Importing rustc-1.52.1

Change-Id: I3598a97301b4b2e71385e5a519f6d2ad946548b6

src/llvm-project/compiler-rt/test/fuzzer/EntropicScalePerExecTimeTest.cpp

diff --git a/src/llvm-project/compiler-rt/test/fuzzer/EntropicScalePerExecTimeTest.cpp b/src/llvm-project/compiler-rt/test/fuzzer/EntropicScalePerExecTimeTest.cpp
new file mode 100644
index 0000000..ec3a690
--- /dev/null
+++ b/src/llvm-project/compiler-rt/test/fuzzer/EntropicScalePerExecTimeTest.cpp
@@ -0,0 +1,33 @@
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// Tests whether scaling the Entropic scheduling weight based on input execution
+// time is effective or not. Inputs of size 10 will take at least 100
+// microseconds more than any input of size 1-9. The input of size 2 in the
+// corpus should be favored by the exec-time-scaled Entropic scheduling policy
+// than the input of size 10 in the corpus, eventually finding the crashing
+// input {0xab, 0xcd} with less executions.
+#include <chrono>
+#include <cstdint>
+#include <thread>
+
+static volatile int Sink;
+static volatile int *Nil = nullptr;
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+  if (Size > 10)
+    return 0; // To make the test quicker.
+
+  if (Size == 10) {
+    size_t ExecTimeUSec = 100;
+    std::this_thread::sleep_for(std::chrono::microseconds(ExecTimeUSec));
+
+    Sink = 0; // execute a lot slower than the crashing input below.
+  }
+
+  if (Size == 2 && Data[0] == 0xab && Data[1] == 0xcd)
+    *Nil = 42; // crash.
+
+  return 0;
+}