[PPC64] toc-indirect to toc-relative relaxation

This is based on D54720 by Sean Fertile.

When accessing a global symbol which is not defined in the translation unit,
compilers will generate instructions that load the address from the toc entry.

If the symbol is defined, non-preemptable, and addressable with a 32-bit
signed offset from the toc pointer, the address can be computed
directly. e.g.

    addis 3, 2, .LC0@toc@ha  # R_PPC64_TOC16_HA
    ld    3, .LC0@toc@l(3)   # R_PPC64_TOC16_LO_DS, load the address from a .toc entry
    ld/lwa 3, 0(3)           # load the value from the address

    .section .toc,"aw",@progbits
    .LC0: .tc var[TC],var

can be relaxed to

    addis 3,2,var@toc@ha     # this may be relaxed to a nop,
    addi  3,3,var@toc@l      # then this becomes addi 3,2,var@toc
    ld/lwa 3, 0(3)           # load the value from the address

We can delete the test ppc64-got-indirect.s as its purpose is covered by
newly added ppc64-toc-relax.s and ppc64-toc-relax-constants.s

Reviewed By: ruiu, sfertile

Differential Revision: https://reviews.llvm.org/D60958

llvm-svn: 360112

1 files changed, 6 insertions, 1 deletions

diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index eb67592c0c3..85c8ffeb7ea 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -631,6 +631,7 @@ static uint64_t getRelocTargetVA(const InputFile *File, RelType Type, int64_t A,
   case R_GOTPLTONLY_PC:
     return In.GotPlt->getVA() + A - P;
   case R_GOTREL:
+  case R_PPC64_RELAX_TOC:
     return Sym.getVA(A) - In.Got->getVA();
   case R_GOTPLTREL:
     return Sym.getVA(A) - In.GotPlt->getVA();
@@ -894,7 +895,11 @@ void InputSectionBase::relocateAlloc(uint8_t *Buf, uint8_t *BufEnd) {
     switch (Expr) {
     case R_RELAX_GOT_PC:
     case R_RELAX_GOT_PC_NOPIC:
-      Target->relaxGot(BufLoc, TargetVA);
+      Target->relaxGot(BufLoc, Type, TargetVA);
+      break;
+    case R_PPC64_RELAX_TOC:
+      if (!tryRelaxPPC64TocIndirection(Type, Rel, BufLoc))
+        Target->relocateOne(BufLoc, Type, TargetVA);
       break;
     case R_RELAX_TLS_IE_TO_LE:
       Target->relaxTlsIeToLe(BufLoc, Type, TargetVA);