[llvm] [LoopUnroll] UnrollRuntimeMultiExit takes precedence over TTI. (PR #134259)

[David Green via llvm-commits]

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@@ -633,14 +629,21 @@ bool llvm::UnrollRuntimeLoopRemainder(
     if (!PreserveLCSSA)
       return false;
 
-    if (!RuntimeUnrollMultiExit &&
-        !canProfitablyRuntimeUnrollMultiExitLoop(L, OtherExits, LatchExit,
-                                                 UseEpilogRemainder)) {
-      LLVM_DEBUG(
-          dbgs()
-          << "Multiple exit/exiting blocks in loop and multi-exit unrolling not "
-             "enabled!\n");
-      return false;
+    // Priority goes to UnrollRuntimeMultiExit if it's supplied.
+    if (UnrollRuntimeMultiExit.getNumOccurrences()) {
+      if (!UnrollRuntimeMultiExit)
+        return false;
+    } else {
+      // Otherwise perform multi-exit unrolling, if either the target indicates
+      // it is profitable or the general profitability heuristics apply.
+      if (!RuntimeUnrollMultiExit &&
+          !canProfitablyRuntimeUnrollMultiExitLoop(L, OtherExits, LatchExit,
+                                                   UseEpilogRemainder)) {
+        LLVM_DEBUG(dbgs() << "Multiple exit/exiting blocks in loop and "
+                             "multi-exit unrolling not "
+                             "enabled!\n");
----------------
davemgreen wrote:

enabled! can be combined with the previous line.

https://github.com/llvm/llvm-project/pull/134259