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
92 lines
3.4 KiB
LLVM
92 lines
3.4 KiB
LLVM
; RUN: opt -O2 -mtriple=bpf-pc-linux %s | llvm-dis > %t1
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; RUN: llc -mcpu=v1 %t1 -o - | FileCheck -check-prefixes=CHECK-COMMON,CHECK %s
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; RUN: opt -O2 -mtriple=bpf-pc-linux -bpf-disable-avoid-speculation %s | llvm-dis > %t1
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; RUN: llc -mcpu=v1 %t1 -o - | FileCheck -check-prefixes=CHECK-COMMON,CHECK-DISABLE %s
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;
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; Source:
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; unsigned foo();
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; ptr test(ptr p) {
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; unsigned ret = foo();
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; if (ret <= 7)
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; p += ret;
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; return p;
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; }
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; Compilation flag:
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; clang -target bpf -O2 -S -emit-llvm -Xclang -disable-llvm-passes test.c
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; Function Attrs: nounwind
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define dso_local ptr @test(ptr %p) #0 {
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entry:
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%p.addr = alloca ptr, align 8
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%ret = alloca i32, align 4
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store ptr %p, ptr %p.addr, align 8, !tbaa !2
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call void @llvm.lifetime.start.p0(i64 4, ptr %ret) #3
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%call = call i32 @foo()
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store i32 %call, ptr %ret, align 4, !tbaa !6
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%0 = load i32, ptr %ret, align 4, !tbaa !6
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%cmp = icmp ule i32 %0, 7
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br i1 %cmp, label %if.then, label %if.end
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if.then: ; preds = %entry
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%1 = load i32, ptr %ret, align 4, !tbaa !6
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%2 = load ptr, ptr %p.addr, align 8, !tbaa !2
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%idx.ext = zext i32 %1 to i64
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%add.ptr = getelementptr i8, ptr %2, i64 %idx.ext
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store ptr %add.ptr, ptr %p.addr, align 8, !tbaa !2
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br label %if.end
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if.end: ; preds = %if.then, %entry
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%3 = load ptr, ptr %p.addr, align 8, !tbaa !2
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call void @llvm.lifetime.end.p0(i64 4, ptr %ret) #3
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ret ptr %3
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}
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; CHECK-COMMON: [[REG6:r[0-9]+]] = r1
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; CHECK-COMMON: call foo
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; CHECK: r0 <<= 32
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; CHECK: r0 >>= 32
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; CHECK: if r0 > 7 goto [[LABEL:.*]]
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; CHECK: [[REG6]] += r0
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; CHECK: [[LABEL]]:
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; CHECK: r0 = [[REG6]]
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; CHECK-DISABLE: [[REG1:r[0-9]+]] = r0
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; CHECK-DISABLE: [[REG1]] <<= 32
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; CHECK-DISABLE: [[REG1]] >>= 32
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; CHECK-DISABLE: [[REG2:r[0-9]+]] = 8
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; CHECK-DISABLE: if [[REG2]] > [[REG1]] goto [[LABEL:.*]]
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; CHECK-DISABLE: r0 = 0
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; CHECK-DISABLE: [[LABEL]]:
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; CHECK-DISABLE: r0 <<= 32
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; CHECK-DISABLE: r0 >>= 32
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; CHECK-DISABLE: [[REG6]] += r0
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; CHECK-DISABLE: r0 = [[REG6]]
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; CHECK-COMMON: exit
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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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declare dso_local i32 @foo(...) #2
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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 "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" }
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attributes #1 = { argmemonly nounwind willreturn }
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attributes #2 = { "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"="true" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
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attributes #3 = { 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 12.0.0 (https://github.com/llvm/llvm-project.git ca9c5433a6c31e372092fcd8bfd0e4fddd7e8784)"}
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!2 = !{!3, !3, i64 0}
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!3 = !{!"any pointer", !4, i64 0}
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!4 = !{!"omnipotent char", !5, i64 0}
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!5 = !{!"Simple C/C++ TBAA"}
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!6 = !{!7, !7, i64 0}
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!7 = !{!"int", !4, i64 0}
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