aom: cpu.cmake: Do more elaborate test of whether SVE can be compiled (49b7d)

From 49b7dcd627a0c00f62b8db23320f382d296b4637 Mon Sep 17 00:00:00 2001
From: Martin Storsjo <[EMAIL REDACTED]>
Date: Wed, 1 May 2024 00:45:41 +0300
Subject: [PATCH] cpu.cmake: Do more elaborate test of whether SVE can be
 compiled

For Windows targets, Clang will successfully compile simpler
SVE functions, but if the function requires backing up and restoring
SVE registers (as part of the AAPCS calling convention), Clang
will fail to generate unwind data for this function, resulting
in an error.

This issue is tracked upstream in Clang in
https://github.com/llvm/llvm-project/issues/80009.

Check whether the compiler can compile such a function, and
disable SVE if it is unable to handle that case.

Change-Id: I307d7398cedd1942c39ef034431a51696264ff47
(cherry picked from commit 5ccdc66ab6eb8eb300eda854fab4ff250b2c2f92)
---
 build/cmake/cpu.cmake | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/build/cmake/cpu.cmake b/build/cmake/cpu.cmake
index bd13d035d..776f6af69 100644
--- a/build/cmake/cpu.cmake
+++ b/build/cmake/cpu.cmake
@@ -55,8 +55,18 @@ if("${AOM_TARGET_CPU}" STREQUAL "arm64")
 #endif
 #include <arm_sve.h>
 #include <arm_neon_sve_bridge.h>" HAVE_SVE_HEADERS)
+    # Check whether the compiler can compile SVE functions that require
+    # backup/restore of SVE registers according to AAPCS. Clang for Windows used
+    # to fail this, see https://github.com/llvm/llvm-project/issues/80009.
+    aom_check_source_compiles("arm_sve_preserve" "
+#include <arm_sve.h>
+void other(void);
+svfloat32_t func(svfloat32_t a) {
+  other();
+  return a;
+}" CAN_COMPILE_SVE)
     set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQURED_FLAGS})
-    if(HAVE_SVE_HEADERS EQUAL 0)
+    if(HAVE_SVE_HEADERS EQUAL 0 OR CAN_COMPILE_SVE EQUAL 0)
       set(ENABLE_SVE 0)
     endif()
   endif()