[llvm] [LV] Fix emission of debug message in legality check (PR #101924)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Madhur Amilkanthwar (madhur13490)

<details>
<summary>Changes</summary>

Successful vectorization message is emitted even
after "Result" is false.  "Result" = false indicates failure of one of the legality check and thus
successful message should not be printed.

---
Full diff: https://github.com/llvm/llvm-project/pull/101924.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp (+11-7) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
index 465d0df30e3f7..35c841f470261 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp
@@ -1441,10 +1441,12 @@ bool LoopVectorizationLegality::canVectorize(bool UseVPlanNativePath) {
   // Check whether the loop-related control flow in the loop nest is expected by
   // vectorizer.
   if (!canVectorizeLoopNestCFG(TheLoop, UseVPlanNativePath)) {
-    if (DoExtraAnalysis)
+    if (DoExtraAnalysis) {
+      LLVM_DEBUG(dbgs() << "LV legality check failed: loop nest");
       Result = false;
-    else
+    } else {
       return false;
+    }
   }
 
   // We need to have a loop header.
@@ -1509,11 +1511,6 @@ bool LoopVectorizationLegality::canVectorize(bool UseVPlanNativePath) {
       return false;
   }
 
-  LLVM_DEBUG(dbgs() << "LV: We can vectorize this loop"
-                    << (LAI->getRuntimePointerChecking()->Need
-                            ? " (with a runtime bound check)"
-                            : "")
-                    << "!\n");
 
   unsigned SCEVThreshold = VectorizeSCEVCheckThreshold;
   if (Hints->getForce() == LoopVectorizeHints::FK_Enabled)
@@ -1528,6 +1525,13 @@ bool LoopVectorizationLegality::canVectorize(bool UseVPlanNativePath) {
     else
       return false;
   }
+  if (Result) {
+    LLVM_DEBUG(dbgs() << "LV: We can vectorize this loop"
+                      << (LAI->getRuntimePointerChecking()->Need
+                            ? " (with a runtime bound check)"
+                            : "")
+                      << "!\n");
+  }
 
   // Okay! We've done all the tests. If any have failed, return false. Otherwise
   // we can vectorize, and at this point we don't have any other mem analysis

``````````

</details>


https://github.com/llvm/llvm-project/pull/101924