[SECP256K1] Remove num/gmp support

Summary:
```
The whole "num" API and its libgmp-based implementation are now unused.
Remove them.
```

Partial backport of [[bitcoin-core/secp256k1#831 | secp256k1#831]]:
bitcoin-core/secp256k1@1f233b3

Depends on D9407.

Test Plan:
  ninja all check-all

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Subscribers: majcosta

Differential Revision: https://reviews.bitcoinabc.org/D9408

.cirrus.yml

@@ -1,6 +1,5 @@
 env:
   WIDEMUL: auto
-  BIGNUM: gmp
   STATICPRECOMPUTATION: yes
   ECMULTGENPRECISION: auto
   ASM: no
@@ -49,9 +48,8 @@ task:
     - env: {WIDEMUL: int128,  RECOVERY: yes,            EXPERIMENTAL: yes,                SCHNORRSIG: yes}
     - env: {WIDEMUL: int128,                 ECDH: yes, EXPERIMENTAL: yes, MULTISET: yes, SCHNORRSIG: yes}
     - env: {WIDEMUL: int128,  ASM: x86_64}
-    - env: {BIGNUM: no}
-    - env: {BIGNUM: no,       RECOVERY: yes,            EXPERIMENTAL: yes, MULTISET: yes, SCHNORRSIG: yes}
-    - env: {BIGNUM: no,       STATICPRECOMPUTATION: no}
+    - env: {                  RECOVERY: yes,            EXPERIMENTAL: yes, MULTISET: yes, SCHNORRSIG: yes}
+    - env: {                  STATICPRECOMPUTATION: no}
     - env: {AUTOTOOLS_TARGET: distcheck, CMAKE_TARGET: install, WITH_VALGRIND: no, CTIMETEST: no, BENCH: no}
     - env: {AUTOTOOLS_EXTRA_FLAGS: CPPFLAGS=-DDETERMINISTIC, CMAKE_EXTRA_FLAGS: -DCMAKE_C_FLAGS=-DDETERMINISTIC}
     - env: {AUTOTOOLS_EXTRA_FLAGS: CFLAGS=-O0, CMAKE_EXTRA_FLAGS: -DCMAKE_BUILD_TYPE=Debug, CTIMETEST: no}
@@ -63,7 +61,6 @@ task:
         CFLAGS:  "-fsanitize=undefined -fno-omit-frame-pointer"
         LDFLAGS: "-fsanitize=undefined -fno-omit-frame-pointer"
         UBSAN_OPTIONS: "print_stacktrace=1:halt_on_error=1"
-        BIGNUM: no
         ASM: x86_64
         ECDH: yes
         RECOVERY: yes
@@ -75,7 +72,6 @@ task:
     - env: { ECMULTGENPRECISION: 8 }
     - env:
         RUN_VALGRIND: yes
-        BIGNUM: no
         ASM: x86_64
         ECDH: yes
         RECOVERY: yes
@@ -113,11 +109,6 @@ task:
         CC: i686-linux-gnu-gcc
     - env:
         CC: clang --target=i686-pc-linux-gnu -isystem /usr/i686-linux-gnu/include
-  matrix:
-    - env:
-        BIGNUM: gmp
-    - env:
-        BIGNUM: no
   test_script:
     - ./ci/build_autotools.sh
     - ./ci/build_cmake.sh
@@ -177,7 +168,7 @@ task:
     # If we haven't restored from cached (and just run brew install), this is a no-op.
     - brew link valgrind
   brew_script:
-    - brew install automake cmake gcc@9 gmp libtool ninja
+    - brew install automake cmake gcc@9 libtool ninja
   test_script:
     - ./ci/build_autotools.sh
     - ./ci/build_cmake.sh
@@ -193,7 +184,6 @@ task:
     QEMU_CMD: qemu-s390x
     HOST: s390x-linux-gnu
     WITH_VALGRIND: no
-    BIGNUM: no
     ECDH: yes
     RECOVERY: yes
     EXPERIMENTAL: yes

