[PATCH] D40953: [SCEV] Fix predicate usage in computeExitLimitFromICmp

[Max Kazantsev via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL320142: [SCEV] Fix predicate usage in computeExitLimitFromICmp (authored by mkazantsev).

Changed prior to commit:
  https://reviews.llvm.org/D40953?vs=125943&id=126123#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D40953

Files:
  llvm/trunk/lib/Analysis/ScalarEvolution.cpp
  llvm/trunk/test/Analysis/ScalarEvolution/shift-op.ll


Index: llvm/trunk/test/Analysis/ScalarEvolution/shift-op.ll
===================================================================
--- llvm/trunk/test/Analysis/ScalarEvolution/shift-op.ll
+++ llvm/trunk/test/Analysis/ScalarEvolution/shift-op.ll
@@ -160,5 +160,24 @@
   ret void
 }
 
+define void @test9() {
+; CHECK-LABEL: Determining loop execution counts for: @test9
+; CHECK: Loop %loop: Unpredictable max backedge-taken count.
+
+; This is an infinite loop, make sure that it recognized as such.
+
+entry:
+  br label %loop
+
+leave:
+  ret void
+
+loop:
+  %iv = phi i32 [ -20, %entry ], [ %iv.shift, %loop ]
+  %iv.shift = ashr i32 %iv, 1
+  %exit.cond = icmp sgt i32 %iv, -1
+  br i1 %exit.cond, label %leave, label %loop
+}
+
 !0 = !{i32 0, i32 50000}
 !1 = !{i32 -5000, i32 -1}
Index: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp
@@ -7074,6 +7074,7 @@
     Cond = ExitCond->getPredicate();
   else
     Cond = ExitCond->getInversePredicate();
+  const ICmpInst::Predicate OriginalCond = Cond;
 
   // Handle common loops like: for (X = "string"; *X; ++X)
   if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
@@ -7157,7 +7158,7 @@
     return ExhaustiveCount;
 
   return computeShiftCompareExitLimit(ExitCond->getOperand(0),
-                                      ExitCond->getOperand(1), L, Cond);
+                                      ExitCond->getOperand(1), L, OriginalCond);
 }
 
 ScalarEvolution::ExitLimit


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