[PPC64] Thread-local storage general-dynamic to initial-exec relaxation.

Patch adds support for relaxing the general-dynamic tls sequence to
initial-exec.

the relaxation performs the following transformation:
addis r3, r2, x@got@tlsgd@ha --> addis r3, r2, x@got@tprel@ha
addi r3, r3, x@got@tlsgd@l   --> ld r3, x@got@tprel@l(r3)
bl __tls_get_addr(x@tlsgd)   --> nop
nop                          --> add r3, r3, r13

and instead of emitting a DTPMOD64/DTPREL64 pair for x, we emit a single
R_PPC64_TPREL64.

Differential Revision: https://reviews.llvm.org/D48090

1 files changed, 8 insertions, 0 deletions

diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index 33f4f25658f..aec9cd1af23 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -504,6 +504,7 @@ static uint64_t getRelocTargetVA(const InputFile *File, RelType Type, int64_t A,
   case R_RELAX_TLS_GD_TO_IE_END:
     return Sym.getGotOffset() + A - InX::Got->getSize();
   case R_GOT_OFF:
+  case R_RELAX_TLS_GD_TO_IE_GOT_OFF:
     return Sym.getGotOffset() + A;
   case R_GOT_PAGE_PC:
   case R_RELAX_TLS_GD_TO_IE_PAGE_PC:
@@ -773,11 +774,18 @@ void InputSectionBase::relocateAlloc(uint8_t *Buf, uint8_t *BufEnd) {
       break;
     case R_RELAX_TLS_GD_TO_IE:
     case R_RELAX_TLS_GD_TO_IE_ABS:
+    case R_RELAX_TLS_GD_TO_IE_GOT_OFF:
     case R_RELAX_TLS_GD_TO_IE_PAGE_PC:
     case R_RELAX_TLS_GD_TO_IE_END:
       Target->relaxTlsGdToIe(BufLoc, Type, TargetVA);
       break;
     case R_PPC_CALL:
+      // If this is a call to __tls_get_addr, it may be part of a TLS
+      // sequence that has been relaxed and turned into a nop. In this
+      // case, we don't want to handle it as a call.
+      if (read32(BufLoc) == 0x60000000) // nop
+        break;
+
       // Patch a nop (0x60000000) to a ld.
       if (Rel.Sym->NeedsTocRestore) {
         if (BufLoc + 8 > BufEnd || read32(BufLoc + 4) != 0x60000000) {