[IR][PatternMatch] introduce m_Unless() matcher

Summary:
I don't think it already exists? I don't see it at least.
It is important to have it because else we'll do some checks after `match()`,
and that may result in missed folds in commutative nodes.

Reviewers: spatel, craig.topper, RKSimon, majnemer

Reviewed By: spatel

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64037

llvm-svn: 367016

2 files changed, 30 insertions, 0 deletions

diff --git a/llvm/include/llvm/IR/PatternMatch.h b/llvm/include/llvm/IR/PatternMatch.h
index b6b2fa88f5b..f39678347d3 100644
--- a/llvm/include/llvm/IR/PatternMatch.h
+++ b/llvm/include/llvm/IR/PatternMatch.h
@@ -88,6 +88,20 @@ inline class_match<UndefValue> m_Undef() { return class_match<UndefValue>(); }
 /// Match an arbitrary Constant and ignore it.
 inline class_match<Constant> m_Constant() { return class_match<Constant>(); }
 
+/// Inverting matcher
+template <typename Ty> struct match_unless {
+  Ty M;
+
+  match_unless(const Ty &Matcher) : M(Matcher) {}
+
+  template <typename ITy> bool match(ITy *V) { return !M.match(V); }
+};
+
+/// Match if the inner matcher does *NOT* match.
+template <typename Ty> inline match_unless<Ty> m_Unless(const Ty &M) {
+  return match_unless<Ty>(M);
+}
+
 /// Matching combinators
 template <typename LTy, typename RTy> struct match_combine_or {
   LTy L;
diff --git a/llvm/unittests/IR/PatternMatch.cpp b/llvm/unittests/IR/PatternMatch.cpp
index 600494fba26..8263acb59a0 100644
--- a/llvm/unittests/IR/PatternMatch.cpp
+++ b/llvm/unittests/IR/PatternMatch.cpp
@@ -454,6 +454,22 @@ TEST_F(PatternMatchTest, SpecificIntSLE) {
           .match(NegOne));
 }
 
+TEST_F(PatternMatchTest, Unless) {
+  Value *X = IRB.CreateAdd(IRB.getInt32(1), IRB.getInt32(0));
+
+  EXPECT_TRUE(m_Add(m_One(), m_Zero()).match(X));
+  EXPECT_FALSE(m_Add(m_Zero(), m_One()).match(X));
+
+  EXPECT_FALSE(m_Unless(m_Add(m_One(), m_Zero())).match(X));
+  EXPECT_TRUE(m_Unless(m_Add(m_Zero(), m_One())).match(X));
+
+  EXPECT_TRUE(m_c_Add(m_One(), m_Zero()).match(X));
+  EXPECT_TRUE(m_c_Add(m_Zero(), m_One()).match(X));
+
+  EXPECT_FALSE(m_Unless(m_c_Add(m_One(), m_Zero())).match(X));
+  EXPECT_FALSE(m_Unless(m_c_Add(m_Zero(), m_One())).match(X));
+}
+
 TEST_F(PatternMatchTest, CommutativeDeferredValue) {
   Value *X = IRB.getInt32(1);
   Value *Y = IRB.getInt32(2);