DataLayout is mandatory, update the API to reflect it with references.

Summary:
Now that the DataLayout is a mandatory part of the module, let's start
cleaning the codebase. This patch is a first attempt at doing that.

This patch is not exactly NFC as for instance some places were passing
a nullptr instead of the DataLayout, possibly just because there was a
default value on the DataLayout argument to many functions in the API.
Even though it is not purely NFC, there is no change in the
validation.

I turned as many pointer to DataLayout to references, this helped
figuring out all the places where a nullptr could come up.

I had initially a local version of this patch broken into over 30
independant, commits but some later commit were cleaning the API and
touching part of the code modified in the previous commits, so it
seemed cleaner without the intermediate state.

Test Plan:

Reviewers: echristo

Subscribers: llvm-commits

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231740 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/LoopRerollPass.cpp

@@ -160,7 +160,6 @@ namespace {
     AliasAnalysis *AA;
     LoopInfo *LI;
     ScalarEvolution *SE;
-    const DataLayout *DL;
     TargetLibraryInfo *TLI;
     DominatorTree *DT;
 
@@ -367,10 +366,8 @@ namespace {
     struct DAGRootTracker {
       DAGRootTracker(LoopReroll *Parent, Loop *L, Instruction *IV,
                      ScalarEvolution *SE, AliasAnalysis *AA,
-                     TargetLibraryInfo *TLI, const DataLayout *DL)
-        : Parent(Parent), L(L), SE(SE), AA(AA), TLI(TLI),
-          DL(DL), IV(IV) {
-      }
+                     TargetLibraryInfo *TLI)
+          : Parent(Parent), L(L), SE(SE), AA(AA), TLI(TLI), IV(IV) {}
 
       /// Stage 1: Find all the DAG roots for the induction variable.
       bool findRoots();
@@ -416,7 +413,6 @@ namespace {
       ScalarEvolution *SE;
       AliasAnalysis *AA;
       TargetLibraryInfo *TLI;
-      const DataLayout *DL;
 
       // The loop induction variable.
       Instruction *IV;
@@ -1131,7 +1127,7 @@ bool LoopReroll::DAGRootTracker::validate(ReductionTracker &Reductions) {
         // needed because otherwise isSafeToSpeculativelyExecute returns
         // false on PHI nodes.
         if (!isa<PHINode>(I) && !isSimpleLoadStore(I) &&
-            !isSafeToSpeculativelyExecute(I, DL))
+            !isSafeToSpeculativelyExecute(I))
           // Intervening instructions cause side effects.
           FutureSideEffects = true;
       }
@@ -1161,11 +1157,10 @@ bool LoopReroll::DAGRootTracker::validate(ReductionTracker &Reductions) {
       // side effects, and this instruction might also, then we can't reorder
       // them, and this matching fails. As an exception, we allow the alias
       // set tracker to handle regular (simple) load/store dependencies.
-      if (FutureSideEffects &&
-            ((!isSimpleLoadStore(BaseInst) &&
-              !isSafeToSpeculativelyExecute(BaseInst, DL)) ||
-             (!isSimpleLoadStore(RootInst) &&
-              !isSafeToSpeculativelyExecute(RootInst, DL)))) {
+      if (FutureSideEffects && ((!isSimpleLoadStore(BaseInst) &&
+                                 !isSafeToSpeculativelyExecute(BaseInst)) ||
+                                (!isSimpleLoadStore(RootInst) &&
+                                 !isSafeToSpeculativelyExecute(RootInst)))) {
         DEBUG(dbgs() << "LRR: iteration root match failed at " << *BaseInst <<
                         " vs. " << *RootInst <<
                         " (side effects prevent reordering)\n");
@@ -1272,6 +1267,7 @@ void LoopReroll::DAGRootTracker::replace(const SCEV *IterCount) {
 
     ++J;
   }
+  const DataLayout &DL = Header->getModule()->getDataLayout();
 
   // We need to create a new induction variable for each different BaseInst.
   for (auto &DRS : RootSets) {
@@ -1284,7 +1280,7 @@ void LoopReroll::DAGRootTracker::replace(const SCEV *IterCount) {
                          SE->getConstant(RealIVSCEV->getType(), 1),
                          L, SCEV::FlagAnyWrap));
     { // Limit the lifetime of SCEVExpander.
-      SCEVExpander Expander(*SE, "reroll");
+      SCEVExpander Expander(*SE, DL, "reroll");
       Value *NewIV = Expander.expandCodeFor(H, IV->getType(), Header->begin());
 
       for (auto &KV : Uses) {
@@ -1324,7 +1320,7 @@ void LoopReroll::DAGRootTracker::replace(const SCEV *IterCount) {
     }
   }
 
-  SimplifyInstructionsInBlock(Header, DL, TLI);
+  SimplifyInstructionsInBlock(Header, TLI);
   DeleteDeadPHIs(Header, TLI);
 }
 
@@ -1448,7 +1444,7 @@ void LoopReroll::ReductionTracker::replaceSelected() {
 bool LoopReroll::reroll(Instruction *IV, Loop *L, BasicBlock *Header,
                         const SCEV *IterCount,
                         ReductionTracker &Reductions) {
-  DAGRootTracker DAGRoots(this, L, IV, SE, AA, TLI, DL);
+  DAGRootTracker DAGRoots(this, L, IV, SE, AA, TLI);
 
   if (!DAGRoots.findRoots())
     return false;
@@ -1477,7 +1473,6 @@ bool LoopReroll::runOnLoop(Loop *L, LPPassManager &LPM) {
   LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
   SE = &getAnalysis<ScalarEvolution>();
   TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
-  DL = &L->getHeader()->getModule()->getDataLayout();
   DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
 
   BasicBlock *Header = L->getHeader();