Fix the order that SCEVExpander considers add operands in so that

it doesn't miss an opportunity to form a GEP, regardless of the
relative loop depths of the operands. This fixes rdar://8197217.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108475 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 54 insertions, 2 deletions

diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp
index d4a4b26..0f3e33f 100644
--- a/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -647,6 +647,11 @@ public:
 
   bool operator()(std::pair<const Loop *, const SCEV *> LHS,
                   std::pair<const Loop *, const SCEV *> RHS) const {
+    // Keep pointer operands sorted at the end.
+    if (LHS.second->getType()->isPointerTy() !=
+        RHS.second->getType()->isPointerTy())
+      return LHS.second->getType()->isPointerTy();
+
     // Compare loops with PickMostRelevantLoop.
     if (LHS.first != RHS.first)
       return PickMostRelevantLoop(LHS.first, RHS.first, DT) != LHS.first;
@@ -699,8 +704,15 @@ Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) {
       // The running sum expression is a pointer. Try to form a getelementptr
       // at this level with that as the base.
       SmallVector<const SCEV *, 4> NewOps;
-      for (; I != E && I->first == CurLoop; ++I)
-        NewOps.push_back(I->second);
+      for (; I != E && I->first == CurLoop; ++I) {
+        // If the operand is SCEVUnknown and not instructions, peek through
+        // it, to enable more of it to be folded into the GEP.
+        const SCEV *X = I->second;
+        if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(X))
+          if (!isa<Instruction>(U->getValue()))
+            X = SE.getSCEV(U->getValue());
+        NewOps.push_back(X);
+      }
       Sum = expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, Sum);
     } else if (const PointerType *PTy = dyn_cast<PointerType>(Op->getType())) {
       // The running sum is an integer, and there's a pointer at this level.
diff --git a/test/Transforms/IndVarSimplify/uglygep.ll b/test/Transforms/IndVarSimplify/uglygep.ll
new file mode 100644
index 0000000..469b7c0
--- /dev/null
+++ b/test/Transforms/IndVarSimplify/uglygep.ll
@@ -0,0 +1,40 @@
+; RUN: opt -indvars -S | not grep uglygep
+; rdar://8197217
+
+; Indvars should be able to emit a clean GEP here, not an uglygep.
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
+target triple = "x86_64-apple-darwin11.0"
+
+@numf2s = external global i32                     ; <i32*> [#uses=1]
+@numf1s = external global i32                     ; <i32*> [#uses=1]
+@tds = external global double**                   ; <double***> [#uses=1]
+
+define void @init_td(i32 %tmp7) nounwind {
+entry:
+  br label %bb4
+
+bb4:                                              ; preds = %bb3, %entry
+  %i.0 = phi i32 [ 0, %entry ], [ %tmp9, %bb3 ]   ; <i32> [#uses=3]
+  br label %bb
+
+bb:                                               ; preds = %bb4
+  br label %bb2
+
+bb2:                                              ; preds = %bb1, %bb
+  %j.0 = phi i32 [ 0, %bb ], [ %tmp6, %bb1 ]      ; <i32> [#uses=3]
+  %tmp8 = icmp slt i32 %j.0, %tmp7                ; <i1> [#uses=1]
+  br i1 %tmp8, label %bb1, label %bb3
+
+bb1:                                              ; preds = %bb2
+  %tmp = load double*** @tds, align 8             ; <double**> [#uses=1]
+  %tmp1 = sext i32 %i.0 to i64                    ; <i64> [#uses=1]
+  %tmp2 = getelementptr inbounds double** %tmp, i64 %tmp1 ; <double**> [#uses=1]
+  %tmp3 = load double** %tmp2, align 1            ; <double*> [#uses=1]
+  %tmp6 = add nsw i32 %j.0, 1                     ; <i32> [#uses=1]
+  br label %bb2
+
+bb3:                                              ; preds = %bb2
+  %tmp9 = add nsw i32 %i.0, 1                     ; <i32> [#uses=1]
+  br label %bb4
+}