diff --git a/src/common/d2s.c b/src/common/d2s.c
index 34e7cd33bf9..0a9cb83fc49 100644
--- a/src/common/d2s.c
+++ b/src/common/d2s.c
@@ -53,7 +53,7 @@
  * alignment concerns that apply elsewhere.
  */
 #if !defined(HAVE_INT128) && defined(_MSC_VER) \
-	&& !defined(RYU_ONLY_64_BIT_OPS) && defined(_M_X64)
+	&& !defined(RYU_ONLY_64_BIT_OPS) && defined(__x86_64__)
 #define HAS_64_BIT_INTRINSICS
 #endif
 
diff --git a/src/include/c.h b/src/include/c.h
index f32989a6331..ef4dc5d1e63 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -106,6 +106,62 @@ extern "C++"
  * ----------------------------------------------------------------
  */
 
+/*
+ * Not all compilers follow gcc's names of macros for particular target
+ * architectures.  Let's standardize on gcc's names (with trailing __),
+ * and cause those to become defined here if they are not already.
+ *
+ * Note: while this list is alphabetical, it's necessary to check _M_ARM64
+ * before _M_AMD64, because Microsoft's ARM64EC environment defines both.
+ */
+#if defined(__arm__) || defined(__arm)
+#ifndef __arm__
+#define __arm__ 1
+#endif
+#elif defined(__aarch64__) || defined(_M_ARM64)
+#ifndef __aarch64__
+#define __aarch64__ 1
+#endif
+#elif defined(__loongarch64__) || defined(__loongarch64)
+#ifndef __loongarch64__
+#define __loongarch64__ 1
+#endif
+#elif defined(__mips__)
+/* no work */
+#elif defined(__mips64__)
+/* no work */
+#elif defined(__powerpc__) || defined(__ppc__)
+#ifndef __powerpc__
+#define __powerpc__ 1
+#endif
+#elif defined(__powerpc64__) || defined(__ppc64__)
+#ifndef __powerpc64__
+#define __powerpc64__ 1
+#endif
+#elif defined(__riscv__)
+/* no work */
+#elif defined(__riscv64__)
+/* no work */
+#elif defined(__s390__)
+/* no work */
+#elif defined(__s390x__)
+/* no work */
+#elif defined(__sparc__) || defined(__sparc)
+#ifndef __sparc__
+#define __sparc__ 1
+#endif
+#elif defined(__i386__) || defined (__i386) || defined(_M_IX86)
+#ifndef __i386__
+#define __i386__ 1
+#endif
+#elif defined(__x86_64__) || defined(__x86_64) || defined (__amd64) || defined(_M_AMD64)
+#ifndef __x86_64__
+#define __x86_64__ 1
+#endif
+#else
+#error "cannot identify target architecture"
+#endif
+
 /*
  * Disable "inline" if PG_FORCE_DISABLE_INLINE is defined.
  * This is used to work around compiler bugs and might also be useful for
@@ -1337,7 +1393,7 @@ typedef struct PGAlignedXLogBlock PGAlignedXLogBlock;
  * SSE2 instructions are part of the spec for the 64-bit x86 ISA. We assume
  * that compilers targeting this architecture understand SSE2 intrinsics.
  */
-#if (defined(__x86_64__) || defined(_M_AMD64))
+#if defined(__x86_64__)
 #define USE_SSE2
 
 #else							/* ! x86_64 */
diff --git a/src/include/port/atomics.h b/src/include/port/atomics.h
index c50d95d29e2..a605ea81d07 100644
--- a/src/include/port/atomics.h
+++ b/src/include/port/atomics.h
@@ -63,11 +63,11 @@
  * compiler barrier.
  *
  */
-#if defined(__arm__) || defined(__arm) || defined(__aarch64__)
+#if defined(__arm__) || defined(__aarch64__)
 #include "port/atomics/arch-arm.h"
-#elif defined(__i386__) || defined(__i386) || defined(__x86_64__)
+#elif defined(__i386__) || defined(__x86_64__)
 #include "port/atomics/arch-x86.h"
-#elif defined(__ppc__) || defined(__powerpc__) || defined(__ppc64__) || defined(__powerpc64__)
+#elif defined(__powerpc__) || defined(__powerpc64__)
 #include "port/atomics/arch-ppc.h"
 #endif
 
diff --git a/src/include/port/atomics/arch-x86.h b/src/include/port/atomics/arch-x86.h
index 88bba0e5f5c..231831dcf59 100644
--- a/src/include/port/atomics/arch-x86.h
+++ b/src/include/port/atomics/arch-x86.h
@@ -32,7 +32,7 @@
  */
 
