[SCEV] Cache DataLayout in class (NFC)

PR #96919 caused a minor compile-time regression, mostly because
SCEV now goes through an extra out-of-line function to fetch the
data layout, and does this a lot. Cache the DataLayout in SCEV
to avoid these repeated calls.

Author: nikic

llvm/include/llvm/Analysis/ScalarEvolution.h

@@ -1265,9 +1265,7 @@ class ScalarEvolution {
 
   /// Return the DataLayout associated with the module this SCEV instance is
   /// operating on.
-  const DataLayout &getDataLayout() const {
-    return F.getDataLayout();
-  }
+  const DataLayout &getDataLayout() const { return DL; }
 
   const SCEVPredicate *getEqualPredicate(const SCEV *LHS, const SCEV *RHS);
   const SCEVPredicate *getComparePredicate(ICmpInst::Predicate Pred,
@@ -1373,6 +1371,9 @@ class ScalarEvolution {
   /// The function we are analyzing.
   Function &F;
 
+  /// Data layout of the module.
+  const DataLayout &DL;
+
   /// Does the module have any calls to the llvm.experimental.guard intrinsic
   /// at all?  If this is false, we avoid doing work that will only help if
   /// thare are guards present in the IR.

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -13509,7 +13509,7 @@ ScalarEvolution::SCEVCallbackVH::SCEVCallbackVH(Value *V, ScalarEvolution *se)
 ScalarEvolution::ScalarEvolution(Function &F, TargetLibraryInfo &TLI,
                                  AssumptionCache &AC, DominatorTree &DT,
                                  LoopInfo &LI)
-    : F(F), TLI(TLI), AC(AC), DT(DT), LI(LI),
+    : F(F), DL(F.getDataLayout()), TLI(TLI), AC(AC), DT(DT), LI(LI),
       CouldNotCompute(new SCEVCouldNotCompute()), ValuesAtScopes(64),
       LoopDispositions(64), BlockDispositions(64) {
   // To use guards for proving predicates, we need to scan every instruction in
@@ -13528,8 +13528,8 @@ ScalarEvolution::ScalarEvolution(Function &F, TargetLibraryInfo &TLI,
 }
 
 ScalarEvolution::ScalarEvolution(ScalarEvolution &&Arg)
-    : F(Arg.F), HasGuards(Arg.HasGuards), TLI(Arg.TLI), AC(Arg.AC), DT(Arg.DT),
-      LI(Arg.LI), CouldNotCompute(std::move(Arg.CouldNotCompute)),
+    : F(Arg.F), DL(Arg.DL), HasGuards(Arg.HasGuards), TLI(Arg.TLI), AC(Arg.AC),
+      DT(Arg.DT), LI(Arg.LI), CouldNotCompute(std::move(Arg.CouldNotCompute)),
       ValueExprMap(std::move(Arg.ValueExprMap)),
       PendingLoopPredicates(std::move(Arg.PendingLoopPredicates)),
       PendingPhiRanges(std::move(Arg.PendingPhiRanges)),