From c4693cc86f5e8b4de5c30263954dc55b866fc9cb Mon Sep 17 00:00:00 2001
From: Joao Paulo Magalhaes <dev@jpmag.me>
Date: Mon, 16 Nov 2020 11:58:03 +0000
Subject: [PATCH] re #33: win32 is working

---
 include/fast_float/float_common.h | 18 +++++++++++++++---
 tests/basictest.cpp               | 24 +++++++++++++++++++++---
 2 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/include/fast_float/float_common.h b/include/fast_float/float_common.h
index a98a54b..93782e9 100644
--- a/include/fast_float/float_common.h
+++ b/include/fast_float/float_common.h
@@ -90,6 +90,7 @@ struct value128 {
 /* result might be undefined when input_num is zero */
 fastfloat_really_inline int leading_zeroes(uint64_t input_num) {
 #ifdef FASTFLOAT_VISUAL_STUDIO
+#if defined(_M_X64) || defined(_M_ARM64)
   unsigned long leading_zero = 0;
   // Search the mask data from most significant bit (MSB)
   // to least significant bit (LSB) for a set bit (1).
@@ -97,6 +98,17 @@ fastfloat_really_inline int leading_zeroes(uint64_t input_num) {
     return (int)(63 - leading_zero);
   else
     return 64;
+#else
+    if(!input_num) return 64;
+    int n = 0;
+    if(input_num & uint64_t(0xffffffff00000000)) input_num >>= 32, n |= 32;
+    if(input_num & uint64_t(        0xffff0000)) input_num >>= 16, n |= 16;
+    if(input_num & uint64_t(            0xff00)) input_num >>=  8, n |=  8;
+    if(input_num & uint64_t(              0xf0)) input_num >>=  4, n |=  4;
+    if(input_num & uint64_t(               0xc)) input_num >>=  2, n |=  2;
+    if(input_num & uint64_t(               0x2)) input_num >>=  1, n |=  1;
+    return 63 - n;
+#endif
 #else
   return __builtin_clzll(input_num);
 #endif
@@ -109,9 +121,9 @@ fastfloat_really_inline int leading_zeroes(uint64_t input_num) {
 #if !defined(_M_X64) && !defined(_M_ARM64) // _umul128 for x86, arm
 // this is a slow emulation routine for 32-bit Windows
 //
-fastfloat_really_inline uint64_t __emulu(uint32_t x, uint32_t y) {
-  return x * (uint64_t)y;
-}
+//fastfloat_really_inline uint64_t __emulu(uint32_t x, uint32_t y) {
+//  return x * (uint64_t)y;
+//}
 fastfloat_really_inline uint64_t _umul128(uint64_t ab, uint64_t cd,
                                           uint64_t *hi) {
   uint64_t ad = __emulu((uint32_t)(ab >> 32), (uint32_t)cd);
diff --git a/tests/basictest.cpp b/tests/basictest.cpp
index 8acb9ca..8d9d750 100644
--- a/tests/basictest.cpp
+++ b/tests/basictest.cpp
@@ -1,9 +1,14 @@
 #include "fast_float/fast_float.h"
 #include <iomanip>
 
-inline void Assert(bool Assertion) {
-  if (!Assertion)
-    throw std::runtime_error("bug");
+#define Q(x) #x
+#define QUOTE(x) Q(x)
+#define Assert(assertion) \
+  if (!(assertion)) {\
+    AssertionFailed(__FILE__ ":" QUOTE(__LINE__) ": assertion failed: " #assertion);\
+  }
+inline void AssertionFailed(const char *msg) {
+    throw std::runtime_error(msg);
 }
 
 template <typename T> std::string to_string(T d) {
@@ -327,7 +332,20 @@ bool test_fixed_only() {
     return true;
   }
 
+  void test_leading_zeroes()
+  {
+      constexpr const uint64_t bit = 1;
+      Assert(fast_float::leading_zeroes(0) == 64);
+      Assert(fast_float::leading_zeroes(bit <<  0) == 63);
+      Assert(fast_float::leading_zeroes(bit <<  1) == 62);
+      Assert(fast_float::leading_zeroes(bit <<  2) == 61);
+      Assert(fast_float::leading_zeroes(bit << 61) ==  2);
+      Assert(fast_float::leading_zeroes(bit << 62) ==  1);
+      Assert(fast_float::leading_zeroes(bit << 63) ==  0);
+  }
+
 int main() {
+  test_leading_zeroes();
   Assert(test_fixed_only());
   Assert(test_scientific_only());
   Assert(issue8());