From 457c891775a7397bdb0376bb1031e6e027af1c48 Mon Sep 17 00:00:00 2001
From: Jan Wassenberg <janwas@google.com>
Date: Fri, 31 May 2024 08:29:56 -0700
Subject: [PATCH] remove HWY_HAS_INCLUDE - mishandled by clang

PiperOrigin-RevId: 639043353
---
 hwy/base.h                 | 14 ++++++++++++--
 hwy/detect_compiler_arch.h |  6 +-----
 hwy/detect_targets.h       | 11 +++++++----
 3 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/hwy/base.h b/hwy/base.h
index d4eed94fac..7b13b0dd6e 100644
--- a/hwy/base.h
+++ b/hwy/base.h
@@ -53,9 +53,19 @@
 
 #endif  // !HWY_IDE
 
-#ifndef HWY_HAVE_CXX20_THREE_WAY_COMPARE  // allow opt-out
+#ifndef HWY_HAVE_COMPARE_HEADER  // allow override
+#define HWY_HAVE_COMPARE_HEADER 0
+#if defined(__has_include)  // note: wrapper macro fails on Clang ~17
+#if __has_include(<compare>)
+#undef HWY_HAVE_COMPARE_HEADER
+#define HWY_HAVE_COMPARE_HEADER 1
+#endif  // __has_include
+#endif  // defined(__has_include)
+#endif  // HWY_HAVE_COMPARE_HEADER
+
+#ifndef HWY_HAVE_CXX20_THREE_WAY_COMPARE  // allow override
 #if !defined(HWY_NO_LIBCXX) && defined(__cpp_impl_three_way_comparison) && \
-    __cpp_impl_three_way_comparison >= 201907L && HWY_HAS_INCLUDE(<compare>)
+    __cpp_impl_three_way_comparison >= 201907L && HWY_HAVE_COMPARE_HEADER
 #include <compare>
 #define HWY_HAVE_CXX20_THREE_WAY_COMPARE 1
 #else
diff --git a/hwy/detect_compiler_arch.h b/hwy/detect_compiler_arch.h
index 262048d087..94b49cb728 100644
--- a/hwy/detect_compiler_arch.h
+++ b/hwy/detect_compiler_arch.h
@@ -166,11 +166,7 @@
 #define HWY_HAS_FEATURE(name) 0
 #endif
 
-#ifdef __has_include
-#define HWY_HAS_INCLUDE(header) __has_include(header)
-#else
-#define HWY_HAS_INCLUDE(header) 0
-#endif
+// NOTE: clang ~17 does not correctly handle wrapping __has_include in a macro.
 
 #if HWY_COMPILER_MSVC && defined(_MSVC_LANG) && _MSVC_LANG > __cplusplus
 #define HWY_CXX_LANG _MSVC_LANG
diff --git a/hwy/detect_targets.h b/hwy/detect_targets.h
index c5aa009fad..db4c786489 100644
--- a/hwy/detect_targets.h
+++ b/hwy/detect_targets.h
@@ -577,19 +577,22 @@
 #endif
 // Defining one of HWY_COMPILE_ONLY_* will trump HWY_COMPILE_ALL_ATTAINABLE.
 
-// Allow opting out, and without a guarantee of success, opting-in.
-#ifndef HWY_HAVE_AUXV
+#ifndef HWY_HAVE_AUXV  // allow override
 #ifdef TOOLCHAIN_MISS_SYS_AUXV_H
 #define HWY_HAVE_AUXV 0  // CMake failed to find the header
 // glibc 2.16 added auxv, but checking for that requires features.h, and we do
 // not want to include system headers here. Instead check for the header
 // directly, which has been supported at least since GCC 5.4 and Clang 3.
+#elif defined(__has_include)  // note: wrapper macro fails on Clang ~17
 // clang-format off
-#elif HWY_HAS_INCLUDE(<sys/auxv.h>)
+#if __has_include(<sys/auxv.h>)
 // clang-format on
 #define HWY_HAVE_AUXV 1  // header present
 #else
-#define HWY_HAVE_AUXV 0  // header not present, or non Clang/GCC compiler
+#define HWY_HAVE_AUXV 0  // header not present
+#endif                   // __has_include
+#else                    // compiler lacks __has_include
+#define HWY_HAVE_AUXV 0
 #endif
 #endif  // HWY_HAVE_AUXV