build: remove confusing and inconsistent disable-asm option

1. It didn't actually disable asm usage in our code. Regardless of the setting,
   asm is used in random.cpp and support/cleanse.cpp.
2. The value wasn't forwarded to libsecp as a user might have reasonably
   expected.
3. We now have the DISABLE_OPTIMIZED_SHA256 define which is what disable-asm
   actually did in practice.

If there is any desire, we can hook DISABLE_OPTIMIZED_SHA256 up to a new
configure option that actually does what it says.

configure.ac

@@ -249,16 +249,6 @@ AC_ARG_ENABLE([threadlocal],
   [use_thread_local=$enableval],
   [use_thread_local=auto])
 
-AC_ARG_ENABLE([asm],
-  [AS_HELP_STRING([--disable-asm],
-  [disable assembly routines (enabled by default)])],
-  [use_asm=$enableval],
-  [use_asm=yes])
-
-if test "$use_asm" = "yes"; then
-  AC_DEFINE([USE_ASM], [1], [Define this symbol to build in assembly routines])
-fi
-
 AC_ARG_ENABLE([zmq],
   [AS_HELP_STRING([--disable-zmq],
   [disable ZMQ notifications])],
@@ -460,8 +450,6 @@ enable_sse41=no
 enable_avx2=no
 enable_x86_shani=no
 
-if test "$use_asm" = "yes"; then
-
 dnl Check for optional instruction set support. Enabling these does _not_ imply that all code will
 dnl be compiled with them, rather that specific objects/libs may use them after checking for runtime
 dnl compatibility.
@@ -600,8 +588,6 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
 )
 CXXFLAGS="$TEMP_CXXFLAGS"
 
-fi
-
 CORE_CPPFLAGS="$CORE_CPPFLAGS -DHAVE_BUILD_INFO"
 
 AC_ARG_WITH([utils],
@@ -1817,7 +1803,6 @@ AM_CONDITIONAL([ENABLE_AVX2], [test "$enable_avx2" = "yes"])
 AM_CONDITIONAL([ENABLE_X86_SHANI], [test "$enable_x86_shani" = "yes"])
 AM_CONDITIONAL([ENABLE_ARM_CRC], [test "$enable_arm_crc" = "yes"])
 AM_CONDITIONAL([ENABLE_ARM_SHANI], [test "$enable_arm_shani" = "yes"])
-AM_CONDITIONAL([USE_ASM], [test "$use_asm" = "yes"])
 AM_CONDITIONAL([WORDS_BIGENDIAN], [test "$ac_cv_c_bigendian" = "yes"])
 AM_CONDITIONAL([USE_NATPMP], [test "$use_natpmp" = "yes"])
 AM_CONDITIONAL([USE_UPNP], [test "$use_upnp" = "yes"])
@@ -1972,7 +1957,6 @@ echo "  with fuzz binary = $enable_fuzz_binary"
 echo "  with bench      = $use_bench"
 echo "  with upnp       = $use_upnp"
 echo "  with natpmp     = $use_natpmp"
-echo "  use asm         = $use_asm"
 echo "  USDT tracing    = $use_usdt"
 echo "  sanitizers      = $use_sanitizers"
 echo "  debug enabled   = $enable_debug"

src/Makefile.am

@@ -50,10 +50,8 @@ LIBBITCOIN_WALLET_TOOL=libbitcoin_wallet_tool.a
 endif
 
 LIBBITCOIN_CRYPTO = $(LIBBITCOIN_CRYPTO_BASE)
-if USE_ASM
 LIBBITCOIN_CRYPTO_SSE4 = crypto/libbitcoin_crypto_sse4.la
 LIBBITCOIN_CRYPTO += $(LIBBITCOIN_CRYPTO_SSE4)
-endif
 if ENABLE_SSE41
 LIBBITCOIN_CRYPTO_SSE41 = crypto/libbitcoin_crypto_sse41.la
 LIBBITCOIN_CRYPTO += $(LIBBITCOIN_CRYPTO_SSE41)

src/crypto/sha256.cpp

@@ -26,13 +26,11 @@
 #endif
 
 #if defined(__x86_64__) || defined(__amd64__) || defined(__i386__)
-#if defined(USE_ASM)
 namespace sha256_sse4
 {
 void Transform(uint32_t* s, const unsigned char* chunk, size_t blocks);
 }
 #endif
-#endif
 
 namespace sha256d64_sse41
 {
@@ -574,7 +572,7 @@ bool SelfTest() {
 }
 
 #if !defined(DISABLE_OPTIMIZED_SHA256)
-#if defined(USE_ASM) && (defined(__x86_64__) || defined(__amd64__) || defined(__i386__))
+#if (defined(__x86_64__) || defined(__amd64__) || defined(__i386__))
 /** Check whether the OS has enabled AVX registers. */
 bool AVXEnabled()
 {
@@ -597,7 +595,7 @@ std::string SHA256AutoDetect(sha256_implementation::UseImplementation use_implem
     TransformD64_8way = nullptr;
 
 #if !defined(DISABLE_OPTIMIZED_SHA256)
-#if defined(USE_ASM) && defined(HAVE_GETCPUID)
+#if defined(HAVE_GETCPUID)
     bool have_sse4 = false;
     bool have_xsave = false;
     bool have_avx = false;
@@ -654,7 +652,7 @@ std::string SHA256AutoDetect(sha256_implementation::UseImplementation use_implem
         ret += ",avx2(8way)";
     }
 #endif
-#endif // defined(USE_ASM) && defined(HAVE_GETCPUID)
+#endif // defined(HAVE_GETCPUID)
 
 #if defined(ENABLE_ARM_SHANI)
     bool have_arm_shani = false;