address of the store
operation.

Differential Revision: https://reviews.llvm.org/D78466

(cherry picked from commit 3cb7e7bf959dcd3b8080986c62e10a75c7af43f0)

1 files changed, 107 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/BPF/CORE/store-addr.ll b/llvm/test/CodeGen/BPF/CORE/store-addr.ll
new file mode 100644
index 00000000000..4b19c33e666
--- /dev/null
+++ b/llvm/test/CodeGen/BPF/CORE/store-addr.ll
@@ -0,0 +1,107 @@
+; RUN: llc -march=bpfel -filetype=asm -o - %s | FileCheck %s
+; RUN: llc -march=bpfel -mattr=+alu32 -filetype=asm -o - %s | FileCheck %s
+; Source code:
+;   struct t {
+;     int a;
+;   } __attribute__((preserve_access_index));
+;   int foo(void *);
+;   int test(struct t *arg) {
+;       long param[1];
+;       param[0] = (long)&arg->a;
+;       return foo(param);
+;   }
+; Compiler flag to generate IR:
+;   clang -target bpf -S -O2 -g -emit-llvm test.c
+
+%struct.t = type { i32 }
+
+; Function Attrs: nounwind
+define dso_local i32 @test(%struct.t* %arg) local_unnamed_addr #0 !dbg !14 {
+entry:
+  %param = alloca [1 x i64], align 8
+  call void @llvm.dbg.value(metadata %struct.t* %arg, metadata !22, metadata !DIExpression()), !dbg !27
+  %0 = bitcast [1 x i64]* %param to i8*, !dbg !28
+  call void @llvm.lifetime.start.p0i8(i64 8, i8* nonnull %0) #5, !dbg !28
+  call void @llvm.dbg.declare(metadata [1 x i64]* %param, metadata !23, metadata !DIExpression()), !dbg !29
+  %1 = tail call i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.ts(%struct.t* %arg, i32 0, i32 0), !dbg !30, !llvm.preserve.access.index !18
+  %2 = ptrtoint i32* %1 to i64, !dbg !31
+  %arrayidx = getelementptr inbounds [1 x i64], [1 x i64]* %param, i64 0, i64 0, !dbg !32
+  store i64 %2, i64* %arrayidx, align 8, !dbg !33, !tbaa !34
+  %call = call i32 @foo(i8* nonnull %0) #5, !dbg !38
+  call void @llvm.lifetime.end.p0i8(i64 8, i8* nonnull %0) #5, !dbg !39
+  ret i32 %call, !dbg !40
+}
+
+; CHECK:  r[[OFFSET:[0-9]+]] = 0
+; CHECK:  r1 += r[[OFFSET]]
+; CHECK:  *(u64 *)(r10 - 8) = r1
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) #2
+
+; Function Attrs: nounwind readnone
+declare i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.ts(%struct.t*, i32, i32) #3
+
+declare !dbg !5 dso_local i32 @foo(i8*) local_unnamed_addr #4
+
+; Function Attrs: argmemonly nounwind
+declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture) #2
+
+; Function Attrs: nounwind readnone speculatable
+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 }
+attributes #2 = { argmemonly nounwind }
+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 = !{!10, !11, !12}
+!llvm.ident = !{!13}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 11.0.0 (https://github.com/llvm/llvm-project.git 4f995959a05ae94cc4f9cc80035f7e4b3ecd2d88)", 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, !5}
+!4 = !DIBasicType(name: "long int", size: 64, encoding: DW_ATE_signed)
+!5 = !DISubprogram(name: "foo", scope: !1, file: !1, line: 4, type: !6, flags: DIFlagPrototyped, spFlags: DISPFlagOptimized, retainedNodes: !2)
+!6 = !DISubroutineType(types: !7)
+!7 = !{!8, !9}
+!8 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!9 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
+!10 = !{i32 7, !"Dwarf Version", i32 4}
+!11 = !{i32 2, !"Debug Info Version", i32 3}
+!12 = !{i32 1, !"wchar_size", i32 4}
+!13 = !{!"clang version 11.0.0 (https://github.com/llvm/llvm-project.git 4f995959a05ae94cc4f9cc80035f7e4b3ecd2d88)"}
+!14 = distinct !DISubprogram(name: "test", scope: !1, file: !1, line: 5, type: !15, scopeLine: 5, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !21)
+!15 = !DISubroutineType(types: !16)
+!16 = !{!8, !17}
+!17 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !18, size: 64)
+!18 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "t", file: !1, line: 1, size: 32, elements: !19)
+!19 = !{!20}
+!20 = !DIDerivedType(tag: DW_TAG_member, name: "a", scope: !18, file: !1, line: 2, baseType: !8, size: 32)
+!21 = !{!22, !23}
+!22 = !DILocalVariable(name: "arg", arg: 1, scope: !14, file: !1, line: 5, type: !17)
+!23 = !DILocalVariable(name: "param", scope: !14, file: !1, line: 6, type: !24)
+!24 = !DICompositeType(tag: DW_TAG_array_type, baseType: !4, size: 64, elements: !25)
+!25 = !{!26}
+!26 = !DISubrange(count: 1)
+!27 = !DILocation(line: 0, scope: !14)
+!28 = !DILocation(line: 6, column: 5, scope: !14)
+!29 = !DILocation(line: 6, column: 10, scope: !14)
+!30 = !DILocation(line: 7, column: 28, scope: !14)
+!31 = !DILocation(line: 7, column: 16, scope: !14)
+!32 = !DILocation(line: 7, column: 5, scope: !14)
+!33 = !DILocation(line: 7, column: 14, scope: !14)
+!34 = !{!35, !35, i64 0}
+!35 = !{!"long", !36, i64 0}
+!36 = !{!"omnipotent char", !37, i64 0}
+!37 = !{!"Simple C/C++ TBAA"}
+!38 = !DILocation(line: 8, column: 12, scope: !14)
+!39 = !DILocation(line: 9, column: 1, scope: !14)
+!40 = !DILocation(line: 8, column: 5, scope: !14)