[SCCP] Fold y = f(x) = (Cx mod M) ∈ R into x ∈ R'

llvm/include/llvm/Transforms/Utils/SCCPSolver.h

@@ -194,10 +194,16 @@ class SCCPSolver {
   LLVM_ABI void visit(Instruction *I);
   LLVM_ABI void visitCall(CallInst &I);
 
+  /// Simplify instructions in \p BB using the solver's lattice information.
+  /// When \p Eager is true, also apply more aggressive folds that may rewrite
+  /// IR into forms less friendly to earlier canonicalization passes. Keep eager
+  /// mode for later optimization points where exposing extra range-based folds
+  /// outweighs the risk of hiding canonical patterns.
   LLVM_ABI bool simplifyInstsInBlock(BasicBlock &BB,
                                      SmallPtrSetImpl<Value *> &InsertedValues,
                                      Statistic &InstRemovedStat,
-                                     Statistic &InstReplacedStat);
+                                     Statistic &InstReplacedStat,
+                                     bool Eager = false);
 
   LLVM_ABI bool removeNonFeasibleEdges(BasicBlock *BB, DomTreeUpdater &DTU,
                                        BasicBlock *&NewUnreachableBB) const;

llvm/lib/Transforms/Scalar/SCCP.cpp

@@ -102,7 +102,8 @@ static bool runSCCP(Function &F, const DataLayout &DL,
     }
 
     MadeChanges |= Solver.simplifyInstsInBlock(BB, InsertedValues,
-                                               NumInstRemoved, NumInstReplaced);
+                                               NumInstRemoved, NumInstReplaced,
+                                               /*Eager=*/true);
   }
 
   // Remove unreachable blocks and non-feasible edges.