From: Sanjoy Das <sanjoy@playingwithpointers.com>
Date: Sun, 2 Oct 2016 00:09:49 +0000 (+0000)
Subject: [ConstantRange] Make getEquivalentICmp smarter
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=4e4cf39e4619c3de2ec9fc7a5353e49ca5ee7d45;p=llvm

[ConstantRange] Make getEquivalentICmp smarter

This change teaches getEquivalentICmp to be smarter about generating
ICMP_NE and ICMP_EQ predicates.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283057 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/IR/ConstantRange.cpp b/lib/IR/ConstantRange.cpp
index 0f5c7128f3d..0dbefc7b0c2 100644
--- a/lib/IR/ConstantRange.cpp
+++ b/lib/IR/ConstantRange.cpp
@@ -147,6 +147,14 @@ bool ConstantRange::getEquivalentICmp(CmpInst::Predicate &Pred,
     Pred = isEmptySet() ? CmpInst::ICMP_ULT : CmpInst::ICMP_UGE;
     RHS = APInt(getBitWidth(), 0);
     Success = true;
+  } else if (auto *OnlyElt = getSingleElement()) {
+    Pred = CmpInst::ICMP_EQ;
+    RHS = *OnlyElt;
+    Success = true;
+  } else if (auto *OnlyMissingElt = inverse().getSingleElement()) {
+    Pred = CmpInst::ICMP_NE;
+    RHS = *OnlyMissingElt;
+    Success = true;
   } else if (getLower().isMinSignedValue() || getLower().isMinValue()) {
     Pred =
         getLower().isMinSignedValue() ? CmpInst::ICMP_SLT : CmpInst::ICMP_ULT;
diff --git a/unittests/IR/ConstantRangeTest.cpp b/unittests/IR/ConstantRangeTest.cpp
index f7a8a82043b..423f0627917 100644
--- a/unittests/IR/ConstantRangeTest.cpp
+++ b/unittests/IR/ConstantRangeTest.cpp
@@ -760,6 +760,37 @@ TEST(ConstantRange, GetEquivalentICmp) {
   EXPECT_FALSE(ConstantRange(APInt::getMinValue(32) - APInt(32, 100),
                              APInt::getMinValue(32) + APInt(32, 100))
                    .getEquivalentICmp(Pred, RHS));
+
+  EXPECT_TRUE(ConstantRange(APInt(32, 100)).getEquivalentICmp(Pred, RHS));
+  EXPECT_EQ(Pred, CmpInst::ICMP_EQ);
+  EXPECT_EQ(RHS, APInt(32, 100));
+
+  EXPECT_TRUE(
+      ConstantRange(APInt(32, 100)).inverse().getEquivalentICmp(Pred, RHS));
+  EXPECT_EQ(Pred, CmpInst::ICMP_NE);
+  EXPECT_EQ(RHS, APInt(32, 100));
+
+  // NB!  It would be correct for the following four calls to getEquivalentICmp
+  // to return ordered predicates like CmpInst::ICMP_ULT or CmpInst::ICMP_UGT.
+  // However, that's not the case today.
+
+  EXPECT_TRUE(ConstantRange(APInt(32, 0)).getEquivalentICmp(Pred, RHS));
+  EXPECT_EQ(Pred, CmpInst::ICMP_EQ);
+  EXPECT_EQ(RHS, APInt(32, 0));
+
+  EXPECT_TRUE(
+      ConstantRange(APInt(32, 0)).inverse().getEquivalentICmp(Pred, RHS));
+  EXPECT_EQ(Pred, CmpInst::ICMP_NE);
+  EXPECT_EQ(RHS, APInt(32, 0));
+
+  EXPECT_TRUE(ConstantRange(APInt(32, -1)).getEquivalentICmp(Pred, RHS));
+  EXPECT_EQ(Pred, CmpInst::ICMP_EQ);
+  EXPECT_EQ(RHS, APInt(32, -1));
+
+  EXPECT_TRUE(
+      ConstantRange(APInt(32, -1)).inverse().getEquivalentICmp(Pred, RHS));
+  EXPECT_EQ(Pred, CmpInst::ICMP_NE);
+  EXPECT_EQ(RHS, APInt(32, -1));
 }
 
 }  // anonymous namespace