commit 6140cf9c51a5b636b25af28571e3086595ed47c8
author Brian Osman <brianosman@google.com> Mon May 15 15:34:46 2023 +0000
committer SkCQ <skcq-be@skia-corp.google.com.iam.gserviceaccount.com> Mon May 15 17:22:52 2023 +0000
tree 5f5433e10282fc2829d2f961d5afe7f400fb7b67
parent ef8a6f99efd79b1dffcdf89c9b42234852cb7a64

Fix detection of NEON f16 intrinsic availability on GCC

Bug: skia:12061
Bug: skia:14303
Change-Id: I17f855fbf85a21772c3ff650c1411e81d6088aeb
Reviewed-on: https://skia-review.googlesource.com/c/skcms/+/698184
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

src/Transform_inl.h

diff --git a/src/Transform_inl.h b/src/Transform_inl.h
index 17324b2..ede3732 100644
--- a/src/Transform_inl.h
+++ b/src/Transform_inl.h
@@ -51,8 +51,19 @@
 // This is more for organizational clarity... skcms.cc doesn't force these.
 #if N > 1 && defined(__ARM_NEON)
     #define USING_NEON
-    #if __ARM_FP & 2
-        #define USING_NEON_F16C
+
+    // We have to use two different mechanisms to enable the f16 conversion intrinsics:
+    #if defined(__clang__)
+        // Clang's arm_neon.h guards them with the FP hardware bit:
+        #if __ARM_FP & 2
+            #define USING_NEON_F16C
+        #endif
+    #elif defined(__GNUC__)
+        // GCC's arm_neon.h guards them with the FP16 format macros (IEEE and ALTERNATIVE).
+        // We don't actually want the alternative format - we're reading/writing IEEE f16 values.
+        #if defined(__ARM_FP16_FORMAT_IEEE)
+            #define USING_NEON_F16C
+        #endif
     #endif
 #endif