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ANDROID: kbuild: merge module sections with LTO

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LLD always splits sections with LTO, which increases module sizes. This
change adds a linker script that merges the split sections in the final
module.

Bug: 145297228
Change-Id: I247e8bd029bd0f98a4fa1cd4db7f6398467b8e55
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
This commit is contained in:
Sami Tolvanen 2019-12-03 15:56:24 -08:00 committed by Alistair Delva
parent f0723e3bd5
commit 6cea04778e
2 changed files with 24 additions and 0 deletions
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2
Makefile
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@ -821,6 +821,8 @@ lto-clang-flags := -flto
endif
lto-clang-flags += -fvisibility=default $(call cc-option, -fsplit-lto-unit)
KBUILD_LDS_MODULE += $(srctree)/scripts/module-lto.lds
# allow disabling only clang LTO where needed
DISABLE_LTO_CLANG := -fno-lto
export DISABLE_LTO_CLANG

22
scripts/module-lto.lds Normal file
View file

@ -0,0 +1,22 @@
/*
* With CONFIG_LTO_CLANG, LLD always enables -fdata-sections and
* -ffunction-sections, which increases the size of the final module.
* Merge the split sections in the final binary.
*/
SECTIONS {
/*
* LLVM may emit .eh_frame with CONFIG_CFI_CLANG despite
* -fno-asynchronous-unwind-tables. Discard the section.
*/
/DISCARD/ : {
*(.eh_frame)
}
.bss : { *(.bss .bss[.0-9a-zA-Z_]*) }
.data : { *(.data .data[.0-9a-zA-Z_]*) }
.rela.data : { *(.rela.data .rela.data[.0-9a-zA-Z_]*) }
.rela.rodata : { *(.rela.rodata .rela.rodata[.0-9a-zA-Z_]*) }
.rela.text : { *(.rela.text .rela.text[.0-9a-zA-Z_]*) }
.rodata : { *(.rodata .rodata[.0-9a-zA-Z_]*) }
.text : { *(.text .text[.0-9a-zA-Z_]*) }
}