[TSan, NFC] Eliminate useless calculations in TSan (#145283)

Previously, TSan repeatedly calculated some values in some cases, and
this change eliminates these duplicate calculations.

Author: Camsyn

compiler-rt/lib/tsan/rtl/tsan_rtl.cpp

@@ -624,6 +624,7 @@ void MapShadow(uptr addr, uptr size) {
   static uptr mapped_meta_end = 0;
   uptr meta_begin = (uptr)MemToMeta(addr);
   uptr meta_end = (uptr)MemToMeta(addr + size);
+  // Windows wants 64K alignment.
   meta_begin = RoundDownTo(meta_begin, 64 << 10);
   meta_end = RoundUpTo(meta_end, 64 << 10);
   if (!data_mapped) {
@@ -634,9 +635,6 @@ void MapShadow(uptr addr, uptr size) {
       Die();
   } else {
     // Mapping continuous heap.
-    // Windows wants 64K alignment.
-    meta_begin = RoundDownTo(meta_begin, 64 << 10);
-    meta_end = RoundUpTo(meta_end, 64 << 10);
     CHECK_GT(meta_end, mapped_meta_end);
     if (meta_begin < mapped_meta_end)
       meta_begin = mapped_meta_end;

compiler-rt/lib/tsan/rtl/tsan_sync.cpp

@@ -247,11 +247,14 @@ void MetaMap::MoveMemory(uptr src, uptr dst, uptr sz) {
   CHECK_NE(src, dst);
   CHECK_NE(sz, 0);
   uptr diff = dst - src;
-  u32 *src_meta = MemToMeta(src);
-  u32 *dst_meta = MemToMeta(dst);
-  u32 *src_meta_end = MemToMeta(src + sz);
-  uptr inc = 1;
-  if (dst > src) {
+  u32 *src_meta, *dst_meta, *src_meta_end;
+  uptr inc;
+  if (dst < src) {
+    src_meta = MemToMeta(src);
+    dst_meta = MemToMeta(dst);
+    src_meta_end = MemToMeta(src + sz);
+    inc = 1;
+  } else {
     src_meta = MemToMeta(src + sz) - 1;
     dst_meta = MemToMeta(dst + sz) - 1;
     src_meta_end = MemToMeta(src) - 1;