FEXCore: Optimize VPCMPISTRX implicit length calculation

With ASIMD this can be decently faster. With my microbenchmark this
makes pcmpistri ~6% faster.

With FEX-Emu#4336 this can be made even faster since the incoming data can stay
in vector registers; Removing some overhead of umov.

FEXCore/Source/CMakeLists.txt

@@ -105,6 +105,7 @@ set (SRCS
   Interface/Core/ArchHelpers/Arm64Emitter.cpp
   Interface/Core/Dispatcher/Dispatcher.cpp
   Interface/Core/Interpreter/Fallbacks/InterpreterFallbacks.cpp
+  Interface/Core/Interpreter/Fallbacks/StringCompareFallbacks.cpp
   Interface/Core/JIT/JIT.cpp
   Interface/Core/JIT/ALUOps.cpp
   Interface/Core/JIT/AtomicOps.cpp

FEXCore/Source/Interface/Core/Interpreter/Fallbacks/InterpreterFallbacks.cpp

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 #include <FEXCore/Core/CoreState.h>
 
 #include "Interface/Core/Interpreter/InterpreterOps.h"

FEXCore/Source/Interface/Core/Interpreter/Fallbacks/StringCompareFallbacks.cpp

@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: MIT
+#include "Interface/Core/Interpreter/Fallbacks/FallbackOpHandler.h"
+#include "Interface/Core/Interpreter/Fallbacks/VectorFallbacks.h"
+#include "Interface/IR/IR.h"
+
+#include <arm_neon.h>
+#include <cstring>
+
+namespace FEXCore::CPU {
+#ifdef _M_ARM_64
+FEXCORE_PRESERVE_ALL_ATTR static int32_t GetImplicitLength(const __uint128_t& data, uint16_t control) {
+  const auto is_using_words = (control & 1) != 0;
+
+  if (is_using_words) {
+    uint16x8_t a {};
+    memcpy(&a, &data, sizeof(a));
+    uint16x8_t VIndexes {};
+    const uint16x8_t VIndex16 = vdupq_n_u16(8);
+    uint16_t Indexes[8] = {
+      0, 1, 2, 3, 4, 5, 6, 7,
+    };
+    memcpy(&VIndexes, Indexes, sizeof(VIndexes));
+    auto MaskResult = vceqzq_u16(a);
+    auto SelectResult = vbslq_u16(MaskResult, VIndexes, VIndex16);
+    return vminvq_u16(SelectResult);
+  } else {
+    uint8x16_t a {};
+    memcpy(&a, &data, sizeof(a));
+    uint8x16_t VIndexes {};
+    const uint8x16_t VIndex16 = vdupq_n_u8(16);
+    uint8_t Indexes[16] = {
+      0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
+    };
+    memcpy(&VIndexes, Indexes, sizeof(VIndexes));
+    auto MaskResult = vceqzq_u8(a);
+    auto SelectResult = vbslq_u8(MaskResult, VIndexes, VIndex16);
+    return vminvq_u8(SelectResult);
+  }
+}
+#else
+FEXCORE_PRESERVE_ALL_ATTR static int32_t GetImplicitLength(const __uint128_t& data, uint16_t control) {
+  const auto* data_u8 = reinterpret_cast<const uint8_t*>(&data);
+  const auto is_using_words = (control & 1) != 0;
+
+  int32_t length = 0;
+
+  if (is_using_words) {
+    const auto get_word = [data_u8](int32_t index) {
+      const auto* src = data_u8 + (index * sizeof(uint16_t));
+
+      uint16_t element {};
+      std::memcpy(&element, src, sizeof(uint16_t));
+      return element;
+    };
+
+    while (length < 8 && get_word(length) != 0) {
+      length++;
+    }
+  } else {
+    while (length < 16 && data_u8[length] != 0) {
+      length++;
+    }
+  }
+
+  return length;
+}
+#endif
+
+// Essentially the same in terms of behavior with VPCMPESTRX instructions,
+// with the only difference being that the length of the string is encoded
+// as part of the data vectors passed in.
+//
+// i.e. Length is determined by the presence of a NUL (all-zero) character
+//      within the data.
+//
+//      If no NUL character exists, then the length of the strings are assumed
+//      to be the max length possible for the given character size specified
+//      in the control flags (16 characters for 8-bit, and 8 characters for 16-bit).
+//
+FEXCORE_PRESERVE_ALL_ATTR uint32_t OpHandlers<IR::OP_VPCMPISTRX>::handle(__uint128_t lhs, __uint128_t rhs, uint16_t control) {
+  // Subtract by 1 in order to make validity limits 0-based
+  const auto valid_lhs = GetImplicitLength(lhs, control) - 1;
+  const auto valid_rhs = GetImplicitLength(rhs, control) - 1;
+
+  return OpHandlers<IR::OP_VPCMPESTRX>::MainBody(lhs, valid_lhs, rhs, valid_rhs, control);
+}
+
+} // namespace FEXCore::CPU

FEXCore/Source/Interface/Core/Interpreter/Fallbacks/VectorFallbacks.h

@@ -6,9 +6,8 @@
 #include <cstdlib>
 #include <cstring>
 
-#include <FEXCore/IR/IR.h>
-
 #include "Interface/Core/Interpreter/Fallbacks/FallbackOpHandler.h"
+#include "Interface/IR/IR.h"
 
 namespace FEXCore::CPU {
 
@@ -344,51 +343,7 @@ struct OpHandlers<IR::OP_VPCMPESTRX> {
 
 template<>
 struct OpHandlers<IR::OP_VPCMPISTRX> {
-  // Essentially the same in terms of behavior with VPCMPESTRX instructions,
-  // with the only difference being that the length of the string is encoded
-  // as part of the data vectors passed in.
-  //
-  // i.e. Length is determined by the presence of a NUL (all-zero) character
-  //      within the data.
-  //
-  //      If no NUL character exists, then the length of the strings are assumed
-  //      to be the max length possible for the given character size specified
-  //      in the control flags (16 characters for 8-bit, and 8 characters for 16-bit).
-  //
-  FEXCORE_PRESERVE_ALL_ATTR static uint32_t handle(__uint128_t lhs, __uint128_t rhs, uint16_t control) {
-    // Subtract by 1 in order to make validity limits 0-based
-    const auto valid_lhs = GetImplicitLength(lhs, control) - 1;
-    const auto valid_rhs = GetImplicitLength(rhs, control) - 1;
-
-    return OpHandlers<IR::OP_VPCMPESTRX>::MainBody(lhs, valid_lhs, rhs, valid_rhs, control);
-  }
-
-  FEXCORE_PRESERVE_ALL_ATTR static int32_t GetImplicitLength(const __uint128_t& data, uint16_t control) {
-    const auto* data_u8 = reinterpret_cast<const uint8_t*>(&data);
-    const auto is_using_words = (control & 1) != 0;
-
-    int32_t length = 0;
-
-    if (is_using_words) {
-      const auto get_word = [data_u8](int32_t index) {
-        const auto* src = data_u8 + (index * sizeof(uint16_t));
-
-        uint16_t element {};
-        std::memcpy(&element, src, sizeof(uint16_t));
-        return element;
-      };
-
-      while (length < 8 && get_word(length) != 0) {
-        length++;
-      }
-    } else {
-      while (length < 16 && data_u8[length] != 0) {
-        length++;
-      }
-    }
-
-    return length;
-  }
+  FEXCORE_PRESERVE_ALL_ATTR static uint32_t handle(__uint128_t lhs, __uint128_t rhs, uint16_t control);
 };
 
 } // namespace FEXCore::CPU