9ab9a9595b
The NS==0 condition used by D103717 missed a corner case: if the current copy
does not have a hash suffix (e.g. weak_odr), a copy with value profiling (with a
different CFG) may exist. This is super rare, but is possible with pre-inlining
PGO instrumentation (which can make a weak_odr function inlines its callees
differently, sometimes with value profiling while sometimes without).
If the current copy with private profd is prevailing, the non-prevailing copy
may get an undefined symbol if a caller inlining the non-prevailing function
references its profd. If the other copy with non-private profd is prevailing,
the current copy may cause a "relocation to discarded section" linker error.
The fix is straightforward: just keep non-private profd in such a `DataReferencedByCode` case.
With this change, a stage 2 (`-DLLVM_TARGETS_TO_BUILD=X86 -DLLVM_BUILD_INSTRUMENTED=IR`)
clang is 0.08% larger (172431496/172286720-1).
`stat -c %s **/*.o | awk '{s+=$1}END{print s}' is 0.026% larger.
The majority of D103717's benefits remains.
Reviewed By: xur
Differential Revision: https://reviews.llvm.org/D108432
30 lines
1.6 KiB
LLVM
30 lines
1.6 KiB
LLVM
;; Test comdat functions.
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; RUN: opt < %s -mtriple=x86_64-linux -passes=pgo-instr-gen,instrprof -S | FileCheck %s --check-prefixes=ELF
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; RUN: opt < %s -mtriple=x86_64-windows -passes=pgo-instr-gen,instrprof -S | FileCheck %s --check-prefixes=COFF
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$linkonceodr = comdat any
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$weakodr = comdat any
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;; profc/profd have hash suffixes. This definition doesn't have value profiling,
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;; so definitions with the same name in other modules must have the same CFG and
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;; cannot have value profiling, either. profd can be made private for ELF.
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; ELF: @__profc_linkonceodr.[[#]] = linkonce_odr hidden global {{.*}} comdat, align 8
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; ELF: @__profd_linkonceodr.[[#]] = private global {{.*}} comdat($__profc_linkonceodr.[[#]]), align 8
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; COFF: @__profc_linkonceodr.[[#]] = linkonce_odr hidden global {{.*}} comdat, align 8
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; COFF: @__profd_linkonceodr.[[#]] = linkonce_odr hidden global {{.*}} comdat, align 8
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define linkonce_odr void @linkonceodr() comdat {
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ret void
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}
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;; weakodr in a comdat is not renamed. There is no guarantee that definitions in
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;; other modules don't have value profiling. profd should be conservatively
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;; non-private to prevent a caller from referencing a non-prevailing profd,
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;; causing a linker error.
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; ELF: @__profc_weakodr = weak_odr hidden global {{.*}} comdat, align 8
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; ELF: @__profd_weakodr = weak_odr hidden global {{.*}} comdat($__profc_weakodr), align 8
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; COFF: @__profc_weakodr = weak_odr hidden global {{.*}} comdat, align 8
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; COFF: @__profd_weakodr = weak_odr hidden global {{.*}} comdat, align 8
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define weak_odr void @weakodr() comdat {
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ret void
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}
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