[llvm] [hwasan][NFCI] Rename ClRandomSkipRate to ClRandomKeepRate (PR #126990)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Thurston Dang (thurstond)

<details>
<summary>Changes</summary>

The meaning of ClRandomSkipRate was inverted in
https://github.com/llvm/llvm-project/pull/88070 but the variable name was not changed. This patch fixes it to avoid confusion.

Additionally, it elaborates the flag description to mention the interaction between the random keep rate and hotness cutoff.

---
Full diff: https://github.com/llvm/llvm-project/pull/126990.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp (+7-5) 


``````````diff
diff --git a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
index 645c102752692..5a184cc066aab 100644
--- a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -195,9 +195,11 @@ static cl::opt<int> ClHotPercentileCutoff("hwasan-percentile-cutoff-hot",
                                           cl::desc("Hot percentile cutoff."));
 
 static cl::opt<float>
-    ClRandomSkipRate("hwasan-random-rate",
+    ClRandomKeepRate("hwasan-random-rate",
                      cl::desc("Probability value in the range [0.0, 1.0] "
-                              "to keep instrumentation of a function."));
+                              "to keep instrumentation of a function. "
+                              "Note: instrumentation can be skipped randomly "
+                              "OR because of the hot percentile cutoff."));
 
 STATISTIC(NumTotalFuncs, "Number of total funcs");
 STATISTIC(NumInstrumentedFuncs, "Number of instrumented funcs");
@@ -301,7 +303,7 @@ class HWAddressSanitizer {
       : M(M), SSI(SSI) {
     this->Recover = optOr(ClRecover, Recover);
     this->CompileKernel = optOr(ClEnableKhwasan, CompileKernel);
-    this->Rng = ClRandomSkipRate.getNumOccurrences() ? M.createRNG(DEBUG_TYPE)
+    this->Rng = ClRandomKeepRate.getNumOccurrences() ? M.createRNG(DEBUG_TYPE)
                                                      : nullptr;
 
     initializeModule();
@@ -1599,9 +1601,9 @@ bool HWAddressSanitizer::selectiveInstrumentationShouldSkip(
   };
 
   auto SkipRandom = [&]() {
-    if (!ClRandomSkipRate.getNumOccurrences())
+    if (!ClRandomKeepRate.getNumOccurrences())
       return false;
-    std::bernoulli_distribution D(ClRandomSkipRate);
+    std::bernoulli_distribution D(ClRandomKeepRate);
     return !D(*Rng);
   };
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/126990