 #if defined(__GNUC__) || defined(__INTEL_COMPILER)
-#if defined(__i386__) || defined(__i386)
+#if defined(__i386__)
 #define pg_memory_barrier_impl()		\
 	__asm__ __volatile__ ("lock; addl $0,0(%%esp)" : : : "memory", "cc")
 #elif defined(__x86_64__)
@@ -184,6 +184,6 @@ pg_atomic_fetch_add_u64_impl(volatile pg_atomic_uint64 *ptr, int64 add_)
 /*
  * 8 byte reads / writes have single-copy atomicity on all x86-64 cpus.
  */
-#if defined(__x86_64__) || defined(__x86_64) || defined(_M_X64) /* gcc, msvc */
+#if defined(__x86_64__)
 #define PG_HAVE_8BYTE_SINGLE_COPY_ATOMICITY
 #endif /* 8 byte single-copy atomicity */
diff --git a/src/include/port/pg_bitutils.h b/src/include/port/pg_bitutils.h
index 7a00d197013..2864ba431db 100644
--- a/src/include/port/pg_bitutils.h
+++ b/src/include/port/pg_bitutils.h
@@ -82,7 +82,7 @@ pg_leftmost_one_pos64(uint64 word)
 #error "cannot find integer type of the same size as uint64_t"
 #endif
 
-#elif defined(_MSC_VER) && (defined(_M_AMD64) || defined(_M_ARM64))
+#elif defined(_MSC_VER) && (defined(__x86_64__) || defined(__aarch64__))
 	unsigned long result;
 	bool		non_zero;
 
@@ -155,7 +155,7 @@ pg_rightmost_one_pos64(uint64 word)
 #error "cannot find integer type of the same size as uint64_t"
 #endif
 
-#elif defined(_MSC_VER) && (defined(_M_AMD64) || defined(_M_ARM64))
+#elif defined(_MSC_VER) && (defined(__x86_64__) || defined(__aarch64__))
 	unsigned long result;
 	bool		non_zero;
 
diff --git a/src/include/port/pg_cpu.h b/src/include/port/pg_cpu.h
index 566ed7a16e3..22aaa1aa5bc 100644
--- a/src/include/port/pg_cpu.h
+++ b/src/include/port/pg_cpu.h
@@ -13,7 +13,7 @@
 #ifndef PG_CPU_H
 #define PG_CPU_H
 
-#if defined(USE_SSE2) || defined(__i386__)
+#if defined(__x86_64__) || defined(__i386__)
 
 typedef enum X86FeatureId
 {
@@ -58,6 +58,6 @@ x86_feature_available(X86FeatureId feature)
 
 extern uint32 x86_tsc_frequency_khz(char *source, size_t source_size);
 
-#endif							/* defined(USE_SSE2) || defined(__i386__) */
+#endif							/* defined(__x86_64__) || defined(__i386__) */
 
 #endif							/* PG_CPU_H */
diff --git a/src/include/portability/instr_time.h b/src/include/portability/instr_time.h
index 655f8737b6f..826cc202847 100644
--- a/src/include/portability/instr_time.h
+++ b/src/include/portability/instr_time.h
@@ -95,7 +95,7 @@ typedef struct instr_time
  * PG_INSTR_TSC_CLOCK controls whether the TSC clock source is compiled in, and
  * potentially used based on timing_tsc_enabled.
  */
-#if defined(__x86_64__) || defined(_M_X64)
+#if defined(__x86_64__)
 #define PG_INSTR_TICKS_TO_NS 1
 #define PG_INSTR_TSC_CLOCK 1
 #elif defined(WIN32)
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index c9e52511990..96fcaaac01e 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -247,7 +247,7 @@ spin_delay(void)
  * We use the int-width variant of the builtin because it works on more chips
  * than other widths.
  */
-#if defined(__arm__) || defined(__arm) || defined(__aarch64__)
+#if defined(__arm__) || defined(__aarch64__)
 #ifdef HAVE_GCC__SYNC_INT32_TAS
 #define HAS_TEST_AND_SET
 
@@ -287,7 +287,7 @@ spin_delay(void)
 
 #endif	 /* __aarch64__ */
 #endif	 /* HAVE_GCC__SYNC_INT32_TAS */
-#endif	 /* __arm__ || __arm || __aarch64__ */
+#endif	 /* __arm__ || __aarch64__ */
 
 
 /* S/390 and S/390x Linux (32- and 64-bit zSeries) */
@@ -391,7 +391,7 @@ do \
 
 
 /* PowerPC */
-#if defined(__ppc__) || defined(__powerpc__) || defined(__ppc64__) || defined(__powerpc64__)
+#if defined(__powerpc__) || defined(__powerpc64__)
 #define HAS_TEST_AND_SET
 
 typedef unsigned int slock_t;
@@ -602,7 +602,7 @@ typedef LONG slock_t;
 
 #define SPIN_DELAY() spin_delay()
 
-#ifdef _M_ARM64
+#ifdef __aarch64__
 static __forceinline void
 spin_delay(void)
 {
@@ -633,7 +633,7 @@ spin_delay(void)
 
 #include <intrin.h>
 
-#ifdef _M_ARM64
+#ifdef __aarch64__
 
 /* _ReadWriteBarrier() is insufficient on non-TSO architectures. */
 #pragma intrinsic(_InterlockedExchange)
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__) */