[SCEV] Make isLoopEntryGuardedByCond a bit smarter

Sometimes `isLoopEntryGuardedByCond` cannot prove predicate `a > b` directly.
But it is a common situation when `a >= b` is known from ranges and `a != b` is
known from a dominating condition. Thia patch teaches SCEV to sum these facts
together and prove strict comparison via non-strict one.

Differential Revision: https://reviews.llvm.org/D42835

llvm-svn: 324453

1 files changed, 13 insertions, 0 deletions

diff --git a/llvm/include/llvm/IR/InstrTypes.h b/llvm/include/llvm/IR/InstrTypes.h
index 871f702f95f..9e938a462cf 100644
--- a/llvm/include/llvm/IR/InstrTypes.h
+++ b/llvm/include/llvm/IR/InstrTypes.h
@@ -973,6 +973,19 @@ public:
   /// @brief Return the predicate as if the operands were swapped.
   static Predicate getSwappedPredicate(Predicate pred);
 
+  /// For example, SGT -> SGE, SLT -> SLE, ULT -> ULE, UGT -> UGE.
+  /// @brief Returns the non-strict version of strict comparisons.
+  Predicate getNonStrictPredicate() const {
+    return getNonStrictPredicate(getPredicate());
+  }
+
+  /// This is a static version that you can use without an instruction
+  /// available.
+  /// @returns the non-strict version of comparison provided in \p pred.
+  /// If \p pred is not a strict comparison predicate, returns \p pred.
+  /// @brief Returns the non-strict version of strict comparisons.
+  static Predicate getNonStrictPredicate(Predicate pred);
+
   /// @brief Provide more efficient getOperand methods.
   DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);