Add a flag to debug automatic variable initialization

Summary:
Add -ftrivial-auto-var-init-stop-after= to limit the number of times
stack variables are initialized when -ftrivial-auto-var-init= is used to
initialize stack variables to zero or a pattern. This flag can be used
to bisect uninitialized uses of a stack variable exposed by automatic
variable initialization, such as http://crrev.com/c/2020401.

Reviewers: jfb, vitalybuka, kcc, glider, rsmith, rjmccall, pcc, eugenis, vlad.tsyrklevich

Reviewed By: jfb

Subscribers: phosek, hubert.reinterpretcast, srhines, MaskRay, george.burgess.iv, dexonsmith, inglorion, gbiv, llozano, manojgupta, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D77168

1 files changed, 25 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 3d7a87308128..26d34fa293e4 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -6023,3 +6023,28 @@ CharUnits CodeGenModule::getNaturalTypeAlignment(QualType T,
   }
   return Alignment;
 }
+
+bool CodeGenModule::stopAutoInit() {
+  unsigned StopAfter = getContext().getLangOpts().TrivialAutoVarInitStopAfter;
+  if (StopAfter) {
+    // This number is positive only when -ftrivial-auto-var-init-stop-after=* is
+    // used
+    if (NumAutoVarInit >= StopAfter) {
+      return true;
+    }
+    if (!NumAutoVarInit) {
+      unsigned DiagID = getDiags().getCustomDiagID(
+          DiagnosticsEngine::Warning,
+          "-ftrivial-auto-var-init-stop-after=%0 has been enabled to limit the "
+          "number of times ftrivial-auto-var-init=%1 gets applied.");
+      getDiags().Report(DiagID)
+          << StopAfter
+          << (getContext().getLangOpts().getTrivialAutoVarInit() ==
+                      LangOptions::TrivialAutoVarInitKind::Zero
+                  ? "zero"
+                  : "pattern");
+    }
+    ++NumAutoVarInit;
+  }
+  return false;
+}