CMakeLists.txt

@@ -73,20 +73,6 @@ set(SECP256K1_PUBLIC_HEADERS
 	include/secp256k1_preallocated.h
 )
 
-option(SECP256K1_ENABLE_BIGNUM "Use the GMP bignum implementation" OFF)
-if(SECP256K1_ENABLE_BIGNUM)
-	# We need to link in GMP
-	find_package(GMP REQUIRED)
-	target_link_libraries(secp256k1 GMP::gmp)
-	set(USE_NUM_GMP 1)
-	set(USE_FIELD_INV_NUM 1)
-	set(USE_SCALAR_INV_NUM 1)
-else()
-	set(USE_NUM_NONE 1)
-	set(USE_FIELD_INV_BUILTIN 1)
-	set(USE_SCALAR_INV_BUILTIN 1)
-endif()
-
 # Guess the target architecture, within the ones with supported ASM.
 # First check if the CMAKE_C_COMPILER_TARGET is set (should be when
 # cross compiling), then CMAKE_SYSTEM_PROCESSOR as a fallback if meaningful

Makefile.am

@@ -18,8 +18,6 @@ noinst_HEADERS += src/scalar_8x32_impl.h
 noinst_HEADERS += src/scalar_low_impl.h
 noinst_HEADERS += src/group.h
 noinst_HEADERS += src/group_impl.h
-noinst_HEADERS += src/num_gmp.h
-noinst_HEADERS += src/num_gmp_impl.h
 noinst_HEADERS += src/ecdsa.h
 noinst_HEADERS += src/ecdsa_impl.h
 noinst_HEADERS += src/eckey.h
@@ -30,8 +28,6 @@ noinst_HEADERS += src/ecmult_const.h
 noinst_HEADERS += src/ecmult_const_impl.h
 noinst_HEADERS += src/ecmult_gen.h
 noinst_HEADERS += src/ecmult_gen_impl.h
-noinst_HEADERS += src/num.h
-noinst_HEADERS += src/num_impl.h
 noinst_HEADERS += src/field_10x26.h
 noinst_HEADERS += src/field_10x26_impl.h
 noinst_HEADERS += src/field_5x52.h

build-aux/m4/bitcoin_secp.m4

@@ -75,19 +75,6 @@ if test x"$has_libcrypto" = x"yes" && test x"$has_openssl_ec" = x; then
 fi
 ])
 
-dnl
-AC_DEFUN([SECP_GMP_CHECK],[
-if test x"$has_gmp" != x"yes"; then
-  CPPFLAGS_TEMP="$CPPFLAGS"
-  CPPFLAGS="$GMP_CPPFLAGS $CPPFLAGS"
-  LIBS_TEMP="$LIBS"
-  LIBS="$GMP_LIBS $LIBS"
-  AC_CHECK_HEADER(gmp.h,[AC_CHECK_LIB(gmp, __gmpz_init,[has_gmp=yes; GMP_LIBS="$GMP_LIBS -lgmp"; AC_DEFINE(HAVE_LIBGMP,1,[Define this symbol if libgmp is installed])])])
-  CPPFLAGS="$CPPFLAGS_TEMP"
-  LIBS="$LIBS_TEMP"
-fi
-])
-
 AC_DEFUN([SECP_VALGRIND_CHECK],[
 if test x"$has_valgrind" != x"yes"; then
   CPPFLAGS_TEMP="$CPPFLAGS"

ci/build_autotools.sh

@@ -34,7 +34,6 @@ pushd buildautotools
 ../configure \
   --enable-experimental=$EXPERIMENTAL \
   --with-test-override-wide-multiply=$WIDEMUL \
-  --with-bignum=$BIGNUM \
   --with-asm=$ASM \
   --enable-ecmult-static-precomputation=$STATICPRECOMPUTATION \
   --with-ecmult-gen-precision=$ECMULTGENPRECISION \

