--- geos-3.8.1/include/geos/algorithm/ttmath/ttmathtypes.h.orig	2019-09-18 23:38:19.000000000 +0200
+++ geos-3.8.1/include/geos/algorithm/ttmath/ttmathtypes.h	2020-11-08 20:39:00.133786117 +0100
@@ -109,7 +109,7 @@
 */
 #if !defined TTMATH_PLATFORM32 && !defined TTMATH_PLATFORM64
 
-	#if !defined _M_X64 && !defined __x86_64__
+	#if !defined _M_X64 && !defined __x86_64__ || defined __ILP32__
 
 		/*
 			other platforms than x86 and amd64 are not recognized at the moment
--- geos-3.8.1/include/geos/algorithm/ttmath/ttmathuint_x86.h.orig	2019-09-18 23:38:19.000000000 +0200
+++ geos-3.8.1/include/geos/algorithm/ttmath/ttmathuint_x86.h	2020-11-08 21:56:34.060500817 +0100
@@ -524,7 +524,11 @@
 		uint dummy1, dummy2, dummy3;
 
 			__asm__ __volatile__(
+#ifdef __x86_64__
+				"push %%rdx							\n"
+#else
 				"push %%edx							\n"
+#endif
 				"xor %%edx, %%edx					\n"   // edx = 0, cf = 0
 			"1:										\n"
 				"mov (%%esi,%%edx,4), %%eax			\n"
@@ -536,7 +540,11 @@
 			"jnz 1b									\n"
 
 				"adc %%ecx, %%ecx					\n"   // ecx has the cf state
+#ifdef __x86_64__
+				"pop %%rax							\n"   // eax = rest
+#else
 				"pop %%eax							\n"   // eax = rest
+#endif
 
 				"or %%eax, %%eax					\n"
 				"jz 3f								\n"
@@ -857,7 +865,11 @@
 		uint dummy1, dummy2, dummy3;
 
 			__asm__ __volatile__(
+#ifdef __x86_64__
+				"push %%rdx							\n"
+#else
 				"push %%edx							\n"
+#endif
 				"xor %%edx, %%edx					\n"   // edx = 0, cf = 0
 			"1:										\n"
 				"mov (%%esi,%%edx,4), %%eax			\n"
@@ -869,7 +881,11 @@
 			"jnz 1b									\n"
 
 				"adc %%ecx, %%ecx					\n"   // ecx has the cf state
+#ifdef __x86_64__
+				"pop %%rax							\n"   // eax = rest
+#else
 				"pop %%eax							\n"   // eax = rest
+#endif
 
 				"or %%eax, %%eax					\n"
 				"jz 3f								\n"
@@ -1141,7 +1157,11 @@
 
 		__asm__  __volatile__(
 
+#ifdef __x86_64__
+			"push %%rbp						\n"
+#else
 			"push %%ebp						\n"
+#endif
 			
 			"movl %%ecx, %%esi				\n"
 			"movl $32, %%ecx				\n"
@@ -1171,7 +1191,11 @@
 			
 			"and $1, %%eax					\n"
 
+#ifdef __x86_64__
+			"pop %%rbp						\n"
+#else
 			"pop %%ebp						\n"
+#endif
 
 			: "=a" (c), "=D" (dummy), "=S" (dummy2), "=d" (dummy3)
 			: "0" (c),  "1" (b), "b" (p1), "c" (bits)
@@ -1272,7 +1296,11 @@
 
 			__asm__  __volatile__(
 
+#ifdef __x86_64__
+			"push %%rbp						\n"
+#else
 			"push %%ebp						\n"
+#endif
 			
 			"movl %%ecx, %%esi				\n"
 			"movl $32, %%ecx				\n"
@@ -1305,7 +1333,11 @@
 			"roll $1, %%eax					\n"
 			"andl $1, %%eax					\n"
 
+#ifdef __x86_64__
+			"pop %%rbp						\n"
+#else
 			"pop %%ebp						\n"
+#endif
 
 			: "=a" (c), "=D" (dummy), "=S" (dummy2), "=d" (dummy3)
 			: "0" (c),  "1" (b), "b" (p1), "c" (bits)