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
45 lines
1.9 KiB
LLVM
45 lines
1.9 KiB
LLVM
; RUN: llc < %s -mtriple=thumbv7-apple-ios -relocation-model=pic -no-integrated-as | FileCheck %s -check-prefix=PIC
|
|
; RUN: llc < %s -mtriple=thumbv7-apple-ios -relocation-model=static -no-integrated-as | FileCheck %s -check-prefix=STATIC
|
|
; RUN: llc < %s -mtriple=thumbv7-apple-ios -relocation-model=dynamic-no-pic -no-integrated-as | FileCheck %s -check-prefix=DYNAMIC-NO-PIC
|
|
|
|
;PIC: foo2
|
|
;PIC: movw [[R0:r[0-9]+]], :lower16:(L___stack_chk_guard$non_lazy_ptr-([[LABEL0:LPC[0-9_]+]]+4))
|
|
;PIC: movt [[R0]], :upper16:(L___stack_chk_guard$non_lazy_ptr-([[LABEL0]]+4))
|
|
;PIC: [[LABEL0]]:
|
|
;PIC: add [[R0]], pc
|
|
;PIC: ldr [[R1:r[0-9]+]], [[[R0]]]
|
|
;PIC: ldr {{r[0-9]+}}, [[[R1]]]
|
|
|
|
;STATIC: foo2
|
|
;STATIC: movw [[R0:r[0-9]+]], :lower16:___stack_chk_guard
|
|
;STATIC: movt [[R0]], :upper16:___stack_chk_guard
|
|
;STATIC: ldr {{r[0-9]+}}, [[[R0]]]
|
|
|
|
;DYNAMIC-NO-PIC: foo2
|
|
;DYNAMIC-NO-PIC: movw [[R0:r[0-9]+]], :lower16:L___stack_chk_guard$non_lazy_ptr
|
|
;DYNAMIC-NO-PIC: movt [[R0]], :upper16:L___stack_chk_guard$non_lazy_ptr
|
|
;DYNAMIC-NO-PIC: ldr {{r[0-9]+}}, [[[R0]]]
|
|
|
|
; Function Attrs: nounwind ssp
|
|
define i32 @test_stack_guard_remat() #0 {
|
|
%a1 = alloca [256 x i32], align 4
|
|
call void @llvm.lifetime.start.p0(i64 1024, ptr %a1)
|
|
call void @foo3(ptr %a1) #3
|
|
call void asm sideeffect "foo2", "~{r0},~{r1},~{r2},~{r3},~{r4},~{r5},~{r6},~{r7},~{r8},~{r9},~{r10},~{r11},~{r12},~{sp},~{lr}"()
|
|
call void @llvm.lifetime.end.p0(i64 1024, ptr %a1)
|
|
ret i32 0
|
|
}
|
|
|
|
; Function Attrs: nounwind
|
|
declare void @llvm.lifetime.start.p0(i64, ptr nocapture)
|
|
|
|
declare void @foo3(ptr)
|
|
|
|
; Function Attrs: nounwind
|
|
declare void @llvm.lifetime.end.p0(i64, ptr nocapture)
|
|
|
|
attributes #0 = { nounwind ssp "less-precise-fpmad"="false" "frame-pointer"="all" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
|
|
|
|
!llvm.module.flags = !{!0}
|
|
!0 = !{i32 7, !"PIC Level", i32 2}
|