On Thu, Dec 24, 2015 at 02:03:16PM +0100, Ard Biesheuvel wrote: > The tiny code model for AARCH64 is the most efficient model, since its > symbol references are relative via a single 32-bit ADR instruction. This > gives us a range of only +/- 1 MB, but this is sufficient for the vast > majority of the modules that make up a typical EDK2 firmware. Since the > reference is relative, it does not result in a fixup entry in the PE/COFF > relocation table. Unlike the small code model, which uses ADRP instructions, > the tiny model does not impose section alignment requirements. > > However, in some cases, (e.g., the full Shell binary built in DEBUG mode) > the resulting binary exceeds 1 MB, which may result in build errors if > code at one end of the image references a symbol at the other end. > > Since the tiny and small code models can coexist in a single binary, we > can work around this problem by making sure that tiny model .text and > .data sections are emitted in close proximity to each other, by reducing > the function alignment for tiny model code (which by itself should also be > an improvement in terms of code size), and sorting the linker input by > alignment.
Hmm... > Contributed-under: TianoCore Contribution Agreement 1.0 > Signed-off-by: Ard Biesheuvel <[email protected]> > --- > BaseTools/Conf/tools_def.template | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/BaseTools/Conf/tools_def.template > b/BaseTools/Conf/tools_def.template > index 0cc85a6f359d..fbf0841fc91f 100644 > --- a/BaseTools/Conf/tools_def.template > +++ b/BaseTools/Conf/tools_def.template > @@ -4437,10 +4437,10 @@ DEFINE GCC49_ASM_FLAGS = > DEF(GCC48_ASM_FLAGS) > DEFINE GCC49_ARM_ASM_FLAGS = DEF(GCC48_ARM_ASM_FLAGS) > DEFINE GCC49_AARCH64_ASM_FLAGS = DEF(GCC48_AARCH64_ASM_FLAGS) > DEFINE GCC49_ARM_CC_FLAGS = DEF(GCC48_ARM_CC_FLAGS) > -DEFINE GCC49_AARCH64_CC_FLAGS = $(ARCHCC_FLAGS) $(PLATFORM_FLAGS) > DEF(GCC44_ALL_CC_FLAGS) -mcmodel=tiny DEF(GCC_AARCH64_CC_FLAGS) > +DEFINE GCC49_AARCH64_CC_FLAGS = $(ARCHCC_FLAGS) $(PLATFORM_FLAGS) > DEF(GCC44_ALL_CC_FLAGS) -mcmodel=tiny -falign-functions=4 > DEF(GCC_AARCH64_CC_FLAGS) My GCC manpage claims that "-Os disables the following optimization flags: -falign-functions ..." and -Os is set in GCC_ALL_CC_FLAGS, and as far as I can see not overridden for AARCH64, except for DEBUG builds. > DEFINE GCC49_ARM_DLINK_FLAGS = DEF(GCC48_ARM_DLINK_FLAGS) > DEFINE GCC49_ARM_DLINK2_FLAGS = DEF(GCC48_ARM_DLINK2_FLAGS) > -DEFINE GCC49_AARCH64_DLINK_FLAGS = DEF(GCC48_AARCH64_DLINK_FLAGS) > +DEFINE GCC49_AARCH64_DLINK_FLAGS = DEF(GCC48_AARCH64_DLINK_FLAGS) > --sort-section=alignment No objection to this one. > DEFINE GCC49_AARCH64_DLINK2_FLAGS = DEF(GCC48_AARCH64_DLINK2_FLAGS) > DEFINE GCC49_ARM_ASLDLINK_FLAGS = DEF(GCC48_ARM_ASLDLINK_FLAGS) > DEFINE GCC49_AARCH64_ASLDLINK_FLAGS = DEF(GCC48_AARCH64_ASLDLINK_FLAGS) > -- > 2.5.0 > _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
