[PATCH] D105925: [TableGen] Warn when patterns are ignored due to impossible types

[Thomas Lively via Phabricator via llvm-commits]

tlively created this revision.
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There are some typing problems that cause TableGen to silently ignore CodeGen
patterns, which makes for a surprising and frustrating development workflow. To
clue developers in when their patterns are being ignored, emit a warning.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D105925

Files:
  llvm/utils/TableGen/CodeGenDAGPatterns.cpp


Index: llvm/utils/TableGen/CodeGenDAGPatterns.cpp
===================================================================
--- llvm/utils/TableGen/CodeGenDAGPatterns.cpp
+++ llvm/utils/TableGen/CodeGenDAGPatterns.cpp
@@ -4266,13 +4266,19 @@
   // that register class does not accept that type, the type inference
   // will lead to a contradiction, which is not an error however, but
   // a sign that this pattern will simply never match.
-  if (Temp.getOnlyTree()->hasPossibleType())
-    for (const auto &T : Pattern.getTrees())
-      if (T->hasPossibleType())
+  if (Temp.getOnlyTree()->hasPossibleType()) {
+    for (const auto &T : Pattern.getTrees()) {
+      if (T->hasPossibleType()) {
         AddPatternToMatch(&Pattern,
                           PatternToMatch(TheDef, Preds, T, Temp.getOnlyTree(),
                                          InstImpResults, Complexity,
                                          TheDef->getID()));
+      } else {
+        PrintWarning(Pattern.getRecord()->getLoc(),
+                     Twine("Ignoring pattern with impossible type"));
+      }
+    }
+  }
 }
 
 void CodeGenDAGPatterns::ParsePatterns() {


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