[SCEV] Revert bailout added in r75511.

[sanjoy]

Summary

With the introduction of MarkPendingLoopPredicates in r157092, I don't
think the bailout is needed anymore.

[atrick]

Thanks, that makes sense. I'm somewhat taking your word for it.

lib/Analysis/ScalarEvolution.cpp

if (BO->getOpcode() == Instruction::And) {
         return isImpliedCond(Pred, LHS, RHS, BO->getOperand(0), Inverse) ||
                isImpliedCond(Pred, LHS, RHS, BO->getOperand(1), Inverse);
     }
   }
 
   ICmpInst *ICI = dyn_cast<ICmpInst>(FoundCondValue);
   if (!ICI) return false;
 
-  // Bail if the ICmp's operands' types are wider than the needed type
-  // before attempting to call getSCEV on them. This avoids infinite
-  // recursion, since the analysis of widening casts can require loop
-  // exit condition information for overflow checking, which would
-  // lead back here.
-  if (getTypeSizeInBits(LHS->getType()) <
-      getTypeSizeInBits(ICI->getOperand(0)->getType()))
-    return false;
-
   // Now that we found a conditional branch that dominates the loop or controls
   // the loop latch. Check to see if it is the comparison we are looking for.
   ICmpInst::Predicate FoundPred;
   if (Inverse)
     FoundPred = ICI->getInversePredicate();
   else
     FoundPred = ICI->getPredicate();
 
   const SCEV *FoundLHS = getSCEV(ICI->getOperand(0));
   const SCEV *FoundRHS = getSCEV(ICI->getOperand(1));
 
-  // Balance the types. The case where FoundLHS' type is wider than
-  // LHS' type is checked for above.
-  if (getTypeSizeInBits(LHS->getType()) >
+  // Balance the types.
+  if (getTypeSizeInBits(LHS->getType()) <
+      getTypeSizeInBits(FoundLHS->getType())) {
+    if (CmpInst::isSigned(Pred)) {
+      LHS = getSignExtendExpr(LHS, FoundLHS->getType());
+      RHS = getSignExtendExpr(RHS, FoundLHS->getType());
+    } else {
+      LHS = getZeroExtendExpr(LHS, FoundLHS->getType());
+      RHS = getZeroExtendExpr(RHS, FoundLHS->getType());
+    }
+  } else if (getTypeSizeInBits(LHS->getType()) >
       getTypeSizeInBits(FoundLHS->getType())) {
     if (CmpInst::isSigned(FoundPred)) {
       FoundLHS = getSignExtendExpr(FoundLHS, LHS->getType());
       FoundRHS = getSignExtendExpr(FoundRHS, LHS->getType());
     } else {
       FoundLHS = getZeroExtendExpr(FoundLHS, LHS->getType());
       FoundRHS = getZeroExtendExpr(FoundRHS, LHS->getType());
     }

test/Analysis/ScalarEvolution/ext-antecedent.ll

+; RUN: opt -S -indvars < %s | FileCheck %s
+
+declare void @use(i1)
+
+define void @sext_condition(i8 %t) {
+; CHECK-LABEL: sext_condition
+ entry:
+  %st = sext i8 %t to i16
+  %ecmp = icmp slt i16 %st, 42
+  br i1 %ecmp, label %loop, label %exit
+
+ loop:
+; CHECK-LABEL: loop
+  %idx = phi i8 [ %t, %entry ], [ %idx.inc, %loop ]
+  %idx.inc = add i8 %idx, 1
+  %c = icmp slt i8 %idx, 42
+; CHECK: call void @use(i1 true)
+  call void @use(i1 %c)
+  %be = icmp slt i8 %idx.inc, 42
+  br i1 %be, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @zext_condition(i8 %t) {
+; CHECK-LABEL: zext_condition
+ entry:
+  %st = zext i8 %t to i16
+  %ecmp = icmp ult i16 %st, 42
+  br i1 %ecmp, label %loop, label %exit
+
+ loop:
+; CHECK-LABEL: loop
+  %idx = phi i8 [ %t, %entry ], [ %idx.inc, %loop ]
+  %idx.inc = add i8 %idx, 1
+  %c = icmp ult i8 %idx, 42
+; CHECK: call void @use(i1 true)
+  call void @use(i1 %c)
+  %be = icmp ult i8 %idx.inc, 42
+  br i1 %be, label %loop, label %exit
+
+ exit:
+  ret void
+}