[AArch64] Support selecting TPIDR_EL[1-3] as the thread base

Add an -mtp=el[0-3] option to select which of the AArch64 thread ID registers
will be used for the TLS base pointer.

This is a followup to rL356657 which added subtarget features to enable
accesses to the privileged thread ID registers.

Patch by Philip Derrin!

Differential revision: https://reviews.llvm.org/D59631

llvm-svn: 357250

1 files changed, 12 insertions, 0 deletions

diff --git a/clang/lib/Driver/ToolChains/Arch/AArch64.cpp b/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
index e229e4c13cf..35d11f4e2d3 100644
--- a/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
@@ -194,6 +194,18 @@ void aarch64::getAArch64TargetFeatures(const Driver &D,
     Features.push_back("-neon");
   }
 
+  if (Arg *A = Args.getLastArg(options::OPT_mtp_mode_EQ)) {
+    StringRef Mtp = A->getValue();
+    if (Mtp == "el3")
+      Features.push_back("+tpidr-el3");
+    else if (Mtp == "el2")
+      Features.push_back("+tpidr-el2");
+    else if (Mtp == "el1")
+      Features.push_back("+tpidr-el1");
+    else if (Mtp != "el0")
+      D.Diag(diag::err_drv_invalid_mtp) << A->getAsString(Args);
+  }
+
   // En/disable crc
   if (Arg *A = Args.getLastArg(options::OPT_mcrc, options::OPT_mnocrc)) {
     if (A->getOption().matches(options::OPT_mcrc))