03958680b2
Currently, with the following example,
$ cat t.c
void foo(int a, _Atomic int *b)
{
*b &= a;
}
$ clang --target=bpf -O2 -c -mcpu=v3 t.c
$ llvm-objdump -d t.o
t.o: file format elf64-bpf
Disassembly of section .text:
0000000000000000 <foo>:
0: c3 12 00 00 51 00 00 00 <unknown>
1: 95 00 00 00 00 00 00 00 exit
Basically, the default cpu for llvm-objdump is v1 and it won't be able
to decode insn properly.
If we add --mcpu=v3 to llvm-objdump command line, we will have
$ llvm-objdump -d --mcpu=v3 t.o
t.o: file format elf64-bpf
Disassembly of section .text:
0000000000000000 <foo>:
0: c3 12 00 00 51 00 00 00 w1 = atomic_fetch_and((u32 *)(r2 + 0x0), w1)
1: 95 00 00 00 00 00 00 00 exit
The atomic_fetch_and insn can be decoded properly. Using latest cpu
version --mcpu=v4 can also decode properly like the above --mcpu=v3.
To avoid the above '<unknown>' decoding with common 'llvm-objdump -d
t.o', this patch marked the default cpu for llvm-objdump with the
current highest cpu number v4 in ELFObjectFileBase::tryGetCPUName(). The
cpu number in ELFObjectFileBase::tryGetCPUName() will be adjusted in the
future if cpu number is increased e.g. v5 etc. Such an approach also
aligns with gcc-bpf as discussed in [1].
Six bpf unit tests are affected with this change. I changed test output
for three unit tests and added --mcpu=v1 for the other three unit tests,
to demonstrate the default (cpu v4) behavior and explicit --mcpu=v1
behavior.
[1]
https://lore.kernel.org/bpf/6f32c0a1-9de2-4145-92ea-be025362182f@linux.dev/T/#m0f7e63c390bc8f5a5523e7f2f0537becd4205200
Co-authored-by: Yonghong Song <yonghong.song@linux.dev>
66 lines
2.3 KiB
LLVM
66 lines
2.3 KiB
LLVM
; RUN: llc -mtriple=bpfel -filetype=obj -o - %s | llvm-objdump --no-print-imm-hex -d - | FileCheck --check-prefix=CHECK-DEC %s
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; RUN: llc -mtriple=bpfel -filetype=obj -o - %s | llvm-objdump -d --print-imm-hex - | FileCheck --check-prefix=CHECK-HEX %s
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; Source Code:
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; int gbl;
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; int test(unsigned long long a, unsigned long long b) {
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; int ret = 0;
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; if (a == 0xABCDABCDabcdabcdULL) {
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; gbl = gbl * gbl * 2;
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; ret = 1;
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; goto out;
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; }
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; if (b == 0xABCDabcdabcdULL) {
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; gbl = gbl * 4;
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; ret = 2;
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; }
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; out:
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; return ret;
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; }
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@gbl = common local_unnamed_addr global i32 0, align 4
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; Function Attrs: norecurse nounwind
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define i32 @test(i64, i64) local_unnamed_addr #0 {
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; CHECK-LABEL: test
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%3 = icmp eq i64 %0, -6067004223159161907
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br i1 %3, label %4, label %8
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; CHECK-DEC: 18 03 00 00 cd ab cd ab 00 00 00 00 cd ab cd ab r3 = -6067004223159161907 ll
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; CHECK-DEC: 5d 31 07 00 00 00 00 00 if r1 != r3 goto +7
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; CHECK-HEX: 18 03 00 00 cd ab cd ab 00 00 00 00 cd ab cd ab r3 = -0x5432543254325433 ll
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; CHECK-HEX: 5d 31 07 00 00 00 00 00 if r1 != r3 goto +0x7
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; <label>:4: ; preds = %2
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%5 = load i32, ptr @gbl, align 4
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%6 = shl i32 %5, 1
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; CHECK-DEC: 67 01 00 00 01 00 00 00 r1 <<= 1
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; CHECK-HEX: 67 01 00 00 01 00 00 00 r1 <<= 0x1
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%7 = mul i32 %6, %5
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br label %13
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; <label>:8: ; preds = %2
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%9 = icmp eq i64 %1, 188899839028173
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; CHECK-DEC: 18 01 00 00 cd ab cd ab 00 00 00 00 cd ab 00 00 r1 = 188899839028173 ll
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; CHECK-HEX: 18 01 00 00 cd ab cd ab 00 00 00 00 cd ab 00 00 r1 = 0xabcdabcdabcd ll
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br i1 %9, label %10, label %16
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; <label>:10: ; preds = %8
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%11 = load i32, ptr @gbl, align 4
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%12 = shl nsw i32 %11, 2
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br label %13
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; <label>:13: ; preds = %4, %10
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%14 = phi i32 [ %12, %10 ], [ %7, %4 ]
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%15 = phi i32 [ 2, %10 ], [ 1, %4 ]
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store i32 %14, ptr @gbl, align 4
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; CHECK-DEC: 63 12 00 00 00 00 00 00 *(u32 *)(r2 + 0) = w1
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; CHECK-HEX: 63 12 00 00 00 00 00 00 *(u32 *)(r2 + 0x0) = w1
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br label %16
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; <label>:16: ; preds = %13, %8
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%17 = phi i32 [ 0, %8 ], [ %15, %13 ]
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ret i32 %17
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}
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attributes #0 = { norecurse nounwind }
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