e018cbf720
There are two motivations. `-fno-pic -fstack-protector -mstack-protector-guard=global` created `__stack_chk_guard` is referenced directly on all ELF OSes except FreeBSD. This patch allows referencing the symbol indirectly with -fno-direct-access-external-data. Some Linux kernel folks want `-fno-pic -fstack-protector -mstack-protector-guard-reg=gs -mstack-protector-guard-symbol=__stack_chk_guard` created `__stack_chk_guard` to be referenced directly, avoiding R_X86_64_REX_GOTPCRELX (even if the relocation may be optimized out by the linker). https://github.com/llvm/llvm-project/issues/60116 Why they need this isn't so clear to me. --- Add module flag "direct-access-external-data" and set the dso_local property of the stack protector symbol. The module flag can benefit other LLVMCodeGen synthesized symbols that are not represented in LLVM IR. Nowadays, with `-fno-pic` being uncommon, ideally we should set "direct-access-external-data" when it is true. However, doing so would require ~90 clang/test tests to be updated, which are too much. As a compromise, we set "direct-access-external-data" only when it's different from the implied default value. Reviewed By: nickdesaulniers Differential Revision: https://reviews.llvm.org/D150841
32 lines
970 B
LLVM
32 lines
970 B
LLVM
; RUN: llc -mtriple=arm-- --relocation-model=rwpi %s -o - | \
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; RUN: FileCheck %s --check-prefixes=RWPI
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; RUN: llc -mtriple=arm-- --relocation-model=ropi %s -o - | \
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; RUN: FileCheck %s --check-prefixes=ROPI
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; RUN: llc -mtriple=arm-- --relocation-model=pic %s -o - | \
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; RUN: FileCheck %s --check-prefixes=PIC
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; RWPI: ldr {{r[0-9]+}}, .LCPI0_0
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; RWPI: .LCPI0_0:
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; RWPI-NEXT: .long __stack_chk_guard(sbrel)
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; ROPI: ldr {{r[0-9]+}}, .LCPI0_0
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; ROPI: .LCPI0_0:
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; ROPI-NEXT: .long __stack_chk_guard
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; PIC: ldr {{r[0-9]+}}, .LCPI0_0
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; PIC: .LCPI0_0:
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; PIC-NEXT: .Ltmp0:
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; PIC-NEXT: .long __stack_chk_guard(GOT_PREL)-((.LPC0_0+8)-.Ltmp0)
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define dso_local i32 @foo(i32 %t) nounwind sspstrong {
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entry:
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%vla = alloca i32, i32 %t
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%call = call i32 @baz(ptr %vla)
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ret i32 %call
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}
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declare dso_local i32 @baz(ptr)
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!llvm.module.flags = !{!0}
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!0 = !{i32 7, !"PIC Level", i32 2}
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