[llvm-branch-commits] [clang] [clang][analysis] Fix flaky clang/test/Analysis/live-stmts.cpp test (2nd attempt) (#127406) (PR #139591)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Balazs Benics (steakhal)

<details>
<summary>Changes</summary>

In my previous attempt (#<!-- -->126913) of fixing the flaky case was on a good track when I used the begin locations as a stable ordering. However, I forgot to consider the case when the begin locations are the same among the Exprs.

In an `EXPENSIVE_CHECKS` build, arrays are randomly shuffled prior to sorting them. This exposed the flaky behavior much more often basically breaking the "stability" of the vector - as it should. Because of this, I had to revert the previous fix attempt in #<!-- -->127034.

To fix this, I use this time `Expr::getID` for a stable ID for an Expr.

Hopefully fixes #<!-- -->126619
Hopefully fixes #<!-- -->126804

(cherry picked from commit f378e52ed3c6f8da4973f97f1ef043c2eb0da721)

---
Full diff: https://github.com/llvm/llvm-project/pull/139591.diff


2 Files Affected:

- (modified) clang/lib/Analysis/LiveVariables.cpp (+9-2) 
- (modified) clang/test/Analysis/live-stmts.cpp (+2) 


``````````diff
diff --git a/clang/lib/Analysis/LiveVariables.cpp b/clang/lib/Analysis/LiveVariables.cpp
index 481932ee59c8e..5fb5ee767a683 100644
--- a/clang/lib/Analysis/LiveVariables.cpp
+++ b/clang/lib/Analysis/LiveVariables.cpp
@@ -662,12 +662,19 @@ void LiveVariables::dumpExprLiveness(const SourceManager &M) {
 }
 
 void LiveVariablesImpl::dumpExprLiveness(const SourceManager &M) {
+  const ASTContext &Ctx = analysisContext.getASTContext();
+  auto ByIDs = [&Ctx](const Expr *L, const Expr *R) {
+    return L->getID(Ctx) < R->getID(Ctx);
+  };
+
   // Don't iterate over blockEndsToLiveness directly because it's not sorted.
   for (const CFGBlock *B : *analysisContext.getCFG()) {
-
     llvm::errs() << "\n[ B" << B->getBlockID()
                  << " (live expressions at block exit) ]\n";
-    for (const Expr *E : blocksEndToLiveness[B].liveExprs) {
+    std::vector<const Expr *> LiveExprs;
+    llvm::append_range(LiveExprs, blocksEndToLiveness[B].liveExprs);
+    llvm::sort(LiveExprs, ByIDs);
+    for (const Expr *E : LiveExprs) {
       llvm::errs() << "\n";
       E->dump();
     }
diff --git a/clang/test/Analysis/live-stmts.cpp b/clang/test/Analysis/live-stmts.cpp
index c60f522588e39..ca2ff6da8b133 100644
--- a/clang/test/Analysis/live-stmts.cpp
+++ b/clang/test/Analysis/live-stmts.cpp
@@ -44,6 +44,8 @@ int testThatDumperWorks(int x, int y, int z) {
 // CHECK-NEXT: ImplicitCastExpr {{.*}} <IntegralToBoolean>
 // CHECK-NEXT: `-ImplicitCastExpr {{.*}} <LValueToRValue>
 // CHECK-NEXT:   `-DeclRefExpr {{.*}} 'x' 'int'
+// CHECK-EMPTY:
+// CHECK-EMPTY:
 // CHECK: [ B4 (live expressions at block exit) ]
 // CHECK-EMPTY:
 // CHECK-NEXT: DeclRefExpr {{.*}} 'y' 'int'

``````````

</details>


https://github.com/llvm/llvm-project/pull/139591