From 365d729e1075a9391b7520306d8d9beee84d52b5 Mon Sep 17 00:00:00 2001
From: Roman Lebedev <lebedev.ri@gmail.com>
Date: Thu, 7 Nov 2019 01:19:54 +0300
Subject: [ConstantRange] Cleanup addWithNoWrap() by just piggybacking on
 sadd_sat()/uadd_sat()

As discussed in https://reviews.llvm.org/D69918
that happens to work as intended, and returns empty set if
there is always an overflow because we get lucky with intersection.
Since there's now an explicit test for that, let's prefer cleaner code.
---
 llvm/lib/IR/ConstantRange.cpp | 40 ++++++++--------------------------------
 1 file changed, 8 insertions(+), 32 deletions(-)

(limited to 'llvm/lib/IR/ConstantRange.cpp')

diff --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp
index 32235a11637..cc1d86ba1b1 100644
--- a/llvm/lib/IR/ConstantRange.cpp
+++ b/llvm/lib/IR/ConstantRange.cpp
@@ -864,41 +864,17 @@ ConstantRange ConstantRange::addWithNoWrap(const ConstantRange &Other,
   using OBO = OverflowingBinaryOperator;
   ConstantRange Result = add(Other);
 
-  auto addWithNoUnsignedWrap = [this](const ConstantRange &Other) {
-    APInt LMin = getUnsignedMin(), LMax = getUnsignedMax();
-    APInt RMin = Other.getUnsignedMin(), RMax = Other.getUnsignedMax();
-    bool Overflow;
-    APInt NewMin = LMin.uadd_ov(RMin, Overflow);
-    if (Overflow)
-      return getEmpty();
-    APInt NewMax = LMax.uadd_sat(RMax);
-    return getNonEmpty(std::move(NewMin), std::move(NewMax) + 1);
-  };
-
-  auto addWithNoSignedWrap = [this](const ConstantRange &Other) {
-    APInt LMin = getSignedMin(), LMax = getSignedMax();
-    APInt RMin = Other.getSignedMin(), RMax = Other.getSignedMax();
-    if (LMin.isNonNegative()) {
-      bool Overflow;
-      APInt Temp = LMin.sadd_ov(RMin, Overflow);
-      if (Overflow)
-        return getEmpty();
-    }
-    if (LMax.isNegative()) {
-      bool Overflow;
-      APInt Temp = LMax.sadd_ov(RMax, Overflow);
-      if (Overflow)
-        return getEmpty();
-    }
-    APInt NewMin = LMin.sadd_sat(RMin);
-    APInt NewMax = LMax.sadd_sat(RMax);
-    return getNonEmpty(std::move(NewMin), std::move(NewMax) + 1);
-  };
+  // If an overflow happens for every value pair in these two constant ranges,
+  // we must return Empty set. In this case, we get that for free, because we
+  // get lucky that intersection of add() with uadd_sat()/sadd_sat() results
+  // in an empty set.
 
   if (NoWrapKind & OBO::NoSignedWrap)
-    Result = Result.intersectWith(addWithNoSignedWrap(Other), RangeType);
+    Result = Result.intersectWith(sadd_sat(Other), RangeType);
+
   if (NoWrapKind & OBO::NoUnsignedWrap)
-    Result = Result.intersectWith(addWithNoUnsignedWrap(Other), RangeType);
+    Result = Result.intersectWith(uadd_sat(Other), RangeType);
+
   return Result;
 }
 
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