Remove LCSSA's bogus dependence on LoopSimplify and LoopSimplify's bogus

dependence on DominanceFrontier. Instead, add an explicit DominanceFrontier
pass in StandardPasses.h to ensure that it gets scheduled at the right
time.

Declare that loop unrolling preserves ScalarEvolution, and shuffle some
getAnalysisUsages.

This eliminates one LoopSimplify and one LCCSA run in the standard
compile opts sequence.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109413 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/StandardPasses.h

@@ -20,6 +20,7 @@
 #define LLVM_SUPPORT_STANDARDPASSES_H
 
 #include "llvm/PassManager.h"
+#include "llvm/Analysis/Dominators.h"
 #include "llvm/Analysis/Passes.h"
 #include "llvm/Analysis/Verifier.h"
 #include "llvm/Transforms/Scalar.h"
@@ -128,6 +129,8 @@ namespace llvm {
     PM->add(createTailCallEliminationPass());   // Eliminate tail calls
     PM->add(createCFGSimplificationPass());     // Merge & remove BBs
     PM->add(createReassociatePass());           // Reassociate expressions
+    // Explicitly schedule this to ensure that it runs before any loop pass.
+    PM->add(new DominanceFrontier());           // Calculate Dominance Frontiers
     PM->add(createLoopRotatePass());            // Rotate Loop
     PM->add(createLICMPass());                  // Hoist loop invariants
     PM->add(createLoopUnswitchPass(OptimizeSize || OptimizationLevel < 3));

lib/Transforms/Scalar/LoopDeletion.cpp

@@ -38,9 +38,9 @@ namespace {
                     bool &Changed, BasicBlock *Preheader);
 
     virtual void getAnalysisUsage(AnalysisUsage& AU) const {
-      AU.addRequired<ScalarEvolution>();
       AU.addRequired<DominatorTree>();
       AU.addRequired<LoopInfo>();
+      AU.addRequired<ScalarEvolution>();
       AU.addRequiredID(LoopSimplifyID);
       AU.addRequiredID(LCSSAID);
       

lib/Transforms/Scalar/LoopUnrollPass.cpp

@@ -17,6 +17,7 @@
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Analysis/LoopPass.h"
 #include "llvm/Analysis/InlineCost.h"
+#include "llvm/Analysis/ScalarEvolution.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
@@ -55,17 +56,19 @@ namespace {
     /// loop preheaders be inserted into the CFG...
     ///
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addRequired<LoopInfo>();
+      AU.addPreserved<LoopInfo>();
       AU.addRequiredID(LoopSimplifyID);
+      AU.addPreservedID(LoopSimplifyID);
       AU.addRequiredID(LCSSAID);
-      AU.addRequired<LoopInfo>();
       AU.addPreservedID(LCSSAID);
-      AU.addPreserved<LoopInfo>();
       // FIXME: Loop unroll requires LCSSA. And LCSSA requires dom info.
       // If loop unroll does not preserve dom info then LCSSA pass on next
       // loop will receive invalid dom info.
       // For now, recreate dom info, if loop is unrolled.
       AU.addPreserved<DominatorTree>();
       AU.addPreserved<DominanceFrontier>();
+      AU.addPreserved<ScalarEvolution>();
     }
   };
 }

lib/Transforms/Utils/LCSSA.cpp

@@ -64,17 +64,12 @@ namespace {
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
       AU.setPreservesCFG();
 
-      AU.addRequiredTransitive<DominatorTree>();
+      AU.addRequired<DominatorTree>();
       AU.addPreserved<DominatorTree>();
       AU.addPreserved<DominanceFrontier>();
-      AU.addRequiredTransitive<LoopInfo>();
+      AU.addRequired<LoopInfo>();
       AU.addPreserved<LoopInfo>();
-
-      // LCSSA doesn't actually require LoopSimplify, but the PassManager
-      // doesn't know how to schedule LoopSimplify by itself.
-      AU.addRequiredID(LoopSimplifyID);
       AU.addPreservedID(LoopSimplifyID);
-
       AU.addPreserved<ScalarEvolution>();
     }
   private:

lib/Transforms/Utils/LoopSimplify.cpp

@@ -77,22 +77,17 @@ namespace {
 
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
       // We need loop information to identify the loops...
-      AU.addRequiredTransitive<DominatorTree>();
+      AU.addRequired<DominatorTree>();
       AU.addPreserved<DominatorTree>();
 
-      // Request DominanceFrontier now, even though LoopSimplify does
-      // not use it. This allows Pass Manager to schedule Dominance
-      // Frontier early enough such that one LPPassManager can handle
-      // multiple loop transformation passes.
-      AU.addRequired<DominanceFrontier>();
-      AU.addPreserved<DominanceFrontier>();
-
-      AU.addRequiredTransitive<LoopInfo>();
+      AU.addRequired<LoopInfo>();
       AU.addPreserved<LoopInfo>();
 
       AU.addPreserved<AliasAnalysis>();
       AU.addPreserved<ScalarEvolution>();
       AU.addPreservedID(BreakCriticalEdgesID);  // No critical edges added.
+      AU.addPreserved<DominanceFrontier>();
+      AU.addPreservedID(LCSSAID);
     }
 
     /// verifyAnalysis() - Verify LoopSimplifyForm's guarantees.