Ensure USE_AVX... symbols are not defined if not building for x86_64.

Various code assumed this was true already, and usually it is.
However, it emerges that in a "universal" (multi-architecture)
macOS build, configure will define USE_AVX2_WITH_RUNTIME_CHECK
if the build host is x86_64, and then the arm64 half of the
build fails.

Ideally we'd get pg_config.h to define this symbol conditionally
depending on defined(__x86_64__), but I don't see any way to
persuade Autoconf to do that.  Instead, clean up the mess by
#undef'ing it again in c.h for not-x86_64 builds.

For consistency I made c.h also #undef the USE_AVX512... symbols.
Those are not actively broken, but it seems only happenstance
that configure's tests for them fail in a universal build.
Down the road we may have occasion to add more #undef's here.

This problem is new in v19, so no need for back-patch.

Reported-by: Sandeep Thakkar <sandeep.thakkar@enterprisedb.com>
Reported-by: Tobias Bussmann <t.bussmann@gmx.net>
Author: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/15574903-87C9-478A-B2D7-CC8F4C275DBB@gmx.net

diff --git a/src/include/c.h b/src/include/c.h
index 97ed8c63f5ea89d89759b9d6692fc1cf293e24ca..f32989a633105f1dbd93a1b7dd0309677a98a293 100644 (file)
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -1340,6 +1340,17 @@ typedef struct PGAlignedXLogBlock PGAlignedXLogBlock;
 #if (defined(__x86_64__) || defined(_M_AMD64))
 #define USE_SSE2
 
+#else                                                  /* ! x86_64 */
+
+/*
+ * In "universal" macOS builds, it's possible for AVX-related symbols to
+ * get defined if the build host is x86_64, but we mustn't try to build
+ * that code when cross-compiling to aarch64.
+ */
+#undef USE_AVX2_WITH_RUNTIME_CHECK
+#undef USE_AVX512_CRC32C_WITH_RUNTIME_CHECK
+#undef USE_AVX512_POPCNT_WITH_RUNTIME_CHECK
+
 /*
  * We use the Neon instructions if the compiler provides access to them (as
  * indicated by __ARM_NEON) and we are on aarch64.  While Neon support is
@@ -1348,9 +1359,10 @@ typedef struct PGAlignedXLogBlock PGAlignedXLogBlock;
  * could not realistically use it there without a run-time check, which seems
  * not worth the trouble for now.
  */
-#elif defined(__aarch64__) && defined(__ARM_NEON)
+#if defined(__aarch64__) && defined(__ARM_NEON)
 #define USE_NEON
 #endif
+#endif                                                 /* x86_64 */
 
 /* ----------------------------------------------------------------
  *                             Section 9: system-specific hacks