[PATCH] [SCEV] Revert bailout added in r75511.

[Sanjoy Das]

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D8624

Files:
  llvm/trunk/lib/Analysis/ScalarEvolution.cpp
  llvm/trunk/test/Analysis/ScalarEvolution/ext-antecedent.ll

Index: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp
@@ -6793,15 +6793,6 @@
   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;
@@ -6813,9 +6804,17 @@
   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());
Index: llvm/trunk/test/Analysis/ScalarEvolution/ext-antecedent.ll
===================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/ext-antecedent.ll
+++ llvm/trunk/test/Analysis/ScalarEvolution/ext-antecedent.ll
@@ -0,0 +1,45 @@
+; 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
+}

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