[clang][x86] Support -mtls-dialect for x86_64 targets

[ilovepi]

This patch allows -mtls-dialect= to take desc, trad, gnu and
gnu2 options. desc and gnu2 can be used for TLSDESC code
generation, while trad and gnu maintain the existing TLS behavior.

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-driver

Author: Paul Kirth (ilovepi)

Changes

This patch allows -mtls-dialect= to take desc, trad, gnu and
gnu2 options. desc and gnu2 can be used for TLSDESC code
generation, while trad and gnu maintain the existing TLS behavior.

---

Full diff: https://github.com/llvm/llvm-project/pull/84086.diff

2 Files Affected:

• (modified) clang/lib/Driver/ToolChains/CommonArgs.cpp (+2-1)
• (modified) clang/test/Driver/tls-dialect.c (+1-1)

diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 7f0f78b41e79ed..b68773745cbcfc 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -740,7 +740,8 @@ bool tools::isTLSDESCEnabled(const ToolChain &TC,
     SupportedArgument = V == "desc" || V == "trad";
     EnableTLSDESC = V == "desc";
   } else if (Triple.isX86()) {
-    SupportedArgument = V == "gnu";
+    SupportedArgument = V == "desc" || V == "trad" || V == "gnu" || V == "gnu2";
+    EnableTLSDESC = V == "desc" || V == "gnu2";
   } else {
     Unsupported = true;
   }
diff --git a/clang/test/Driver/tls-dialect.c b/clang/test/Driver/tls-dialect.c
index f73915b28ec2a3..a808dd81531ce7 100644
--- a/clang/test/Driver/tls-dialect.c
+++ b/clang/test/Driver/tls-dialect.c
@@ -2,6 +2,7 @@
 // RUN: %clang -### --target=riscv64-linux -mtls-dialect=trad %s 2>&1 | FileCheck --check-prefix=NODESC %s
 // RUN: %clang -### --target=riscv64-linux %s 2>&1 | FileCheck --check-prefix=NODESC %s
 // RUN: %clang -### --target=x86_64-linux -mtls-dialect=gnu %s 2>&1 | FileCheck --check-prefix=NODESC %s
+// RUN: %clang -### --target=x86_64-linux -mtls-dialect=gnu2 %s 2>&1 | FileCheck --check-prefix=DESC %s
 
 /// Android supports TLSDESC by default on RISC-V
 /// TLSDESC is not on by default in Linux, even on RISC-V, and is covered above
@@ -18,7 +19,6 @@
 
 /// Unsupported argument
 // RUN: not %clang -### --target=riscv64-linux -mtls-dialect=gnu2 %s 2>&1 | FileCheck --check-prefix=UNSUPPORTED-ARG %s
-// RUN: not %clang -### --target=x86_64-linux -mtls-dialect=gnu2 %s 2>&1 | FileCheck --check-prefix=UNSUPPORTED-ARG %s
 
 // DESC:       "-cc1" {{.*}}"-enable-tlsdesc"
 // NODESC-NOT: "-enable-tlsdesc"