8313882: Fix -Wconversion warnings in runtime code

src/hotspot/share/runtime/arguments.cpp

@@ -1579,8 +1579,8 @@ void Arguments::set_heap_size() {
   // then set it as fraction of the size of physical memory,
   // respecting the maximum and minimum sizes of the heap.
   if (FLAG_IS_DEFAULT(MaxHeapSize)) {
-    julong reasonable_max = (julong)((phys_mem * (julong)MaxRAMPercentage) / 100);
-    const julong reasonable_min = (julong)((phys_mem * (julong)MinRAMPercentage) / 100);
+    julong reasonable_max = (julong)(((double)phys_mem * MaxRAMPercentage) / 100);
+    const julong reasonable_min = (julong)(((double)phys_mem * MinRAMPercentage) / 100);
     if (reasonable_min < MaxHeapSize) {
       // Small physical memory, so use a minimum fraction of it for the heap
       reasonable_max = reasonable_min;
@@ -1664,7 +1664,7 @@ void Arguments::set_heap_size() {
     reasonable_minimum = limit_heap_by_allocatable_memory(reasonable_minimum);
 
     if (InitialHeapSize == 0) {
-      julong reasonable_initial = (julong)((phys_mem * (julong)InitialRAMPercentage) / 100);
+      julong reasonable_initial = (julong)(((double)phys_mem * InitialRAMPercentage) / 100);
       reasonable_initial = limit_heap_by_allocatable_memory(reasonable_initial);
 
       reasonable_initial = MAX3(reasonable_initial, reasonable_minimum, (julong)MinHeapSize);
@@ -2735,7 +2735,7 @@ jint Arguments::parse_each_vm_init_arg(const JavaVMInitArgs* args, bool* patch_m
         return JNI_EINVAL;
       }
 
-      if (FLAG_SET_CMDLINE(MaxTenuringThreshold, (uint)max_tenuring_thresh) != JVMFlag::SUCCESS) {
+      if (FLAG_SET_CMDLINE(MaxTenuringThreshold, max_tenuring_thresh) != JVMFlag::SUCCESS) {
         return JNI_EINVAL;
       }
 

src/hotspot/share/runtime/objectMonitor.hpp

@@ -235,7 +235,7 @@ class ObjectMonitor : public CHeapObj<mtObjectMonitor> {
   // to the ObjectMonitor reference manipulation code:
   //
   #define OM_OFFSET_NO_MONITOR_VALUE_TAG(f) \
-    ((in_bytes(ObjectMonitor::f ## _offset())) - (unsigned)markWord::monitor_value)
+    ((in_bytes(ObjectMonitor::f ## _offset())) - (int)markWord::monitor_value)
 
   markWord           header() const;
   volatile markWord* header_addr();

src/hotspot/share/runtime/os.cpp

@@ -136,11 +136,11 @@ char* os::iso8601_time(jlong milliseconds_since_19700101, char* buffer, size_t b
     assert(false, "buffer_length too small");
     return nullptr;
   }
-  const int milliseconds_per_microsecond = 1000;
+  const int milliseconds_per_second = 1000;
   const time_t seconds_since_19700101 =
-    milliseconds_since_19700101 / milliseconds_per_microsecond;
+    milliseconds_since_19700101 / milliseconds_per_second;
   const int milliseconds_after_second =
-    checked_cast<int>(milliseconds_since_19700101 % milliseconds_per_microsecond);
+    checked_cast<int>(milliseconds_since_19700101 % milliseconds_per_second);
   // Convert the time value to a tm and timezone variable
   struct tm time_struct;
   if (utc) {

src/hotspot/share/runtime/sharedRuntime.cpp

@@ -2343,22 +2343,22 @@ class MethodArityHistogram {
 
   void print_histogram_helper(int n, uint64_t* histo, const char* name) {
     const int N = MIN2(9, n);
-    double sum = 0;
-    double weighted_sum = 0;
-    for (int i = 0; i <= n; i++) { sum += (double)histo[i]; weighted_sum += (double)(i*histo[i]); }
-    if (sum >= 1.0) { // prevent divide by zero or divide overflow
-      double rest = sum;
+    uint64_t sum = 0;
+    uint64_t weighted_sum = 0;
+    for (int i = 0; i <= n; i++) { sum += histo[i]; weighted_sum += (i*histo[i]); }
+    if (sum >= 1) { // prevent divide by zero or divide overflow
+      uint64_t rest = sum;
       double percent = (double)sum / 100;
       for (int i = 0; i <= N; i++) {
-        rest -= (double)histo[i];
+        rest -= histo[i];
         tty->print_cr("%4d: " UINT64_FORMAT_W(12) " (%5.1f%%)", i, histo[i], (double)histo[i] / percent);
       }
-      tty->print_cr("rest: " INT64_FORMAT_W(12) " (%5.1f%%)", (int64_t)rest, rest / percent);
-      tty->print_cr("(avg. %s = %3.1f, max = %d)", name, weighted_sum / sum, n);
+      tty->print_cr("rest: " INT64_FORMAT_W(12) " (%5.1f%%)", rest, (double)rest / percent);
+      tty->print_cr("(avg. %s = %3.1f, max = %d)", name, (double)weighted_sum / (double)sum, n);
       tty->print_cr("(total # of compiled calls = " INT64_FORMAT_W(14) ")", _total_compiled_calls);
       tty->print_cr("(max # of compiled calls   = " INT64_FORMAT_W(14) ")", _max_compiled_calls_per_method);
     } else {
-      tty->print_cr("Histogram generation failed for %s. n = %d, sum = %7.5f", name, n, sum);
+      tty->print_cr("Histogram generation failed for %s. n = %d, sum = %zu", name, n, sum);
     }
   }
 

src/hotspot/share/runtime/threadHeapSampler.cpp

@@ -356,7 +356,7 @@ double ThreadHeapSampler::fast_log2(const double& d) {
   assert(sizeof(d) == sizeof(x),
          "double and uint64_t do not have the same size");
   x = *reinterpret_cast<const uint64_t*>(&d);
-  const uint32_t x_high = (uint32_t)(x >> 32);
+  const uint32_t x_high = checked_cast<uint32_t>(x >> 32);
   assert(FastLogNumBits <= 20, "FastLogNumBits should be less than 20.");
   const uint32_t y = x_high >> (20 - FastLogNumBits) & FastLogMask;
   const int32_t exponent = ((x_high >> 20) & 0x7FF) - 1023;