Re: How to make gcc generate optimized code for statically linked TLS

Thank you,

with -ftls-model=local-exec gcc emits code that calculates offset at link time:

threadedVar = 0xDEAD; 1125c: d53bd041 mrs x1, tpidr_el0 11260: 91401020 add x0, x1, #0x4, lsl #12 11264: 9105a000 add x0, x0, #0x168 11268: 529bd5a2 movz w2, #0xdead 1126c: b9000002 str w2, [x0]

On Sun, Jul 14, 2013 at 10:30 AM, Pinski, Andrew < Andrew.Pinski@caviumnetworks.com> wrote:

Yes don't compile with -fPIC or compile with -ftls-model=local-exec .

Thanks, Andrew Pinski

---

*From:* linaro-toolchain-bounces@lists.linaro.org < linaro-toolchain-bounces@lists.linaro.org> on behalf of Vitali Sokhin < vitali.sokhin@gmail.com> *Sent:* Sunday, July 14, 2013 12:21 AM *To:* linaro-toolchain@lists.linaro.org *Subject:* How to make gcc generate optimized code for statically linked TLS

Hello,

I use gcc-linaro-aarch64-linux-gnu-4.8 to compile my C code with thread-local variables.

Here is an example of my C code:

__thread u32 threadedVar; void test(void) { threadedVar = 0xDEAD; }

gcc produces the following assembly to access my threaded variable:

threadedVar = 0xDEAD;
72b0:       d00000c0        adrp    x0, 21000
72b4:       f945ac00        ldr     x0, [x0,#2904]
72b8:       d503201f        nop
72bc:       d503201f        nop
72c0:       d53bd041        mrs     x1, tpidr_el0
72c4:       529bd5a2        movz    w2, #0xdead
72c8:       b8206822        str     w2, [x1,x0]

This assembly fits dynamically linked code, but in my case I have statically linked application that does not load any additional modules. Since I have exactly one TLS block containing all thread-local variable gcc should be able to calculate the offset at link time.

Can I make gcc to produce the following assembly ?

threadedVar = 0xDEAD; 72c0: d53bd041 mrs x1, tpidr_el0 72c4: 529bd5a2 movz w2, #0xdead 72c8: b8206822 str w2, [x1,#offset_to_threadedVar]

Thank you, Vitali