7852ebc088
Before llvm20, (void)__sync_fetch_and_add(...) always generates locked xadd insns. In linux kernel upstream discussion [1], it is found that for arm64 architecture, the original semantics of (void)__sync_fetch_and_add(...), i.e., __atomic_fetch_add(...), is preferred in order for jit to emit proper native barrier insns. In llvm commits [2] and [3], (void)__sync_fetch_and_add(...) will generate the following insns: - for cpu v1/v2: locked xadd insns to keep backward compatibility - for cpu v3/v4: __atomic_fetch_add() insns To ensure proper barrier semantics for (void)__sync_fetch_and_add(...), cpu v3/v4 is recommended. This patch enables cpu=v3 as the default cpu version. For users wanting to use cpu v1, -mcpu=v1 needs to be explicitly added to clang/llc command line. [1] https://lore.kernel.org/bpf/ZqqiQQWRnz7H93Hc@google.com/T/#mb68d67bc8f39e35a0c3db52468b9de59b79f021f [2] https://github.com/llvm/llvm-project/pull/101428 [3] https://github.com/llvm/llvm-project/pull/106494
66 lines
2.8 KiB
LLVM
66 lines
2.8 KiB
LLVM
; RUN: llc -march=bpfel -mcpu=v1 -o - %s | FileCheck %s
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; RUN: llc -march=bpfeb -mcpu=v1 -o - %s | FileCheck %s
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; Source code:
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; struct ipv6_key_t {
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; unsigned pid;
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; unsigned __int128 saddr;
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; unsigned short lport;
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; };
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;
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; extern void test1(ptr);
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; int test(int pid) {
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; struct ipv6_key_t ipv6_key = {.pid = pid};
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; test1(&ipv6_key);
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; return 0;
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; }
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; Compilation flag:
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; clang -target bpf -O2 -S -emit-llvm t.c
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%struct.ipv6_key_t = type { i32, i128, i16 }
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; Function Attrs: nounwind
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define dso_local i32 @test(i32 %pid) local_unnamed_addr #0 {
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entry:
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%ipv6_key = alloca %struct.ipv6_key_t, align 16
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call void @llvm.lifetime.start.p0(i64 48, ptr nonnull %ipv6_key) #4
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call void @llvm.memset.p0.i64(ptr nonnull align 16 dereferenceable(48) %ipv6_key, i8 0, i64 48, i1 false)
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store i32 %pid, ptr %ipv6_key, align 16, !tbaa !2
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call void @test1(ptr nonnull %ipv6_key) #4
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call void @llvm.lifetime.end.p0(i64 48, ptr nonnull %ipv6_key) #4
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ret i32 0
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}
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; CHECK-LABEL: test
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; CHECK: *(u64 *)(r10 - 48) = r{{[0-9]+}}
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; CHECK: *(u32 *)(r10 - 48) = r{{[0-9]+}}
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; Function Attrs: argmemonly nounwind willreturn
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declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture) #1
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; Function Attrs: argmemonly nounwind willreturn writeonly
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declare void @llvm.memset.p0.i64(ptr nocapture writeonly, i8, i64, i1 immarg) #2
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declare dso_local void @test1(ptr) local_unnamed_addr #3
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; Function Attrs: argmemonly nounwind willreturn
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declare void @llvm.lifetime.end.p0(i64 immarg, ptr nocapture) #1
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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" }
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attributes #1 = { argmemonly nounwind willreturn }
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attributes #2 = { argmemonly nounwind willreturn writeonly }
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attributes #3 = { "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" }
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attributes #4 = { nounwind }
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!llvm.module.flags = !{!0}
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!llvm.ident = !{!1}
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!0 = !{i32 1, !"wchar_size", i32 4}
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!1 = !{!"clang version 11.0.0 (https://github.com/llvm/llvm-project.git 55fc7a47f8f18f84b44ff16f4e7a420c0a42ddf1)"}
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!2 = !{!3, !4, i64 0}
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!3 = !{!"ipv6_key_t", !4, i64 0, !7, i64 16, !8, i64 32}
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!4 = !{!"int", !5, i64 0}
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!5 = !{!"omnipotent char", !6, i64 0}
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!6 = !{!"Simple C/C++ TBAA"}
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!7 = !{!"__int128", !5, i64 0}
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!8 = !{!"short", !5, i64 0}
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