[PATCH] [PowerPC] Fix __tls_get_addr sequence to avoid register assignment issues

[hfinkel at anl.gov]

Alright, here's what happening on the `P7`:

  Starting program: /home/hfinkel/build/ppc64/llvm-stage1/bin/clang-tblgen -gen-arm-neon -I /home/hfinkel/src/llvm/tools/clang/lib/Headers -I /home/hfinkel/src/llvm/lib/Target -I /home/hfinkel/src/llvm/include /home/hfinkel/src/llvm/tools/clang/include/clang/Basic/arm_neon.td -o /home/hfinkel/build/ppc64/llvm-stage1/tools/clang/lib/Headers/arm_neon.h.tmp
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib64/libthread_db.so.1".
  
  Program received signal SIGSEGV, Segmentation fault.
  0x000000001008d2a4 in .llvm::PrettyStackTraceEntry::PrettyStackTraceEntry() ()
  (gdb) disassemble
  Dump of assembler code for function ._ZN4llvm21PrettyStackTraceEntryC2Ev:
     0x000000001008d270 <+0>:   mflr    r0
     0x000000001008d274 <+4>:   std     r31,-8(r1)
     0x000000001008d278 <+8>:   std     r0,16(r1)
     0x000000001008d27c <+12>:  stdu    r1,-64(r1)
     0x000000001008d280 <+16>:  addis   r12,r2,-1
     0x000000001008d284 <+20>:  nop
     0x000000001008d288 <+24>:  mr      r4,r3
     0x000000001008d28c <+28>:  mr      r31,r1
     0x000000001008d290 <+32>:  addi    r3,r2,-32392
     0x000000001008d294 <+36>:  addi    r6,r12,-2248
     0x000000001008d298 <+40>:  bl      0x10005078 <00000011.plt_call.__tls_get_addr@@GLIBC_2.3+0>
     0x000000001008d29c <+44>:  ld      r2,40(r1)
     0x000000001008d2a0 <+48>:  addi    r5,r6,16
  => 0x000000001008d2a4 <+52>:  std     r5,0(r4)
     0x000000001008d2a8 <+56>:  addis   r3,r3,0
     0x000000001008d2ac <+60>:  ori     r2,r2,0
     0x000000001008d2b0 <+64>:  ld      r5,-32768(r3)
     0x000000001008d2b4 <+68>:  std     r5,8(r4)
     0x000000001008d2b8 <+72>:  std     r4,-32768(r3)
     0x000000001008d2bc <+76>:  addi    r1,r1,64
     0x000000001008d2c0 <+80>:  ld      r0,16(r1)
     0x000000001008d2c4 <+84>:  ld      r31,-8(r1)
     0x000000001008d2c8 <+88>:  mtlr    r0
     0x000000001008d2cc <+92>:  blr
     0x000000001008d2d0 <+96>:  .long 0x0
     0x000000001008d2d4 <+100>: .long 0x0
     0x000000001008d2d8 <+104>: .long 0x0
  End of assembler dump.

Looks to me like the instruction that becomes the function call needs to do more than clobber r3. Maybe it needs the full clobber mask associated with a regular function call? Based on this crash, it looks like it at least also clobbers r4.


http://reviews.llvm.org/D7491

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