[LV] Emit remarks for vectorization decision before execute (NFCI).

Move the emission of remarks for the vectorization decision before
executing the plan, in preparation for
#154510.

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -10206,6 +10206,24 @@ bool LoopVectorizePass::processLoop(Loop *L) {
 
   bool DisableRuntimeUnroll = false;
   MDNode *OrigLoopID = L->getLoopID();
+
+  // Report the vectorization decision.
+  if (VF.Width.isScalar()) {
+    using namespace ore;
+    assert(IC > 1);
+    ORE->emit([&]() {
+      return OptimizationRemark(LV_NAME, "Interleaved", L->getStartLoc(),
+                                L->getHeader())
+             << "interleaved loop (interleaved count: "
+             << NV("InterleaveCount", IC) << ")";
+    });
+  } else {
+    // Report the vectorization decision.
+    reportVectorization(ORE, L, VF, IC);
+  }
+  if (ORE->allowExtraAnalysis(LV_NAME))
+    checkMixedPrecision(L, ORE);
+
   // If we decided that it is *legal* to interleave or vectorize the loop, then
   // do it.
 
@@ -10276,22 +10294,6 @@ bool LoopVectorizePass::processLoop(Loop *L) {
     if (!Checks.hasChecks() && !VF.Width.isScalar())
       DisableRuntimeUnroll = true;
   }
-  if (VF.Width.isScalar()) {
-    using namespace ore;
-    assert(IC > 1);
-    ORE->emit([&]() {
-      return OptimizationRemark(LV_NAME, "Interleaved", L->getStartLoc(),
-                                L->getHeader())
-             << "interleaved loop (interleaved count: "
-             << NV("InterleaveCount", IC) << ")";
-    });
-  } else {
-    // Report the vectorization decision.
-    reportVectorization(ORE, L, VF, IC);
-  }
-
-  if (ORE->allowExtraAnalysis(LV_NAME))
-    checkMixedPrecision(L, ORE);
 
   assert(DT->verify(DominatorTree::VerificationLevel::Fast) &&
          "DT not preserved correctly");