[llvm] [Analysis] Avoid running transform passes that have just been run (PR #112092)

[Arthur Eubanks via llvm-commits]

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@@ -5538,8 +5539,15 @@ void InstCombinePass::printPipeline(
   OS << '>';
 }
 
+char InstCombinePass::ID = 0;
+
 PreservedAnalyses InstCombinePass::run(Function &F,
                                        FunctionAnalysisManager &AM) {
+  auto &LRT = AM.getResult<LastRunTrackingAnalysis>(F);
+  // No changes since last InstCombine pass, exit early.
+  if (LRT.shouldSkip(&ID, Options))
+    return PreservedAnalyses::all();
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aeubanks wrote:

agreed about keeping this out of the pass manager, the pass manager shouldn't know which passes are supposed to be idempotent

https://github.com/llvm/llvm-project/pull/112092