[LLVMdev] [Patch] Let MC/ELF generate Thumb/Thumb-2 are properly

[Jim Grosbach]

Hi Koan,

In general, this looks OK to me. Please split the patch into separate pieces, one for each issue you're addressing, though. From your description, it sounds like this should be 4 patches. That way we have a cleaner revision history in svn.

-Jim

On May 12, 2011, at 10:42 PM, Koan-Sin Tan wrote:

> Hi,
> 
> We are trying to use clang as a drop-in replacement for the gcc come with
> Android NDK. I found that MC/ELF doesn't not handle Thumb functions properly,
> e.g., bit 0 of the function name in the .symtab is not set to 1, and some thumb
> instructions are not generated correctly, e.g., the addresses for tBL/tBLX are
> not calculated right.
> 
> With that attached patch, we can compile and run some (not all) Android
> NDK samples without problem.
> 
> The attached initial patch
> 1. sets bit 0 of the function address of thumb function in .symtab
>   ("T is 1 if the target symbol S has type STT_FUNC and the
>   symbol addresses a Thumb instruction ;it is 0 otherwise."
>   from "ELF for the ARM Architecture" 4.7.1.2)
> 
> 2. fixes target address tBL and tBLX
> 3. sets relocation type of tBL/tBLX to R_ARM_THM_CALL
>    (4.7.1.6)
> 4. adds some attributes to attribute section when cpu is "xscale"
>   (this is what used in Android NDK, when architecture is ARMv5)
> 
> --
> // koan-sin tan
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