[PATCH] D52055: [PPC64] Support relaxing R_PPC64_TLSGD16 in TlsGdtoLe relaxation

[Sean Fertile via Phabricator via llvm-commits]

sfertile created this revision.
sfertile added reviewers: syzaara, ruiu, MaskRay, rdhindsa.
Herald added subscribers: kbarton, arichardson, nemanjai, emaste.
Herald added a reviewer: espindola.

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 at tprel@ha`. The full transformation is:

gd:                                                                       le:

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


Repository:
  rLLD LLVM Linker

https://reviews.llvm.org/D52055

Files:
  ELF/Arch/PPC64.cpp
  test/ELF/ppc64-tls-gd-le-small.s


Index: test/ELF/ppc64-tls-gd-le-small.s
===================================================================
--- /dev/null
+++ test/ELF/ppc64-tls-gd-le-small.s
@@ -0,0 +1,61 @@
+# 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 --wide %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 --wide %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 at ha
+    addi  2, 2,  .TOC.-.Lgep at l
+    .localentry test, .-test
+    mflr 0
+    std 0, 16(1)
+    stdu 1, -32(1)
+    addi 3, 2, a at got@tlsgd
+    bl __tls_get_addr(a at tlsgd)
+    nop
+    lwz 3, 0(3)
+    addi 1, 1, 32
+    ld 0, 16(1)
+    mtlr 0
+    blr
+
+        .type a, @object
+        .section .tdata,"awT", at 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
Index: ELF/Arch/PPC64.cpp
===================================================================
--- ELF/Arch/PPC64.cpp
+++ ELF/Arch/PPC64.cpp
@@ -197,6 +197,7 @@
   case R_PPC64_GOT_TLSGD16_HA:
     write32(Loc - EndianOffset, 0x60000000); // nop
     break;
+  case R_PPC64_GOT_TLSGD16:
   case R_PPC64_GOT_TLSGD16_LO:
     write32(Loc - EndianOffset, 0x3c6d0000); // addis r3, r13
     relocateOne(Loc, R_PPC64_TPREL16_HA, Val);


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