[clang][driver] Set TLSDESC as the default for Android on RISC-V

[ilovepi]

No description provided.

[pirama-arumuga-nainar]

Can you add a test similar to clang/test/Driver/emulated-tls.cpp?

[ilovepi]

Can you add a test similar to clang/test/Driver/emulated-tls.cpp?

I knew I was forgetting something when I threw this up. Thank you!

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-driver

Author: Paul Kirth (ilovepi)

Changes

Sets TLSDESC as the default on Android versions newer than 29, or if its
Android on RISC-V.

---

Full diff: https://github.com/llvm/llvm-project/pull/81198.diff

2 Files Affected:

• (modified) clang/test/Driver/tls-dialect.c (+5)
• (modified) llvm/include/llvm/TargetParser/Triple.h (+1-2)

diff --git a/clang/test/Driver/tls-dialect.c b/clang/test/Driver/tls-dialect.c
index 4e105ce3cea5d9..f309f4a44fbc3f 100644
--- a/clang/test/Driver/tls-dialect.c
+++ b/clang/test/Driver/tls-dialect.c
@@ -3,6 +3,11 @@
 // 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
 
+/// Android supports TLSDESC by default after Android version 29 and all RISC-V
+/// TLSDESC is not on by default in Linux, even on RISC-V
+// RUN: %clang -### --target=riscv64-android %s 2>&1 | FileCheck --check-prefix=DESC %s
+// RUN: %clang -### --target=riscv64-linux %s 2>&1 | FileCheck --check-prefix=NODESC %s
+
 /// LTO
 // RUN: %clang -### --target=riscv64-linux -flto -mtls-dialect=desc %s 2>&1 | FileCheck --check-prefix=LTO-DESC %s
 // RUN: %clang -### --target=riscv64-linux -flto %s 2>&1 | FileCheck --check-prefix=LTO-NODESC %s
diff --git a/llvm/include/llvm/TargetParser/Triple.h b/llvm/include/llvm/TargetParser/Triple.h
index 98d8490cc9f7a2..0382d97d3fe38b 100644
--- a/llvm/include/llvm/TargetParser/Triple.h
+++ b/llvm/include/llvm/TargetParser/Triple.h
@@ -1036,8 +1036,7 @@ class Triple {
   /// True if the target supports both general-dynamic and TLSDESC, and TLSDESC
   /// is enabled by default.
   bool hasDefaultTLSDESC() const {
-    // TODO: Improve check for other platforms, like Android, and RISC-V
-    return false;
+    return isAndroid() && (!isAndroidVersionLT(29) || isRISCV64());
   }
 
   /// Tests whether the target uses -data-sections as default.

[pirama-arumuga-nainar]

LGTM but let's wait for any comments from enh and maskray as well.

[enh-google]

i think my suggestion would be instead of

    return isAndroid() && (!isAndroidVersionLT(29) || isRISCV64());

just go with

    return isAndroid() && isRISCV64();

that solves today's problem, and we can worry about arm64 later[1]. (and x86-64 if/when that's implemented. and 32-bit never.)

---

1. why, when arm64 tlsdesc already shipped, and rv64 hasn't shipped yet? for exactly that reason :-) with rv64 i don't even have to [have rprichard] think about app compat issues, say, or [have danalbert] think about communicating the change to ndk users, etc...

[ilovepi]

Sounds good. I’ll update this when I have a chance tomorrow.

[MaskRay]

LGTM once the !isAndroidVersionLT(29) check is removed.

[MaskRay]

Delete riscv64-linux check. It's redundant.

[ilovepi]

That's a good point. I went ahead and updated the comment to point that out.