Switch the SCEV expander and LoopStrengthReduce to use

TargetTransformInfo rather than TargetLowering, removing one of the
primary instances of the layering violation of Transforms depending
directly on Target.

This is a really big deal because LSR used to be a "special" pass that
could only be tested fully using llc and by looking at the full output
of it. It also couldn't run with any other loop passes because it had to
be created by the backend. No longer is this true. LSR is now just
a normal pass and we should probably lift the creation of LSR out of
lib/CodeGen/Passes.cpp and into the PassManagerBuilder. =] I've not done
this, or updated all of the tests to use opt and a triple, because
I suspect someone more familiar with LSR would do a better job. This
change should be essentially without functional impact for normal
compilations, and only change behvaior of targetless compilations.

The conversion required changing all of the LSR code to refer to the TTI
interfaces, which fortunately are very similar to TargetLowering's
interfaces. However, it also allowed us to *always* expect to have some
implementation around. I've pushed that simplification through the pass,
and leveraged it to simplify code somewhat. It required some test
updates for one of two things: either we used to skip some checks
altogether but now we get the default "no" answer for them, or we used
to have no information about the target and now we do have some.

I've also started the process of removing AddrMode, as the TTI interface
doesn't use it any longer. In some cases this simplifies code, and in
others it adds some complexity, but I think it's not a bad tradeoff even
there. Subsequent patches will try to clean this up even further and use
other (more appropriate) abstractions.

Yet again, almost all of the formatting changes brought to you by
clang-format. =]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171735 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 8 insertions, 6 deletions

diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp
index 5f0ba2e..b87ad75 100644
--- a/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -16,11 +16,11 @@
 #include "llvm/Analysis/ScalarEvolutionExpander.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/Support/Debug.h"
-#include "llvm/Target/TargetLowering.h"
 
 using namespace llvm;
 
@@ -1600,14 +1600,14 @@ static bool width_descending(Value *lhs, Value *rhs) {
 /// the same context that SCEVExpander is used.
 unsigned SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
                                            SmallVectorImpl<WeakVH> &DeadInsts,
-                                           const TargetLowering *TLI) {
+                                           const TargetTransformInfo *TTI) {
   // Find integer phis in order of increasing width.
   SmallVector<PHINode*, 8> Phis;
   for (BasicBlock::iterator I = L->getHeader()->begin();
        PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
     Phis.push_back(Phi);
   }
-  if (TLI)
+  if (TTI)
     std::sort(Phis.begin(), Phis.end(), width_descending);
 
   unsigned NumElim = 0;
@@ -1635,8 +1635,8 @@ unsigned SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
     PHINode *&OrigPhiRef = ExprToIVMap[SE.getSCEV(Phi)];
     if (!OrigPhiRef) {
       OrigPhiRef = Phi;
-      if (Phi->getType()->isIntegerTy() && TLI
-          && TLI->isTruncateFree(Phi->getType(), Phis.back()->getType())) {
+      if (Phi->getType()->isIntegerTy() && TTI
+          && TTI->isTruncateFree(Phi->getType(), Phis.back()->getType())) {
         // This phi can be freely truncated to the narrowest phi type. Map the
         // truncated expression to it so it will be reused for narrow types.
         const SCEV *TruncExpr =
diff --git a/lib/Analysis/TargetTransformInfo.cpp b/lib/Analysis/TargetTransformInfo.cpp
index 0299373..63f495a 100644
--- a/lib/Analysis/TargetTransformInfo.cpp
+++ b/lib/Analysis/TargetTransformInfo.cpp
@@ -179,7 +179,9 @@ struct NoTTI : ImmutablePass, TargetTransformInfo {
 
   bool isLegalAddressingMode(Type *Ty, GlobalValue *BaseGV, int64_t BaseOffset,
                              bool HasBaseReg, int64_t Scale) const {
-    return false;
+    // Guess that reg+reg addressing is allowed. This heuristic is taken from
+    // the implementation of LSR.
+    return !BaseGV && BaseOffset == 0 && Scale <= 1;
   }
 
   bool isTruncateFree(Type *Ty1, Type *Ty2) const {