From a8d4927e29bb1acbf5f3267f368801847acd4222 Mon Sep 17 00:00:00 2001
From: Fernando Sahmkow <fsahmkow27@gmail.com>
Date: Sat, 16 Feb 2019 16:52:24 -0400
Subject: Corrections, documenting and fixes.

---
 src/common/uint128.cpp                 | 11 ++++++-----
 src/common/uint128.h                   |  9 +++++----
 src/core/arm/dynarmic/arm_dynarmic.cpp |  2 +-
 src/core/core_timing_util.cpp          |  5 ++---
 4 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/src/common/uint128.cpp b/src/common/uint128.cpp
index 8548ba808..2238a52c5 100644
--- a/src/common/uint128.cpp
+++ b/src/common/uint128.cpp
@@ -3,31 +3,32 @@
 
 #pragma intrinsic(_umul128)
 #endif
+#include <cstring>
 #include "common/uint128.h"
 
 namespace Common {
+
 u128 Multiply64Into128(u64 a, u64 b) {
-#ifdef _MSC_VER
     u128 result;
+#ifdef _MSC_VER
     result[0] = _umul128(a, b, &result[1]);
 #else
     unsigned __int128 tmp = a;
     tmp *= b;
-    u128 result;
     std::memcpy(&result, &tmp, sizeof(u128));
 #endif
     return result;
 }
 
-std::pair<u64, u64> Divide128On64(u128 dividend, u64 divisor) {
+std::pair<u64, u64> Divide128On32(u128 dividend, u32 divisor) {
     u64 remainder = dividend[0] % divisor;
     u64 accum = dividend[0] / divisor;
     if (dividend[1] == 0)
         return {accum, remainder};
     // We ignore dividend[1] / divisor as that overflows
-    u64 first_segment = (dividend[1] % divisor) << 32;
+    const u64 first_segment = (dividend[1] % divisor) << 32;
     accum += (first_segment / divisor) << 32;
-    u64 second_segment = (first_segment % divisor) << 32;
+    const u64 second_segment = (first_segment % divisor) << 32;
     accum += (second_segment / divisor);
     remainder += second_segment % divisor;
     if (remainder >= divisor) {
diff --git a/src/common/uint128.h b/src/common/uint128.h
index 45e384c33..52e6b46eb 100644
--- a/src/common/uint128.h
+++ b/src/common/uint128.h
@@ -1,13 +1,14 @@
-#include <array>
-#include <cstdint>
-#include <cstring>
+
 #include <utility>
 #include "common/common_types.h"
 
 namespace Common {
 
+// This function multiplies 2 u64 values and produces a u128 value;
 u128 Multiply64Into128(u64 a, u64 b);
 
-std::pair<u64, u64> Divide128On64(u128 dividend, u64 divisor);
+// This function divides a u128 by a u32 value and produces two u64 values:
+// the result of division and the remainder
+std::pair<u64, u64> Divide128On32(u128 dividend, u32 divisor);
 
 } // namespace Common
diff --git a/src/core/arm/dynarmic/arm_dynarmic.cpp b/src/core/arm/dynarmic/arm_dynarmic.cpp
index 25f76259b..4fdc12f11 100644
--- a/src/core/arm/dynarmic/arm_dynarmic.cpp
+++ b/src/core/arm/dynarmic/arm_dynarmic.cpp
@@ -152,7 +152,7 @@ std::unique_ptr<Dynarmic::A64::Jit> ARM_Dynarmic::MakeJit() const {
     config.tpidr_el0 = &cb->tpidr_el0;
     config.dczid_el0 = 4;
     config.ctr_el0 = 0x8444c004;
-    config.cntfrq_el0 = Timing::CNTFREQ; // Value from fusee.
+    config.cntfrq_el0 = Timing::CNTFREQ;
 
     // Unpredictable instructions
     config.define_unpredictable_behaviour = true;
diff --git a/src/core/core_timing_util.cpp b/src/core/core_timing_util.cpp
index aab4aa697..7942f30d6 100644
--- a/src/core/core_timing_util.cpp
+++ b/src/core/core_timing_util.cpp
@@ -62,9 +62,8 @@ s64 nsToCycles(u64 ns) {
 }
 
 u64 CpuCyclesToClockCycles(u64 ticks) {
-    u128 temporal = Common::Multiply64Into128(ticks, CNTFREQ);
-    std::pair<u64, u64> result = Common::Divide128On64(temporal, BASE_CLOCK_RATE);
-    return result.first;
+    const u128 temporal = Common::Multiply64Into128(ticks, CNTFREQ);
+    return Common::Divide128On32(temporal, static_cast<u32>(BASE_CLOCK_RATE)).first;
 }
 
 } // namespace Core::Timing
-- 
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