[CodeGen] Don't require AA in SDAGISel at -O0.

Before r247167, the pass manager builder controlled which AA
implementations were used, exporting them all in the AliasAnalysis
analysis group.

Now, AAResultsWrapperPass always uses BasicAA, but still uses other AA
implementations if made available in the pass pipeline.

But regardless, SDAGISel is required at O0, and really doesn't need to
be doing fancy optimizations based on useful AA results.

Don't require AA at CodeGenOpt::None, and only use it otherwise.

This does have a functional impact (and one testcase is pessimized
because we can't reuse a load).  But I think that's desirable no matter
what.

Note that this alone doesn't result in less DT computations: TwoAddress
was previously able to reuse the DT we computed for SDAG.  That will be
fixed separately.

Differential Revision: https://reviews.llvm.org/D32766

llvm-svn: 302611

1 files changed, 18 insertions, 8 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index c7eb9b80701..5e0feccb6b4 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -300,7 +300,7 @@ SelectionDAGISel::SelectionDAGISel(TargetMachine &tm,
   FuncInfo(new FunctionLoweringInfo()),
   CurDAG(new SelectionDAG(tm, OL)),
   SDB(new SelectionDAGBuilder(*CurDAG, *FuncInfo, OL)),
-  GFI(),
+  AA(), GFI(),
   OptLevel(OL),
   DAGSize(0) {
     initializeGCModuleInfoPass(*PassRegistry::getPassRegistry());
@@ -318,7 +318,8 @@ SelectionDAGISel::~SelectionDAGISel() {
 }
 
 void SelectionDAGISel::getAnalysisUsage(AnalysisUsage &AU) const {
-  AU.addRequired<AAResultsWrapperPass>();
+  if (OptLevel != CodeGenOpt::None)
+    AU.addRequired<AAResultsWrapperPass>();
   AU.addRequired<GCModuleInfo>();
   AU.addRequired<StackProtector>();
   AU.addPreserved<StackProtector>();
@@ -395,7 +396,6 @@ bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
   TII = MF->getSubtarget().getInstrInfo();
   TLI = MF->getSubtarget().getTargetLowering();
   RegInfo = &MF->getRegInfo();
-  AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
   LibInfo = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
   GFI = Fn.hasGC() ? &getAnalysis<GCModuleInfo>().getFunctionInfo(Fn) : nullptr;
   ORE = make_unique<OptimizationRemarkEmitter>(&Fn);
@@ -407,12 +407,22 @@ bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
   CurDAG->init(*MF, *ORE);
   FuncInfo->set(Fn, *MF, CurDAG);
 
+  // Now get the optional analyzes if we want to.
+  // This is based on the possibly changed OptLevel (after optnone is taken
+  // into account).  That's unfortunate but OK because it just means we won't
+  // ask for passes that have been required anyway.
+
   if (UseMBPI && OptLevel != CodeGenOpt::None)
     FuncInfo->BPI = &getAnalysis<BranchProbabilityInfoWrapperPass>().getBPI();
   else
     FuncInfo->BPI = nullptr;
 
-  SDB->init(GFI, *AA, LibInfo);
+  if (OptLevel != CodeGenOpt::None)
+    AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
+  else
+    AA = nullptr;
+
+  SDB->init(GFI, AA, LibInfo);
 
   MF->setHasInlineAsm(false);
 
@@ -716,7 +726,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
   {
     NamedRegionTimer T("combine1", "DAG Combining 1", GroupName,
                        GroupDescription, TimePassesIsEnabled);
-    CurDAG->Combine(BeforeLegalizeTypes, *AA, OptLevel);
+    CurDAG->Combine(BeforeLegalizeTypes, AA, OptLevel);
   }
 
   DEBUG(dbgs() << "Optimized lowered selection DAG: BB#" << BlockNumber
@@ -748,7 +758,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
     {
       NamedRegionTimer T("combine_lt", "DAG Combining after legalize types",
                          GroupName, GroupDescription, TimePassesIsEnabled);
-      CurDAG->Combine(AfterLegalizeTypes, *AA, OptLevel);
+      CurDAG->Combine(AfterLegalizeTypes, AA, OptLevel);
     }
 
     DEBUG(dbgs() << "Optimized type-legalized selection DAG: BB#" << BlockNumber
@@ -782,7 +792,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
     {
       NamedRegionTimer T("combine_lv", "DAG Combining after legalize vectors",
                          GroupName, GroupDescription, TimePassesIsEnabled);
-      CurDAG->Combine(AfterLegalizeVectorOps, *AA, OptLevel);
+      CurDAG->Combine(AfterLegalizeVectorOps, AA, OptLevel);
     }
 
     DEBUG(dbgs() << "Optimized vector-legalized selection DAG: BB#"
@@ -808,7 +818,7 @@ void SelectionDAGISel::CodeGenAndEmitDAG() {
   {
     NamedRegionTimer T("combine2", "DAG Combining 2", GroupName,
                        GroupDescription, TimePassesIsEnabled);
-    CurDAG->Combine(AfterLegalizeDAG, *AA, OptLevel);
+    CurDAG->Combine(AfterLegalizeDAG, AA, OptLevel);
   }
 
   DEBUG(dbgs() << "Optimized legalized selection DAG: BB#" << BlockNumber