[PATCH] D88015: [SCEV] Support unsigned predicates in isKnownPredicateViaNoOverflow

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev updated this revision to Diff 293396.
mkazantsev added a comment.

Reloaded with dedicated unit test to make it independent on underlying patches (the only dependency was test).


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D88015/new/

https://reviews.llvm.org/D88015

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp
  llvm/unittests/Analysis/ScalarEvolutionTest.cpp


Index: llvm/unittests/Analysis/ScalarEvolutionTest.cpp
===================================================================
--- llvm/unittests/Analysis/ScalarEvolutionTest.cpp
+++ llvm/unittests/Analysis/ScalarEvolutionTest.cpp
@@ -1165,4 +1165,25 @@
               cast<SCEVAddRecExpr>(ScevIV)->getStepRecurrence(SE));
   });
 }
+
+TEST_F(ScalarEvolutionsTest, SCEVAddNUW) {
+  LLVMContext C;
+  SMDiagnostic Err;
+  std::unique_ptr<Module> M = parseAssemblyString("define void @foo(i32 %x) { "
+                                                  "  ret void "
+                                                  "} ",
+                                                  Err, C);
+
+  ASSERT_TRUE(M && "Could not parse module?");
+  ASSERT_TRUE(!verifyModule(*M) && "Must have been well formed!");
+
+  runWithSE(*M, "foo", [](Function &F, LoopInfo &LI, ScalarEvolution &SE) {
+    auto *X = SE.getSCEV(getArgByName(F, "x"));
+    auto *One = SE.getOne(X->getType());
+    auto *Sum = SE.getAddExpr(X, One, SCEV::FlagNUW);
+    EXPECT_TRUE(SE.isKnownPredicate(ICmpInst::ICMP_UGE, Sum, X));
+    EXPECT_TRUE(SE.isKnownPredicate(ICmpInst::ICMP_UGT, Sum, X));
+  });
+}
+
 }  // end namespace llvm
Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -9314,6 +9314,24 @@
     if (MatchBinaryAddToConst(LHS, RHS, C, SCEV::FlagNSW) && C.isNegative())
       return true;
     break;
+
+  case ICmpInst::ICMP_UGE:
+    std::swap(LHS, RHS);
+    LLVM_FALLTHROUGH;
+  case ICmpInst::ICMP_ULE:
+    // X u<= (X + C)<nuw> for any C
+    if (MatchBinaryAddToConst(RHS, LHS, C, SCEV::FlagNUW))
+      return true;
+    break;
+
+  case ICmpInst::ICMP_UGT:
+    std::swap(LHS, RHS);
+    LLVM_FALLTHROUGH;
+  case ICmpInst::ICMP_ULT:
+    // X u< (X + C)<nuw> if C != 0
+    if (MatchBinaryAddToConst(RHS, LHS, C, SCEV::FlagNUW) && !C.isNullValue())
+      return true;
+    break;
   }
 
   return false;


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