On Thu, Oct 25, 2018 at 11:53 AM Umesh Kalappa <umesh.kalap...@gmail.com> wrote:
>
> Hi All,
>
> For the below code (test.c)
>
> int foo()
> {
> printf("Hello World");
> }
>
> On linux :
> ccpc -mcpu=e6500 -mno-altivec -mabi=no-altivec -D_WRS_HARDWARE_FP
> -mabi=elfv2 -mcmodel=med -mhard-float -S test.c
>
> linux asm :
> the constant string fetched like
>
> addis 3,2,.LC0@toc@ha
> addi 3,3,.LC0@toc@l
>
> where offset signed 32 bit used relatively to toc base on linux as
> expected for the medium code model .
> and the relocation entry will be generated by gas :
> R_PPC64_TOC16_HA and R_PPC64_TOC16_LO
>
> For Windows :
>
> same command and windows asm looks like
>
> la 3,.LC0@toc(2)
>
> where offset used signed 16 bit used relatively to toc base why it so ?.
> and the relocation entry will be :
> R_PPC64_TOC16 (signed 16 bit offset )
>
> why this difference and when we greping the .md file and we found
> patterns (rs6000.md ) like
>
> ;; Largetoc support
> (define_insn "*largetoc_high"
> [(set (match_operand:DI 0 "gpc_reg_operand" "=b*r")
> (high:DI
> (unspec [(match_operand:DI 1 "" "")
> (match_operand:DI 2 "gpc_reg_operand" "b")]
> UNSPEC_TOCREL)))]
> "TARGET_ELF && TARGET_CMODEL != CMODEL_SMALL"
> "addis %0,%2,%1@toc@ha")
>
> (define_insn "*largetoc_high_aix<mode>"
> [(set (match_operand:P 0 "gpc_reg_operand" "=b*r")
> (high:P
> (unspec [(match_operand:P 1 "" "")
> (match_operand:P 2 "gpc_reg_operand" "b")]
> UNSPEC_TOCREL)))]
> "TARGET_XCOFF && TARGET_CMODEL != CMODEL_SMALL"
> "addis %0,%1@u(%2)")
>
> the above patterns answered the difference b/w windows and linux .
>
> Questions to the expert is that using the medium code model ,how we
> can get the same linux semantics on windows (without source code
> changes) ?
>
> or above distinguish patterns for a reason and which we are missing here ?
Linux uses the ELF file format and assembler syntax. AIX uses the AIX
file format and assembler syntax.
Windows uses PE file format and syntax, which is not supported in the
rs6000 or powerpcspe ports.
Are you asking about semantics or syntax? Which source code do you
not want to change? If you want to target PE assembler, GCC needs to
be taught about that syntax, or at least it needs to generate the ELF
syntax for Windows PE.
Thanks, David
