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yonghong-songyonghong-song
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[BPF] Make -mcpu=v3 as the default (#107008)
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] #101428 [3] #106494
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‎clang/lib/Basic/Targets/BPF.cpp

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@@ -38,7 +38,10 @@ void BPFTargetInfo::getTargetDefines(const LangOptions &Opts,
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Builder.defineMacro("__BPF_FEATURE_ADDR_SPACE_CAST");
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if (CPU.empty() || CPU == "generic" || CPU == "v1") {
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if (CPU.empty())
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CPU = "v3";
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if (CPU == "generic" || CPU == "v1") {
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Builder.defineMacro("__BPF_CPU_VERSION__", "1");
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return;
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}

‎clang/test/Preprocessor/bpf-predefined-macros.c

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// RUN: %clang -E -target bpfel -x c -o - %s | FileCheck -check-prefix=CHECK -check-prefix=CPU_NO %s
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// RUN: %clang -E -target bpfeb -x c -o - %s | FileCheck -check-prefix=CHECK -check-prefix=CPU_NO %s
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// RUN: %clang -E -target bpfel -mcpu=v1 -x c -o - %s | FileCheck -check-prefix=CHECK -check-prefix=CPU_NO %s
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// RUN: %clang -E -target bpfeb -mcpu=v1 -x c -o - %s | FileCheck -check-prefix=CHECK -check-prefix=CPU_NO %s
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// RUN: %clang -E -target bpfel -mcpu=v1 -x c -o - %s | FileCheck -check-prefix=CHECK -check-prefix=CPU_V1 %s
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// RUN: %clang -E -target bpfel -mcpu=v2 -x c -o - %s | FileCheck -check-prefix=CHECK -check-prefix=CPU_V2 %s
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// RUN: %clang -E -target bpfel -mcpu=v3 -x c -o - %s | FileCheck -check-prefix=CHECK -check-prefix=CPU_V3 %s

‎llvm/lib/Target/BPF/BPFSubtarget.cpp

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@@ -65,6 +65,8 @@ void BPFSubtarget::initializeEnvironment() {
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}
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void BPFSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
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if (CPU.empty())
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CPU = "v3";
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if (CPU == "probe")
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CPU = sys::detail::getHostCPUNameForBPF();
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if (CPU == "generic" || CPU == "v1")

‎llvm/test/CodeGen/BPF/32-bit-subreg-cond-select.ll

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; RUN: llc -O2 -march=bpfel -mattr=+alu32 < %s | FileCheck %s
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; RUN: llc -O2 -march=bpfel -mcpu=v1 -mattr=+alu32 < %s | FileCheck %s
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;
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; unsigned int select_cc_32 (unsigned a, unsigned b, int c, int d)
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; {

‎llvm/test/CodeGen/BPF/CORE/field-reloc-bitfield-1-bpfeb.ll

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; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 3
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; RUN: opt -O2 -S < %s | llc -filetype=asm | FileCheck -check-prefixes=CHECK,CHECK-ALU64 %s
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; RUN: opt -O2 -S < %s | llc -mattr=+alu32 -filetype=asm | FileCheck -check-prefixes=CHECK,CHECK-ALU32 %s
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; RUN: opt -O2 -S < %s | llc -mcpu=v1 -filetype=asm | FileCheck -check-prefixes=CHECK,CHECK-ALU64 %s
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; RUN: opt -O2 -S < %s | llc -mcpu=v1 -mattr=+alu32 -filetype=asm | FileCheck -check-prefixes=CHECK,CHECK-ALU32 %s
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; Source code:
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; struct s {
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; unsigned long long f1;

‎llvm/test/CodeGen/BPF/CORE/field-reloc-bitfield-1.ll

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; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 3
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; RUN: opt -O2 -S < %s | llc -filetype=asm | FileCheck -check-prefixes=CHECK,CHECK-ALU64 %s
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; RUN: opt -O2 -S < %s | llc -mattr=+alu32 -filetype=asm | FileCheck -check-prefixes=CHECK,CHECK-ALU32 %s
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; RUN: opt -O2 -S < %s | llc -mcpu=v1 -filetype=asm | FileCheck -check-prefixes=CHECK,CHECK-ALU64 %s
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; RUN: opt -O2 -S < %s | llc -mcpu=v1 -mattr=+alu32 -filetype=asm | FileCheck -check-prefixes=CHECK,CHECK-ALU32 %s
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; Source code:
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; struct s {
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; unsigned long long f1;

‎llvm/test/CodeGen/BPF/CORE/field-reloc-bitfield-2-bpfeb.ll

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; RUN: opt -O2 %s | llvm-dis > %t1
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; RUN: llc -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-EB,CHECK-ALU64 %s
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; RUN: llc -mattr=+alu32 -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-EB,CHECK-ALU32 %s
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; RUN: llc -mcpu=v1 -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-EB,CHECK-ALU64 %s
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; RUN: llc -mcpu=v1 -mattr=+alu32 -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-EB,CHECK-ALU32 %s
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; Source code:
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; struct s {
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; char f1;

‎llvm/test/CodeGen/BPF/CORE/field-reloc-bitfield-2.ll

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; RUN: opt -O2 %s | llvm-dis > %t1
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; RUN: llc -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-EL,CHECK-ALU64 %s
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; RUN: llc -mattr=+alu32 -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-EL,CHECK-ALU32 %s
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; RUN: llc -mcpu=v1 -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-EL,CHECK-ALU64 %s
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; RUN: llc -mcpu=v1 -mattr=+alu32 -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-EL,CHECK-ALU32 %s
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; Source code:
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; struct s {
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; char f1;

‎llvm/test/CodeGen/BPF/CORE/intrinsic-fieldinfo-byte-size-1.ll

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; RUN: opt -O2 %s | llvm-dis > %t1
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; RUN: llc -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-ALU64 %s
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; RUN: llc -mattr=+alu32 -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-ALU32 %s
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; RUN: llc -mcpu=v1 -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-ALU64 %s
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; RUN: llc -mcpu=v1 -mattr=+alu32 -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-ALU32 %s
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; Source code:
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; typedef struct s1 { int a1:7; int a2:4; int a3:5; int a4:16;} __s1;
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; union u1 { int b1; __s1 b2; };

‎llvm/test/CodeGen/BPF/CORE/intrinsic-fieldinfo-byte-size-2.ll

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; RUN: opt -O2 %s | llvm-dis > %t1
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; RUN: llc -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-ALU64 %s
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; RUN: llc -mattr=+alu32 -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-ALU32 %s
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; RUN: llc -mcpu=v1 -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-ALU64 %s
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; RUN: llc -mcpu=v1 -mattr=+alu32 -filetype=asm -o - %t1 | FileCheck -check-prefixes=CHECK,CHECK-ALU32 %s
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; Source code:
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; typedef struct s1 { int a1; char a2; } __s1;
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; union u1 { int b1; __s1 b2; };

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