[llvm] [SLP]Improve minbitwidth analysis. (PR #78976)

[Alexey Bataev via llvm-commits]

================
@@ -13245,23 +13271,32 @@ bool BoUpSLP::collectValuesToDemote(
   case Instruction::Mul:
   case Instruction::And:
   case Instruction::Or:
-  case Instruction::Xor:
-    if (!collectValuesToDemote(I->getOperand(0), ToDemote, DemotedConsts, Roots,
-                               Visited) ||
-        !collectValuesToDemote(I->getOperand(1), ToDemote, DemotedConsts, Roots,
-                               Visited))
+  case Instruction::Xor: {
+    unsigned Level1, Level2;
+    if (!collectValuesToDemote(I->getOperand(0), IsProfitableToDemoteRoot,
+                               BitWidth, ToDemote, DemotedConsts, Visited,
+                               Level1, IsProfitableToDemote) ||
+        !collectValuesToDemote(I->getOperand(1), IsProfitableToDemoteRoot,
+                               BitWidth, ToDemote, DemotedConsts, Visited,
+                               Level2, IsProfitableToDemote))
       return false;
+    MaxDepthLevel = std::max(Level1, Level2);
     break;
+  }
 
   // We can demote selects if we can demote their true and false values.
   case Instruction::Select: {
     Start = 1;
+    unsigned Level1, Level2;
     SelectInst *SI = cast<SelectInst>(I);
-    if (!collectValuesToDemote(SI->getTrueValue(), ToDemote, DemotedConsts,
-                               Roots, Visited) ||
-        !collectValuesToDemote(SI->getFalseValue(), ToDemote, DemotedConsts,
-                               Roots, Visited))
+    if (!collectValuesToDemote(SI->getTrueValue(), IsProfitableToDemoteRoot,
+                               BitWidth, ToDemote, DemotedConsts, Visited,
+                               Level1, IsProfitableToDemote) ||
+        !collectValuesToDemote(SI->getFalseValue(), IsProfitableToDemoteRoot,
+                               BitWidth, ToDemote, DemotedConsts, Visited,
+                               Level2, IsProfitableToDemote))
----------------
alexey-bataev wrote:

Yes, and that's fine. IsProfitableToDemote also used as the return value and if one of the functions sets it to false, it returns false and whole recursive call will return false. So, actually they both may set it to true, which is absolutely fine.

https://github.com/llvm/llvm-project/pull/78976