ci/build_cmake.sh

@@ -45,7 +45,6 @@ ${CMAKE_COMMAND} -GNinja .. \
   -DSECP256K1_ENABLE_MODULE_EXTRAKEYS=$SCHNORRSIG \
   -DSECP256K1_ENABLE_MODULE_SCHNORRSIG=$SCHNORRSIG \
   -DSECP256K1_ENABLE_JNI=$JNI \
-  -DSECP256K1_ENABLE_BIGNUM=$BIGNUM \
   -DSECP256K1_USE_ASM=$ASM \
   -DSECP256K1_TEST_OVERRIDE_WIDE_MULTIPLY=$WIDEMUL \
   $ECMULT_GEN_PRECISION_ARG \

ci/linux-debian.Dockerfile

@@ -8,7 +8,7 @@ RUN apt-get update
 # dkpg-dev: to make pkg-config work in cross-builds
 RUN apt-get install --no-install-recommends --no-upgrade -y \
         automake default-jdk dpkg-dev libssl-dev libtool make ninja-build pkg-config python3 qemu-user valgrind \
-        gcc clang libc6-dbg libgmp-dev \
-        gcc-i686-linux-gnu libc6-dev-i386-cross libc6-dbg:i386 libgmp-dev:i386 \
+        gcc clang libc6-dbg \
+        gcc-i686-linux-gnu libc6-dev-i386-cross libc6-dbg:i386 \
         gcc-s390x-linux-gnu libc6-dev-s390x-cross libc6-dbg:s390x
 RUN apt-get install -t buster-backports --no-install-recommends --no-upgrade -y cmake

configure.ac

@@ -48,17 +48,12 @@ case $host_os in
          # in expected paths because they may conflict with system files. Ask
          # Homebrew where each one is located, then adjust paths accordingly.
          openssl_prefix=`$BREW --prefix openssl 2>/dev/null`
-         gmp_prefix=`$BREW --prefix gmp 2>/dev/null`
          valgrind_prefix=`$BREW --prefix valgrind 2>/dev/null`
          if test x$openssl_prefix != x; then
            PKG_CONFIG_PATH="$openssl_prefix/lib/pkgconfig:$PKG_CONFIG_PATH"
            export PKG_CONFIG_PATH
            CRYPTO_CPPFLAGS="-I$openssl_prefix/include"
          fi
-         if test x$gmp_prefix != x; then
-           GMP_CPPFLAGS="-I$gmp_prefix/include"
-           GMP_LIBS="-L$gmp_prefix/lib"
-         fi
          if test x$valgrind_prefix != x; then
            VALGRIND_CPPFLAGS="-I$valgrind_prefix/include"
          fi
@@ -179,9 +174,6 @@ AC_ARG_ENABLE(jni,
     [use_jni=$enableval],
     [use_jni=no])
 
-AC_ARG_WITH([bignum], [AS_HELP_STRING([--with-bignum=gmp|no|auto],
-[bignum implementation to use [default=auto]])],[req_bignum=$withval], [req_bignum=auto])
-
 AC_ARG_WITH([asm], [AS_HELP_STRING([--with-asm=x86_64|arm|no|auto],
 [assembly optimizations to use (experimental: arm) [default=auto]])],[req_asm=$withval], [req_asm=auto])
 
@@ -260,32 +252,6 @@ else
   esac
 fi
 
-if test x"$req_bignum" = x"auto"; then
-  SECP_GMP_CHECK
-  if test x"$has_gmp" = x"yes"; then
-    set_bignum=gmp
-  fi
-
-  if test x"$set_bignum" = x; then
-    set_bignum=no
-  fi
-else
-  set_bignum=$req_bignum
-  case $set_bignum in
-  gmp)
-    SECP_GMP_CHECK
-    if test x"$has_gmp" != x"yes"; then
-      AC_MSG_ERROR([gmp bignum explicitly requested but libgmp not available])
-    fi
-    ;;
-  no)
-    ;;
-  *)
-    AC_MSG_ERROR([invalid bignum implementation selection])
-    ;;
-  esac
-fi
-
 # Select assembly optimization
 use_external_asm=no
 
