[AArch64] Return the correct size for TLSDESC_CALLSEQ

The branch relaxation pass is computing the wrong offsets because it assumes
TLSDESC_CALLSEQ eats up 4 bytes, when in fact it is lowered to an instruction
sequence taking up 16 bytes. This can become a problem in huge files with lots
of TLS accesses, as it may slowly move branch targets out of the range computed
by the branch relaxation pass.

Fixes PR24234 https://llvm.org/bugs/show_bug.cgi?id=24234

Differential Revision: https://reviews.llvm.org/D22870

llvm-svn: 277331

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
index e512cb89dac..319ee3b495c 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
@@ -56,6 +56,9 @@ unsigned AArch64InstrInfo::getInstSizeInBytes(const MachineInstr &MI) const {
   case TargetOpcode::IMPLICIT_DEF:
   case TargetOpcode::KILL:
     return 0;
+  case AArch64::TLSDESC_CALLSEQ:
+    // This gets lowered to an instruction sequence which takes 16 bytes
+    return 16;
   }
 
   llvm_unreachable("getInstSizeInBytes()- Unable to determin insn size");