This option allows selecting the TLS size in the local exec TLS model,

which is the default TLS model for non-PIC objects. This allows large/
many thread local variables or a compact/fast code in an executable.

Specification is same as that of GCC. For example, the code model
option precedes the TLS size option.

TLS access models other than local-exec are not changed. It means
supoort of the large code model is only in the local exec TLS model.

Patch By KAWASHIMA Takahiro (kawashima-fj <t-kawashima@fujitsu.com>)
Reviewers: dmgreen, mstorsjo, t.p.northover, peter.smith, ostannard
Reviewd By: peter.smith
Committed by: peter.smith

Differential Revision: https://reviews.llvm.org/D71688

1 files changed, 11 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
index 68f4ee08048..6048010ee0c 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
@@ -288,6 +288,17 @@ AArch64TargetMachine::AArch64TargetMachine(const Target &T, const Triple &TT,
     this->Options.TrapUnreachable = true;
   }
 
+  if (this->Options.TLSSize == 0) // default
+    this->Options.TLSSize = 24;
+  if ((getCodeModel() == CodeModel::Small ||
+       getCodeModel() == CodeModel::Kernel) &&
+      this->Options.TLSSize > 32)
+    // for the small (and kernel) code model, the maximum TLS size is 4GiB
+    this->Options.TLSSize = 32;
+  else if (getCodeModel() == CodeModel::Tiny && this->Options.TLSSize > 24)
+    // for the tiny code model, the maximum TLS size is 1MiB (< 16MiB)
+    this->Options.TLSSize = 24;
+
   // Enable GlobalISel at or below EnableGlobalISelAt0, unless this is
   // MachO/CodeModel::Large, which GlobalISel does not support.
   if (getOptLevel() <= EnableGlobalISelAtO &&