From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tobias Bussmann <t.bussmann@gmx.net>
cc: John Naylor <johncnaylorls@gmail.com>, Lukas Fittl <lukas@fittl.com>,
        Jakob Egger <jakob@eggerapps.at>,
        pgsql-hackers <pgsql-hackers@postgresql.org>,
        Andres Freund <andres@anarazel.de>,
        Sandeep Thakkar <sandeep.thakkar@enterprisedb.com>
Subject: Re: Broken build on macOS (Universal / Intel): cpuid instruction not
 available
In-reply-to: <2927612.1780413646@sss.pgh.pa.us>
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Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Tue, 02 Jun 2026 11:20:46 -0400"
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Date: Tue, 02 Jun 2026 13:38:00 -0400
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I wrote:
> It seems there are two problems:

> 1. pg_cpu.h believes that x86-specific code can be conditional on
> #if defined(USE_SSE2) || defined(__i386__)
> but macOS doesn't define __i386__, only __x86_64__.  It works
> anyway on single-arch builds because the test to set USE_SSE2
> succeeds, but not on multi-arch builds.

> 2. checksum.c believes that it's okay to call x86_feature_available
> if USE_AVX2_WITH_RUNTIME_CHECK is set.

After further study, I found that USE_SSE2 is set like this in c.h:

#if (defined(__x86_64__) || defined(_M_AMD64))
#define USE_SSE2
...

So my interpretation of what was happening in pg_cpu.h was wrong.
I think we ought to s/USE_SSE2/__x86_64__/ there just to make this
less confusing, but the part of my quick-hack patch that touched
pg_cpu.h was really a no-op.

Also, the reason we manage to set USE_AVX2_WITH_RUNTIME_CHECK
in a multi-arch build is that what configure actually tests
is (a) is $host_cpu x86_64 and (b) does the compiler accept
__attribute__((target("avx2"))).  On a multi-arch build,
the ARM side spits out a warning
  '+avx2' is not a recognized feature for this target (ignoring feature)
but it doesn't actually fail, so configure thinks that's a success.

I think that a cleaner solution to this is to fix pg_cpu.h so
that x86_feature_available() exists but returns constant false
on non-x86 platforms.  A proposed patch for that is attached.

If we just do that much, a multi-arch macOS build produces the "not a
recognized feature" warning while compiling checksum.c, but it works.
Given that the build also produces all those ranlib warnings, I don't
know that suppressing "not a recognized feature" is worth worrying
about.  But if we want to, something similar to the checksum.c change
I posted before would do it.

			regards, tom lane

PS: does c.h's check for _M_AMD64 really do anything?  If we need
it there, why not in all the other places that check __x86_64__?


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Content-Description: cleanup-x86-tests-1.patch

diff --git a/src/include/port/pg_cpu.h b/src/include/port/pg_cpu.h
index 566ed7a16e3..5b25747e43a 100644
--- a/src/include/port/pg_cpu.h
+++ b/src/include/port/pg_cpu.h
@@ -13,8 +13,6 @@
 #ifndef PG_CPU_H
 #define PG_CPU_H
 
-#if defined(USE_SSE2) || defined(__i386__)
-
 typedef enum X86FeatureId
 {
 	/* Have we run feature detection? */
@@ -43,6 +41,8 @@ typedef enum X86FeatureId
 } X86FeatureId;
 #define X86FeaturesSize (PG_TSC_ADJUST + 1)
 
+#if defined(__x86_64__) || defined(__i386__)
+
 extern PGDLLIMPORT bool X86Features[];
 
 extern void set_x86_features(void);
@@ -58,6 +58,14 @@ x86_feature_available(X86FeatureId feature)
 
 extern uint32 x86_tsc_frequency_khz(char *source, size_t source_size);
 
-#endif							/* defined(USE_SSE2) || defined(__i386__) */
+#else							/* !(defined(__x86_64__)||defined(__i386__)) */
+
+static inline bool
+x86_feature_available(X86FeatureId feature)
+{
+	return false;
+}
+
+#endif							/* defined(__x86_64__) || defined(__i386__) */
 
 #endif							/* PG_CPU_H */
diff --git a/src/port/pg_cpu_x86.c b/src/port/pg_cpu_x86.c
index 0405ba19f6f..b050677f717 100644
--- a/src/port/pg_cpu_x86.c
+++ b/src/port/pg_cpu_x86.c
@@ -19,7 +19,7 @@
 #include "postgres_fe.h"
 #endif
 
-#if defined(USE_SSE2) || defined(__i386__)
+#if defined(__x86_64__) || defined(__i386__)
 
 #ifdef _MSC_VER
 #include <intrin.h>
@@ -287,10 +287,10 @@ x86_hypervisor_tsc_frequency_khz(void)
 	return 0;
 }
 
-#else							/* defined(USE_SSE2) || defined(__i386__) */
+#else							/* defined(__x86_64__) || defined(__i386__) */
 
 /* prevent linker complaints about empty module */
 extern int	pg_cpu_x86_dummy_variable;
 int			pg_cpu_x86_dummy_variable = 0;
 
-#endif							/* ! (USE_SSE2 || __i386__) */
+#endif							/* ! (__x86_64__ || __i386__) */

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