Refactor code used in InstCombine::FoldAndOfICmps to new file.

This will be used by SimplifyCfg in a later commit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146803 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 66 insertions, 0 deletions

diff --git a/include/llvm/Transforms/Utils/CmpInstAnalysis.h b/include/llvm/Transforms/Utils/CmpInstAnalysis.h
new file mode 100644
index 0000000000..7ad7bddce5
--- /dev/null
+++ b/include/llvm/Transforms/Utils/CmpInstAnalysis.h
@@ -0,0 +1,66 @@
+//===-- CmpInstAnalysis.h - Utils to help fold compare insts ------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file holds routines to help analyse compare instructions
+// and fold them into constants or other compare instructions
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_UTILS_CMPINSTANALYSIS_H
+#define LLVM_TRANSFORMS_UTILS_CMPINSTANALYSIS_H
+
+#include "llvm/InstrTypes.h"
+
+namespace llvm {
+  class ICmpInst;
+  class Value;
+
+  /// getICmpCode - Encode a icmp predicate into a three bit mask.  These bits
+  /// are carefully arranged to allow folding of expressions such as:
+  ///
+  ///      (A < B) | (A > B) --> (A != B)
+  ///
+  /// Note that this is only valid if the first and second predicates have the
+  /// same sign. Is illegal to do: (A u< B) | (A s> B)
+  ///
+  /// Three bits are used to represent the condition, as follows:
+  ///   0  A > B
+  ///   1  A == B
+  ///   2  A < B
+  ///
+  /// <=>  Value  Definition
+  /// 000     0   Always false
+  /// 001     1   A >  B
+  /// 010     2   A == B
+  /// 011     3   A >= B
+  /// 100     4   A <  B
+  /// 101     5   A != B
+  /// 110     6   A <= B
+  /// 111     7   Always true
+  ///
+  unsigned getICmpCode(const ICmpInst *ICI, bool InvertPred = false);
+
+  /// getICmpValue - This is the complement of getICmpCode, which turns an
+  /// opcode and two operands into either a constant true or false, or the
+  /// predicate for a new ICmp instruction. The sign is passed in to determine
+  /// which kind of predicate to use in the new icmp instruction.
+  /// Non-NULL return value will be a true or false constant.
+  /// NULL return means a new ICmp is needed.  The predicate for which is
+  /// output in NewICmpPred.
+  Value *getICmpValue(bool Sign, unsigned Code, Value *LHS, Value *RHS,
+                      CmpInst::Predicate &NewICmpPred);
+
+  /// PredicatesFoldable - Return true if both predicates match sign or if at
+  /// least one of them is an equality comparison (which is signless).
+  bool PredicatesFoldable(CmpInst::Predicate p1, CmpInst::Predicate p2);
+
+} // end namespace llvm
+
+#endif
+