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a6c7bc9945
If users tried to have a structure decl/init code like below
struct test_t t = { .memeber1 = 45 };
It is very likely that compiler will generate a readonly section
to hold up the init values for variable t. Later load of t members,
e.g., t.member1 will result in a read from readonly section.
BPF program cannot handle relocation. This will force users to
write:
struct test_t t = {};
t.member1 = 45;
This is just inconvenient and unintuitive.
This patch addresses this issue by implementing BPF PreprocessISelDAG.
For any load from a global constant structure or an global array of
constant struct, it attempts to
translate it into a constant directly. The traversal of the
constant struct and other constant data structures are similar
to where the assembler emits read-only sections.
Four different unit test cases are also added to cover
different scenarios.
Signed-off-by: Yonghong Song <yhs@fb.com>
llvm-svn: 305560
42 lines
1.4 KiB
LLVM
42 lines
1.4 KiB
LLVM
; REQUIRES: x86_64-linux
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; RUN: llc < %s -march=bpfel -verify-machineinstrs | FileCheck --check-prefix=CHECK-EL %s
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; RUN: llc < %s -march=bpfeb -verify-machineinstrs | FileCheck --check-prefix=CHECK-EB %s
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;
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; This test requires little-endian host, so we specific x86_64-linux here.
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; Source code:
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; struct test_t1 {
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; char a;
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; int b, c, d;
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; };
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;
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; struct test_t1 g;
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; int test()
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; {
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; struct test_t1 t1 = {.a = 1};
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; g = t1;
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; return 0;
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; }
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%struct.test_t1 = type { i8, i32, i32, i32 }
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@test.t1 = private unnamed_addr constant %struct.test_t1 { i8 1, i32 0, i32 0, i32 0 }, align 4
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@g = common local_unnamed_addr global %struct.test_t1 zeroinitializer, align 4
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; Function Attrs: nounwind
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define i32 @test() local_unnamed_addr #0 {
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entry:
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tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* getelementptr inbounds (%struct.test_t1, %struct.test_t1* @g, i64 0, i32 0), i8* getelementptr inbounds (%struct.test_t1, %struct.test_t1* @test.t1, i64 0, i32 0), i64 16, i32 4, i1 false)
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; CHECK-EL: r2 = 1
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; CHECK-EL: *(u32 *)(r1 + 0) = r2
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; CHECK-EB: r2 = 16777216
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; CHECK-EB: *(u32 *)(r1 + 0) = r2
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ret i32 0
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}
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; CHECK-EL: .section .rodata.cst16,"aM",@progbits,16
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; CHECK-EB: .section .rodata.cst16,"aM",@progbits,16
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declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture writeonly, i8* nocapture readonly, i64, i32, i1) #1
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attributes #0 = { nounwind }
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attributes #1 = { argmemonly nounwind }
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