@@ -323,24 +289,6 @@ auto)
   ;;
 esac
 
-# Select bignum implementation
-case $set_bignum in
-gmp)
-  AC_DEFINE(HAVE_LIBGMP, 1, [Define this symbol if libgmp is installed])
-  AC_DEFINE(USE_NUM_GMP, 1, [Define this symbol to use the gmp implementation for num])
-  AC_DEFINE(USE_FIELD_INV_NUM, 1, [Define this symbol to use the num-based field inverse implementation])
-  AC_DEFINE(USE_SCALAR_INV_NUM, 1, [Define this symbol to use the num-based scalar inverse implementation])
-  ;;
-no)
-  AC_DEFINE(USE_NUM_NONE, 1, [Define this symbol to use no num implementation])
-  AC_DEFINE(USE_FIELD_INV_BUILTIN, 1, [Define this symbol to use the native field inverse implementation])
-  AC_DEFINE(USE_SCALAR_INV_BUILTIN, 1, [Define this symbol to use the native scalar inverse implementation])
-  ;;
-*)
-  AC_MSG_ERROR([invalid bignum implementation])
-  ;;
-esac
-
 # Set ecmult window size
 if test x"$req_ecmult_window" = x"auto"; then
   set_ecmult_window=15
@@ -428,11 +376,6 @@ if test x"$use_jni" != x"no"; then
   fi
 fi
 
-if test x"$set_bignum" = x"gmp"; then
-  SECP_LIBS="$SECP_LIBS $GMP_LIBS"
-  SECP_INCLUDES="$SECP_INCLUDES $GMP_CPPFLAGS"
-fi
-
 if test x"$enable_valgrind" = x"yes"; then
   SECP_INCLUDES="$SECP_INCLUDES $VALGRIND_CPPFLAGS"
 fi
@@ -627,7 +570,6 @@ echo "  module extrakeys        = $enable_module_extrakeys"
 echo "  module schnorrsig       = $enable_module_schnorrsig"
 echo
 echo "  asm                     = $set_asm"
-echo "  bignum                  = $set_bignum"
 echo "  ecmult window size      = $set_ecmult_window"
 echo "  ecmult gen prec. bits   = $set_ecmult_gen_precision"
 # Hide test-only options unless they're used.

src/basic-config.h

@@ -13,19 +13,10 @@
 #undef USE_ECMULT_STATIC_PRECOMPUTATION
 #undef USE_EXTERNAL_ASM
 #undef USE_EXTERNAL_DEFAULT_CALLBACKS
-#undef USE_FIELD_INV_BUILTIN
-#undef USE_FIELD_INV_NUM
-#undef USE_NUM_GMP
-#undef USE_NUM_NONE
-#undef USE_SCALAR_INV_BUILTIN
-#undef USE_SCALAR_INV_NUM
 #undef USE_FORCE_WIDEMUL_INT64
 #undef USE_FORCE_WIDEMUL_INT128
 #undef ECMULT_WINDOW_SIZE
 
-#define USE_NUM_NONE 1
-#define USE_FIELD_INV_BUILTIN 1
-#define USE_SCALAR_INV_BUILTIN 1
 #define USE_WIDEMUL_64 1
 #define ECMULT_WINDOW_SIZE 15
 

src/bench_ecmult.c

@@ -9,7 +9,6 @@
 
 #include "util.h"
 #include "hash_impl.h"
-#include "num_impl.h"
 #include "field_impl.h"
 #include "group_impl.h"
 #include "scalar_impl.h"