[lld] r250230 - [ELF2/PPC64] Fix the TOC save in the .plt stub

[Hal Finkel via llvm-commits]

----- Original Message -----
> From: "Rui Ueyama" <ruiu at google.com>
> To: "Hal Finkel" <hfinkel at anl.gov>
> Cc: "llvm-commits" <llvm-commits at lists.llvm.org>
> Sent: Tuesday, October 13, 2015 4:50:33 PM
> Subject: Re: [lld] r250230 - [ELF2/PPC64] Fix the TOC save in the .plt stub
> 
> 
> I'm curious what was the instruction the previous hex code encoded.
> Did it work with that wrong instruction?

It encoded the same instruction, but with the wrong save offset (0 instead of 40). This happened to work with a sufficiently-simple "hello world" program.

 -Hal

> 
> 
> On Tue, Oct 13, 2015 at 2:47 PM, Hal Finkel via llvm-commits <
> llvm-commits at lists.llvm.org > wrote:
> 
> 
> Author: hfinkel
> Date: Tue Oct 13 16:47:34 2015
> New Revision: 250230
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=250230&view=rev
> Log:
> [ELF2/PPC64] Fix the TOC save in the .plt stub
> 
> The comment was right, but the encoding was wrong (and, it seems, I
> forgot a
> test case for the .plt stub).
> 
> Modified:
> lld/trunk/ELF/Target.cpp
> lld/trunk/test/elf2/ppc64-toc-restore.s
> 
> Modified: lld/trunk/ELF/Target.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Target.cpp?rev=250230&r1=250229&r2=250230&view=diff
> ==============================================================================
> --- lld/trunk/ELF/Target.cpp (original)
> +++ lld/trunk/ELF/Target.cpp Tue Oct 13 16:47:34 2015
> @@ -271,7 +271,7 @@ void PPC64TargetInfo::writePltEntry(uint
> // be a pointer to the function descriptor in the .opd section. Using
> // this scheme is simpler, but requires an extra indirection per PLT
> dispatch.
> 
> - write32be(Buf, 0xf8410000); // std %r2, 40(%r1)
> + write32be(Buf, 0xf8410028); // std %r2, 40(%r1)
> write32be(Buf + 4, 0x3d620000 | applyPPCHa(Off)); // addis %r11, %r2,
> X at ha
> write32be(Buf + 8, 0xe98b0000 | applyPPCLo(Off)); // ld %r12,
> X at l(%r11)
> write32be(Buf + 12, 0xe96c0000); // ld %r11,0(%r12)
> 
> Modified: lld/trunk/test/elf2/ppc64-toc-restore.s
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf2/ppc64-toc-restore.s?rev=250230&r1=250229&r2=250230&view=diff
> ==============================================================================
> --- lld/trunk/test/elf2/ppc64-toc-restore.s (original)
> +++ lld/trunk/test/elf2/ppc64-toc-restore.s Tue Oct 13 16:47:34 2015
> @@ -52,4 +52,11 @@ last:
> 
> // CHECK: Disassembly of section .plt:
> // CHECK: .plt:
> -// CHECK: 20020:
> +// CHECK: 20020: f8 41 00 28 std 2, 40(1)
> +// CHECK: 20024: 3d 62 00 00 addis 11, 2, 0
> +// CHECK: 20028: e9 8b 80 00 ld 12, -32768(11)
> +// CHECK: 2002c: e9 6c 00 00 ld 11, 0(12)
> +// CHECK: 20030: 7d 69 03 a6 mtctr 11
> +// CHECK: 20034: e8 4c 00 08 ld 2, 8(12)
> +// CHECK: 20038: e9 6c 00 10 ld 11, 16(12)
> +// CHECK: 2003c: 4e 80 04 20 bctr
> 
> 
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> 

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory