Merge bitcoin#13393: Enable double-SHA256-for-64-byte code on 32-bit x86

57ba401 Enable double-SHA256-for-64-byte code on 32-bit x86 (Pieter Wuille)

Pull request description:

  The SSE4 and AVX2 double-SHA256-for-64-byte input code from bitcoin#13191 compiles fine on 32-bit x86 systems, but the autodetection logic in sha256.cpp doesn't enable it. Fix this.

  Note that these instruction sets are only available on CPUs that support 64-bit mode as well, so it is only beneficial in the (perhaps unlikely) scenario where a 64-bit CPU is running a 32-bit Bitcoin Core binary.

Tree-SHA512: 39d5963c1ba8c33932549d5fe98bd184932689a40aeba95043eca31dd6824f566197c546b60905555eccaf407408a5f0f200247bb0907450d309b0a70b245102

src/crypto/sha256.cpp

@@ -478,7 +478,7 @@ TransformD64Type TransformD64 = sha256::TransformD64;
 TransformD64Type TransformD64_4way = nullptr;
 TransformD64Type TransformD64_8way = nullptr;
 
-#if defined(USE_ASM) && (defined(__x86_64__) || defined(__amd64__))
+#if defined(USE_ASM) && (defined(__x86_64__) || defined(__amd64__) || defined(__i386__))
 // We can't use cpuid.h's __get_cpuid as it does not support subleafs.
 void inline cpuid(uint32_t leaf, uint32_t subleaf, uint32_t& a, uint32_t& b, uint32_t& c, uint32_t& d)
 {
@@ -491,12 +491,14 @@ void inline cpuid(uint32_t leaf, uint32_t subleaf, uint32_t& a, uint32_t& b, uin
 std::string SHA256AutoDetect()
 {
     std::string ret = "standard";
-#if defined(USE_ASM) && (defined(__x86_64__) || defined(__amd64__))
+#if defined(USE_ASM) && (defined(__x86_64__) || defined(__amd64__) || defined(__i386__))
     uint32_t eax, ebx, ecx, edx;
     cpuid(1, 0, eax, ebx, ecx, edx);
     if ((ecx >> 19) & 1) {
+#if defined(__x86_64__) || defined(__amd64__)
         Transform = sha256_sse4::Transform;
         TransformD64 = TransformD64Wrapper<sha256_sse4::Transform>;
+#endif
 #if defined(ENABLE_SSE41) && !defined(BUILD_BITCOIN_INTERNAL)
         TransformD64_4way = sha256d64_sse41::Transform_4way;
         ret = "sse4(1way+4way)";