revert 325687

[evstupac]

Summary

reverting temporary fix:
https://bugs.llvm.org/show_bug.cgi?id=36032#c12

[sbaranga]

LGTM, thanks!

llvm/trunk/lib/Analysis/ScalarEvolution.cpp

MaxExtDepth("scalar-evolution-max-ext-depth", cl::Hidden,
                 cl::desc("Maximum depth of recursive SExt/ZExt"),
                 cl::init(8));
 
 static cl::opt<unsigned>
     MaxAddRecSize("scalar-evolution-max-add-rec-size", cl::Hidden,
                   cl::desc("Max coefficients in AddRec during evolving"),
                   cl::init(16));
 
-static cl::opt<bool> VersionUnknown(
-    "scev-version-unknown", cl::Hidden,
-    cl::desc("Use predicated scalar evolution to version SCEVUnknowns"),
-    cl::init(false));
-
 //===----------------------------------------------------------------------===//
 //                           SCEV class definitions
 //===----------------------------------------------------------------------===//
 
 //===----------------------------------------------------------------------===//
 // Implementation of the SCEV class.
 //
 
private:
 
   // If \p Expr represents a PHINode, we try to see if it can be represented
   // as an AddRec, possibly under a predicate (PHISCEVPred). If it is possible
   // to add this predicate as a runtime overflow check, we return the AddRec.
   // If \p Expr does not meet these conditions (is not a PHI node, or we
   // couldn't create an AddRec for it, or couldn't add the predicate), we just
   // return \p Expr.
   const SCEV *convertToAddRecWithPreds(const SCEVUnknown *Expr) {
-    if (!VersionUnknown)
-      return Expr;
     if (!isa<PHINode>(Expr->getValue()))
       return Expr;
     Optional<std::pair<const SCEV *, SmallVector<const SCEVPredicate *, 3>>>
     PredicatedRewrite = SE.createAddRecFromPHIWithCasts(Expr);
     if (!PredicatedRewrite)
       return Expr;
     for (auto *P : PredicatedRewrite->second){
       // Wrap predicates from outer loops are not supported.

llvm/trunk/test/Transforms/LoopVectorize/X86/pr36524.ll

-; RUN: opt -S -scev-version-unknown -loop-vectorize -force-vector-width=4 -force-vector-interleave=1 < %s | FileCheck %s
+; RUN: opt -S -loop-vectorize -force-vector-width=4 -force-vector-interleave=1 < %s | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128-ni:1"
 
 define void @foo() {
 ; CHECK-LABEL: @foo(
 ; CHECK:       vector.body:
 ; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH:%.*]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY:%.*]] ]
 ; CHECK-NEXT:    [[VEC_IND:%.*]] = phi <4 x i64> [ <i64 2, i64 3, i64 4, i64 5>, [[VECTOR_PH]] ], [ [[VEC_IND_NEXT:%.*]], [[VECTOR_BODY]] ]

llvm/trunk/test/Transforms/LoopVectorize/pr30654-phiscev-sext-trunc.ll

-; RUN: opt -S -loop-vectorize -force-vector-width=4 -force-vector-interleave=1 -scev-version-unknown < %s 2>&1 | FileCheck %s
+; RUN: opt -S -loop-vectorize -force-vector-width=4 -force-vector-interleave=1 < %s 2>&1 | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 ; Check that the vectorizer identifies the %p.09 phi,
 ; as an induction variable, despite the potential overflow
 ; due to the truncation from 32bit to 8bit. 
 ; SCEV will detect the pattern "sext(trunc(%p.09)) + %step"
 ; and generate the required runtime checks under which

llvm/trunk/test/Transforms/LoopVectorize/pr35773.ll

-; RUN: opt -S -loop-vectorize -force-vector-width=4 -force-vector-interleave=1 -scev-version-unknown < %s 2>&1 | FileCheck %s
+; RUN: opt -S -loop-vectorize -force-vector-width=4 -force-vector-interleave=1 < %s 2>&1 | FileCheck %s
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 @a = common local_unnamed_addr global i32 0, align 4
 @b = common local_unnamed_addr global i8 0, align 1
 
 ; Function Attrs: norecurse nounwind uwtable
 define void @doit1() local_unnamed_addr{
 entry:
   br label %for.body

llvm/trunk/test/Transforms/LoopVectorize/vect-phiscev-sext-trunc.ll

-; RUN: opt -S -loop-vectorize -force-vector-width=8 -force-vector-interleave=1 -scev-version-unknown < %s | FileCheck %s -check-prefix=VF8
-; RUN: opt -S -loop-vectorize -force-vector-width=1 -force-vector-interleave=4 -scev-version-unknown < %s | FileCheck %s -check-prefix=VF1
+; RUN: opt -S -loop-vectorize -force-vector-width=8 -force-vector-interleave=1 < %s | FileCheck %s -check-prefix=VF8
+; RUN: opt -S -loop-vectorize -force-vector-width=1 -force-vector-interleave=4 < %s | FileCheck %s -check-prefix=VF1
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
 ; Given a loop with an induction variable which is being
 ; truncated/extended using casts that had been proven to
 ; be redundant under a runtime test, we want to make sure
 ; that these casts, do not get vectorized/scalarized/widened. 
 ; This is the case for inductions whose SCEV expression is