From 4eec1710c51865b47480bc63a736a3719496679d Mon Sep 17 00:00:00 2001
From: John Regehr <regehr@cs.utah.edu>
Date: Mon, 10 Jan 2022 22:24:23 -0700
Subject: allow llvm-reduce, if asked, to run its set of passes more than once,
 taking longer to finish but also potentially resulting in a smaller reduced
 file.

---
 llvm/tools/llvm-reduce/DeltaManager.cpp | 35 ++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

(limited to 'llvm/tools/llvm-reduce/DeltaManager.cpp')

diff --git a/llvm/tools/llvm-reduce/DeltaManager.cpp b/llvm/tools/llvm-reduce/DeltaManager.cpp
index 59edf73..4d646a7 100644
--- a/llvm/tools/llvm-reduce/DeltaManager.cpp
+++ b/llvm/tools/llvm-reduce/DeltaManager.cpp
@@ -103,15 +103,32 @@ void llvm::printDeltaPasses(raw_ostream &OS) {
 #undef DELTA_PASS
 }
 
-void llvm::runDeltaPasses(TestRunner &Tester) {
-  if (DeltaPasses.empty()) {
-    runAllDeltaPasses(Tester);
-  } else {
-    StringRef Passes = DeltaPasses;
-    while (!Passes.empty()) {
-      auto Split = Passes.split(",");
-      runDeltaPassName(Tester, Split.first);
-      Passes = Split.second;
+// FIXME: We might want to use a different metric than "number of
+// bytes in serialized IR" to detect non-progress of the main delta
+// loop
+static int getIRSize(TestRunner &Tester) {
+  std::string Str;
+  raw_string_ostream SS(Str);
+  Tester.getProgram().print(SS, /*AnnotationWriter=*/nullptr);
+  return Str.length();
+}
+
+void llvm::runDeltaPasses(TestRunner &Tester, int MaxPassIterations) {
+  int OldSize = getIRSize(Tester);
+  for (int Iter = 0; Iter < MaxPassIterations; ++Iter) {
+    if (DeltaPasses.empty()) {
+      runAllDeltaPasses(Tester);
+    } else {
+      StringRef Passes = DeltaPasses;
+      while (!Passes.empty()) {
+        auto Split = Passes.split(",");
+        runDeltaPassName(Tester, Split.first);
+        Passes = Split.second;
+      }
     }
+    int NewSize = getIRSize(Tester);
+    if (NewSize >= OldSize)
+      break;
+    OldSize = NewSize;
   }
 }
-- 
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