From cc2dbb8ea5329b509d79eedb6c0cbb9a1903b5ad Mon Sep 17 00:00:00 2001
From: WANG Xuerui <git@xen0n.name>
Date: Sat, 10 Aug 2024 18:38:47 +0800
Subject: [PATCH] meson: Additionally probe -mtls-dialect=desc for TLSDESC
 support

Previously only `-mtls-dialect=gnu2` was probed, which was appropriate
for arm, x86 and x86_64, but not for newer architectures such as
aarch64, loongarch64 and riscv64 which all use `-mtls-dialect=desc`
instead. Because the driver option is not consistent across
architectures (and probably will not), try both variants and choose the
first one working.

While at it, rename "gnu2_*" variables to "tlsdesc_*" respectively, for
clarity.

Cc: mesa-stable
Reviewed-by: Icenowy Zheng <uwu@icenowy.me>
Reviewed-by: Yukari Chiba <i@0x7f.cc>
Reviewed-by: David Heidelberg <david@ixit.cz>
Signed-off-by: WANG Xuerui <git@xen0n.name>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30599>
---
 meson.build | 38 ++++++++++++++++++++++----------------
 1 file changed, 22 insertions(+), 16 deletions(-)

diff --git a/meson.build b/meson.build
index f716a9e8179..3d72bb56f25 100644
--- a/meson.build
+++ b/meson.build
@@ -502,22 +502,28 @@ if not have_mtls_dialect
   if meson.is_cross_build() and not meson.can_run_host_binaries()
     warning('cannot auto-detect -mtls-dialect when cross-compiling, using compiler default')
   else
-    # -fpic to force dynamic tls, otherwise TLS relaxation defeats check
-    gnu2_test = cc.run('int __thread x; int main() { return x; }',
-                       args: ['-mtls-dialect=gnu2', '-fpic'],
-                       name: '-mtls-dialect=gnu2')
-    if gnu2_test.returncode() == 0 and (
-          # check for lld 13 bug: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5665
-          host_machine.cpu_family() != 'x86_64' or
-          # get_linker_id misses LDFLAGS=-fuse-ld=lld: https://github.com/mesonbuild/meson/issues/6377
-          #cc.get_linker_id() != 'ld.lld' or
-          cc.links('''int __thread x; int y; int main() { __asm__(
-                "leaq x@TLSDESC(%rip), %rax\n"
-                "movq y@GOTPCREL(%rip), %rdx\n"
-                "call *x@TLSCALL(%rax)\n"); }''', name: 'split TLSDESC')
-          )
-      c_cpp_args += '-mtls-dialect=gnu2'
-    endif
+    # The way to specify the TLSDESC dialect is architecture-specific.
+    # We probe both because there is not a fallback guaranteed to work for all
+    # future architectures.
+    foreach tlsdesc_arg : ['-mtls-dialect=gnu2', '-mtls-dialect=desc']
+      # -fpic to force dynamic tls, otherwise TLS relaxation defeats check
+      tlsdesc_test = cc.run('int __thread x; int main() { return x; }',
+                            args: [tlsdesc_arg, '-fpic'],
+                            name: tlsdesc_arg)
+      if tlsdesc_test.returncode() == 0 and (
+            # check for lld 13 bug: https://gitlab.freedesktop.org/mesa/mesa/-/issues/5665
+            host_machine.cpu_family() != 'x86_64' or
+            # get_linker_id misses LDFLAGS=-fuse-ld=lld: https://github.com/mesonbuild/meson/issues/6377
+            #cc.get_linker_id() != 'ld.lld' or
+            cc.links('''int __thread x; int y; int main() { __asm__(
+                  "leaq x@TLSDESC(%rip), %rax\n"
+                  "movq y@GOTPCREL(%rip), %rdx\n"
+                  "call *x@TLSCALL(%rax)\n"); }''', name: 'split TLSDESC')
+            )
+        c_cpp_args += tlsdesc_arg
+        break
+      endif
+    endforeach
   endif
 endif