From: Dan Gohman <gohman@apple.com>
Date: Mon, 16 Aug 2010 15:50:00 +0000 (+0000)
Subject: Instead of having CollectSubexpr's categorize operands as interesting or
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=3e22b7c91698f55b9053e88a168bd9e2eed71c9b;p=oota-llvm.git

Instead of having CollectSubexpr's categorize operands as interesting or
uninteresting, just put all the operands on one list and make
GenerateReassociations make the decision about what's interesting.
This is simpler, and it avoids an extra ScalarEvolution::getAddExpr call.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111133 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 95e25dd76c9..f7b67113bd8 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -2230,14 +2230,13 @@ LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
 /// separate registers. If C is non-null, multiply each subexpression by C.
 static void CollectSubexprs(const SCEV *S, const SCEVConstant *C,
                             SmallVectorImpl<const SCEV *> &Ops,
-                            SmallVectorImpl<const SCEV *> &UninterestingOps,
                             const Loop *L,
                             ScalarEvolution &SE) {
   if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
     // Break out add operands.
     for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
          I != E; ++I)
-      CollectSubexprs(*I, C, Ops, UninterestingOps, L, SE);
+      CollectSubexprs(*I, C, Ops, L, SE);
     return;
   } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
     // Split a non-zero base out of an addrec.
@@ -2245,8 +2244,8 @@ static void CollectSubexprs(const SCEV *S, const SCEVConstant *C,
       CollectSubexprs(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
                                        AR->getStepRecurrence(SE),
                                        AR->getLoop()),
-                      C, Ops, UninterestingOps, L, SE);
-      CollectSubexprs(AR->getStart(), C, Ops, UninterestingOps, L, SE);
+                      C, Ops, L, SE);
+      CollectSubexprs(AR->getStart(), C, Ops, L, SE);
       return;
     }
   } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
@@ -2256,17 +2255,13 @@ static void CollectSubexprs(const SCEV *S, const SCEVConstant *C,
             dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
         CollectSubexprs(Mul->getOperand(1),
                         C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0,
-                        Ops, UninterestingOps, L, SE);
+                        Ops, L, SE);
         return;
       }
   }
 
-  // Otherwise use the value itself. Loop-variant "unknown" values are
-  // uninteresting; we won't be able to do anything meaningful with them.
-  if (!C && isa<SCEVUnknown>(S) && !S->isLoopInvariant(L))
-    UninterestingOps.push_back(S);
-  else
-    Ops.push_back(C ? SE.getMulExpr(C, S) : S);
+  // Otherwise use the value itself, optionally with a scale applied.
+  Ops.push_back(C ? SE.getMulExpr(C, S) : S);
 }
 
 /// GenerateReassociations - Split out subexpressions from adds and the bases of
@@ -2280,19 +2275,19 @@ void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
   for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
     const SCEV *BaseReg = Base.BaseRegs[i];
 
-    SmallVector<const SCEV *, 8> AddOps, UninterestingAddOps;
-    CollectSubexprs(BaseReg, 0, AddOps, UninterestingAddOps, L, SE);
-
-    // Add any uninteresting values as one register, as we won't be able to
-    // form any interesting reassociation opportunities with them. They'll
-    // just have to be added inside the loop no matter what we do.
-    if (!UninterestingAddOps.empty())
-      AddOps.push_back(SE.getAddExpr(UninterestingAddOps));
+    SmallVector<const SCEV *, 8> AddOps;
+    CollectSubexprs(BaseReg, 0, AddOps, L, SE);
 
     if (AddOps.size() == 1) continue;
 
     for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
          JE = AddOps.end(); J != JE; ++J) {
+
+      // Loop-variant "unknown" values are uninteresting; we won't be able to
+      // do anything meaningful with them.
+      if (isa<SCEVUnknown>(*J) && !(*J)->isLoopInvariant(L))
+        continue;
+
       // Don't pull a constant into a register if the constant could be folded
       // into an immediate field.
       if (isAlwaysFoldable(*J, LU.MinOffset, LU.MaxOffset,