$ ./configure --host=i686-pc-linux-gnu CFLAGS="-Og" CC="gcc -m32"
[...]
$ make
make[2]: Entering directory '/tmp/libgcrypt/libgcrypt-1.10.3/mpi'
/bin/sh ../libtool  --tag=CC   --mode=compile gcc -m32 -DHAVE_CONFIG_H -I. -I..  -I../src -I../src   -Og -fvisibility=hidden -fno-delete-null-pointer-checks -Wall -MT ec-nist.lo -MD -MP -MF .deps/ec-nist.Tpo -c -o ec-nist.lo ec-nist.c
libtool: compile:  gcc -m32 -DHAVE_CONFIG_H -I. -I.. -I../src -I../src -Og -fvisibility=hidden -fno-delete-null-pointer-checks -Wall -MT ec-nist.lo -MD -MP -MF .deps/ec-nist.Tpo -c ec-nist.c  -fPIC -DPIC -o .libs/ec-nist.o
In file included from ec-nist.c:34:
ec-nist.c: In function '_gcry_mpi_ec_nist256_mod':
ec-inline.h:701:3: error: 'asm' operand has impossible constraints or there are not enough registers
  701 |   __asm__ ("subl %11, %3\n" \
      |   ^~~~~~~
ec-inline.h:894:9: note: in expansion of macro 'SUB4_LIMB32'
  894 |         SUB4_LIMB32(A1.hi, A1.lo, A0.hi, A0.lo, \
      |         ^~~~~~~~~~~
ec-inline.h:1009:5: note: in expansion of macro 'SUB2_LIMB64'
 1009 |     SUB2_LIMB64(A4, A3, B4, B3, C4, C3); \
      |     ^~~~~~~~~~~
ec-nist.c:474:3: note: in expansion of macro 'SUB5_LIMB64'
  474 |   SUB5_LIMB64 (s[4], s[3], s[2], s[1], s[0],
      |   ^~~~~~~~~~~
make[2]: *** [Makefile:658: ec-nist.lo] Error 1
make[2]: Leaving directory '/tmp/libgcrypt/libgcrypt-1.10.3/mpi'