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Re: LTO bootstrap compare errors for ARM64

> As a First step I compared the "objump -D" dump between
> "stage2-gcc/gimple.o"  and "stage3-gcc/gimple.o".  Differences are in
> LTO sections .gnu.lto_.decls.0, .gnu.lto_.symtab.
> Ref:

If you see the differences already in .o files (i.e. at compile time), I think the next
step is to produce -fdump-tree-all -fdump-ipa-all dumps of stage2-gcc/gimple.o
and stage3-gcc/gimple.o and see how they differ.

Debugging misoptimization of LTO stage2 compiler will be interesting - I guess we can
first try to identify what is wrong rahter than usual bisecting method...

> No differences when when using "objdump -d".
> Next I passed "-save-temps" to stage2 and stage3 builds and compared
> the assembly files. The differences are in strings dumped via .ascii
> and ,string directives.
> Next I checked the flags passed to the stage 2 and stage 3 builds. It
> is same and below is the flag set being passed.
> -save-temps -O2 -g -flto -flto=jobserver -frandom-seed=1
> -ffat-lto-objects -DIN_GCC    -fno-exceptions -fno-rtti
> -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings
> -Wcast-qual -Wmissing-forma        t-attribute -pedantic
> -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings
>  Can you please suggest on how to fix/debug further these comparison
> failures in GCC 4.9?
> regards,
> Venkat.

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