[PATCH] D42579: [sanitizer] Implement MonotonicNanoTime for Windows

[Kostya Kortchinsky via Phabricator via llvm-commits]

cryptoad created this revision.
cryptoad added reviewers: rnk, alekseyshl.
Herald added subscribers: Sanitizers, delcypher, kubamracek.

Implement `MonotonicNanoTime` using `QueryPerformanceCounter`.

This function is used by Scudo & the 64-bit Primary allocator. Implementing it
now means that the release-to-OS mechanism of the Primary will kick in (it
never did since the function returned 0 always), but `ReleaseMemoryPagesToOS` is
still not currently implemented for Windows.

Performance wise, this adds a syscall & a 64-bit division per call to
`MonotonicNanoTime` so the impact might not be negligible, but I don't think
there is a way around it.


Repository:
  rCRT Compiler Runtime

https://reviews.llvm.org/D42579

Files:
  lib/sanitizer_common/sanitizer_win.cc


Index: lib/sanitizer_common/sanitizer_win.cc
===================================================================
--- lib/sanitizer_common/sanitizer_win.cc
+++ lib/sanitizer_common/sanitizer_win.cc
@@ -506,7 +506,18 @@
 }
 
 u64 MonotonicNanoTime() {
-  return 0;
+  static LARGE_INTEGER base, frequency = {0};
+  LARGE_INTEGER current, ns;
+  if (UNLIKELY(frequency.QuadPart == 0)) {
+    QueryPerformanceFrequency(&frequency);
+    QueryPerformanceCounter(&base);
+    CHECK_NE(frequency.QuadPart, 0);
+  }
+  QueryPerformanceCounter(&current);
+  ns.QuadPart = current.QuadPart - base.QuadPart;
+  ns.QuadPart *= 1000U * 1000000U;
+  ns.QuadPart /= frequency.QuadPart;
+  return ns.QuadPart;
 }
 
 void Abort() {


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