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
86 lines
2.6 KiB
LLVM
86 lines
2.6 KiB
LLVM
; RUN: opt -O2 -S -mtriple=bpf-pc-linux %s -o %t1
|
|
; RUN: llc %t1 -mcpu=v1 -o - | FileCheck -check-prefixes=CHECK,CHECK-V1 %s
|
|
; RUN: opt -O2 -S -mtriple=bpf-pc-linux %s -o %t1
|
|
; RUN: llc %t1 -mcpu=v3 -o - | FileCheck -check-prefixes=CHECK,CHECK-V3 %s
|
|
;
|
|
; Source:
|
|
; int test1(unsigned long a) {
|
|
; if ((unsigned)a <= 3) return 2;
|
|
; return 3;
|
|
; }
|
|
; int test2(unsigned long a) {
|
|
; if ((unsigned)a < 4) return 2;
|
|
; return 3;
|
|
; }
|
|
; Compilation flag:
|
|
; clang -target bpf -O2 -S -emit-llvm -Xclang -disable-llvm-passes test.c
|
|
|
|
; Function Attrs: nounwind
|
|
define dso_local i32 @test1(i64 %a) #0 {
|
|
entry:
|
|
%retval = alloca i32, align 4
|
|
%a.addr = alloca i64, align 8
|
|
store i64 %a, ptr %a.addr, align 8, !tbaa !3
|
|
%0 = load i64, ptr %a.addr, align 8, !tbaa !3
|
|
%conv = trunc i64 %0 to i32
|
|
%cmp = icmp ule i32 %conv, 3
|
|
br i1 %cmp, label %if.then, label %if.end
|
|
|
|
if.then: ; preds = %entry
|
|
store i32 2, ptr %retval, align 4
|
|
br label %return
|
|
|
|
if.end: ; preds = %entry
|
|
store i32 3, ptr %retval, align 4
|
|
br label %return
|
|
|
|
return: ; preds = %if.end, %if.then
|
|
%1 = load i32, ptr %retval, align 4
|
|
ret i32 %1
|
|
}
|
|
|
|
; CHECK-LABEL: test1
|
|
; CHECK-V1: if r[[#]] > r[[#]] goto
|
|
; CHECK-V3: if w[[#]] < 4 goto
|
|
|
|
; Function Attrs: nounwind
|
|
define dso_local i32 @test2(i64 %a) #0 {
|
|
entry:
|
|
%retval = alloca i32, align 4
|
|
%a.addr = alloca i64, align 8
|
|
store i64 %a, ptr %a.addr, align 8, !tbaa !3
|
|
%0 = load i64, ptr %a.addr, align 8, !tbaa !3
|
|
%conv = trunc i64 %0 to i32
|
|
%cmp = icmp ult i32 %conv, 4
|
|
br i1 %cmp, label %if.then, label %if.end
|
|
|
|
if.then: ; preds = %entry
|
|
store i32 2, ptr %retval, align 4
|
|
br label %return
|
|
|
|
if.end: ; preds = %entry
|
|
store i32 3, ptr %retval, align 4
|
|
br label %return
|
|
|
|
return: ; preds = %if.end, %if.then
|
|
%1 = load i32, ptr %retval, align 4
|
|
ret i32 %1
|
|
}
|
|
|
|
; CHECK-LABEL: test2
|
|
; CHECK-V1: if r[[#]] > r[[#]] goto
|
|
; CHECK-V3: if w[[#]] < 4 goto
|
|
|
|
attributes #0 = { nounwind "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" }
|
|
|
|
!llvm.module.flags = !{!0, !1}
|
|
!llvm.ident = !{!2}
|
|
|
|
!0 = !{i32 1, !"wchar_size", i32 4}
|
|
!1 = !{i32 7, !"frame-pointer", i32 2}
|
|
!2 = !{!"clang version 14.0.0 (https://github.com/llvm/llvm-project.git b7892f95881c891032742e0cd81861b845512653)"}
|
|
!3 = !{!4, !4, i64 0}
|
|
!4 = !{!"long", !5, i64 0}
|
|
!5 = !{!"omnipotent char", !6, i64 0}
|
|
!6 = !{!"Simple C/C++ TBAA"}
|