[PPC64] Support relaxing R_PPC64_TLSGD16 in TlsGdtoLe relaxation

[sfertile]

Summary

A General-dynamic tls access can be written using a R_PPC64_TLSGD16 relocation if the target got entry is within 16 bits of the TOC-base. This patch adds support for R_PPC64_TLSGD16 by relaxing it the same as a R_PPC64_GOT_TLSGD16_LO, ie rewriting the instruction to an addis 3, 13, a@tprel@ha. The full transformation is:

gd: le:

addi 3,2,a@got@tlsgd                           --> addis 3, 13, a@tprel@ha
bl __tls_get_addr(a@tlsgd)                   --> nop
nop                                                             --> addi 3, 3, a@tprel@l

[ruiu]

LGTM

[MaskRay]

test/ELF/ppc64-tls-gd-le-small.s

8

Do not have a strong opinion here.. But do you want to use the short form -r?

--wide -W is actually an ignored option in llvm-readelf.

https://github.com/llvm-mirror/llvm/tree/master/tools/llvm-readobj/llvm-readobj.cpp#L52

[sfertile]

test/ELF/ppc64-tls-gd-le-small.s

8

I removed the --wide, but left the --relocations for now following the discussion on D52124.

ELF/Arch/PPC64.cpp

void PPC64::relaxTlsGdToLe(uint8_t *Loc, RelType Type, uint64_t Val) const {
   // addi  r3, r3, x@got@tlsgd@l     into      addis r3, r13, x@tprel@ha
   // bl __tls_get_addr(x@tlsgd)      into      nop
   // nop                             into      addi r3, r3, x@tprel@l
 
   switch (Type) {
   case R_PPC64_GOT_TLSGD16_HA:
     writeInstrFromHalf16(Loc, 0x60000000); // nop
     break;
+  case R_PPC64_GOT_TLSGD16:
   case R_PPC64_GOT_TLSGD16_LO:
     writeInstrFromHalf16(Loc, 0x3c6d0000); // addis r3, r13
     relocateOne(Loc, R_PPC64_TPREL16_HA, Val);
     break;
   case R_PPC64_TLSGD:
     write32(Loc, 0x60000000);     // nop
     write32(Loc + 4, 0x38630000); // addi r3, r3
     // Since we are relocating a half16 type relocation and Loc + 4 points to

test/ELF/ppc64-tls-gd-le-small.s

+# REQUIRES: ppc
+
+# RUN: llvm-mc -filetype=obj -triple=powerpc64le-unknown-linux %s -o %t.o
+# RUN: llvm-objdump -d -r %t.o | FileCheck --check-prefix=CHECK-INPUT %s
+# RUN: ld.lld  --defsym __tls_get_addr=0x1001000 %t.o -o %t
+# RUN: llvm-objdump -d %t | FileCheck --check-prefix=CHECK-DIS %s
+# RUN: llvm-readelf -relocations %t | FileCheck --check-prefix=DYN-RELOCS %s
+
+# RUN: llvm-mc -filetype=obj -triple=powerpc64-unknown-linux %s -o %t.o
+# RUN: llvm-objdump -d -r %t.o | FileCheck --check-prefix=CHECK-INPUT %s
+# RUN: ld.lld  --defsym __tls_get_addr=0x1001000 %t.o -o %t
+# RUN: llvm-objdump -d %t | FileCheck --check-prefix=CHECK-DIS %s
+# RUN: llvm-readelf -relocations %t | FileCheck --check-prefix=DYN-RELOCS %s
+
+# Test checks the relaxation of a 'small' general-dynamic tls access into a
+# local-exec tls access.
+
+        .text
+        .abiversion 2
+
+        .global test
+        .p2align    4
+        .type test, @function
+
+test:
+.Lgep:
+    addis 2, 12, .TOC.-.Lgep@ha
+    addi  2, 2,  .TOC.-.Lgep@l
+    .localentry test, .-test
+    mflr 0
+    std 0, 16(1)
+    stdu 1, -32(1)
+    addi 3, 2, a@got@tlsgd
+    bl __tls_get_addr(a@tlsgd)
+    nop
+    lwz 3, 0(3)
+    addi 1, 1, 32
+    ld 0, 16(1)
+    mtlr 0
+    blr
+
+        .type a, @object
+        .section .tdata,"awT",@progbits
+        .global a
+        .p2align 2
+a:
+        .long 55
+        .size a, 4
+
+# CHECK-INPUT:       addi 3, 2, 0
+# CHECK-INPUT-NEXT:  R_PPC64_GOT_TLSGD16  a
+# CHECK-INPUT-NEXT:  bl .+0
+# CHECK-INPUT-NEXT:  R_PPC64_TLSGD        a
+# CHECK-INPUT-NEXT:  R_PPC64_REL24        __tls_get_addr
+
+# CHECK-DIS:      addis 3, 13, 0
+# CHECK-DIS-NEXT: nop
+# CHECK-DIS-NEXT: addi  3, 3, -28672
+# CHECK-DIS-NEXT: lwz 3, 0(3)
+
+# DYN-RELOCS: There are no relocations in this file