commit 7e733eab2f11fceb24d6b4f25c27d7ba7d92d97e
author Nuno Lopes <nunoplopes@sapo.pt> Mon Jul 16 20:47:16 2012 +0000
committer Nuno Lopes <nunoplopes@sapo.pt> Mon Jul 16 20:47:16 2012 +0000
tree ab82e7cc0758a49e83f62f6991993c738edcf2a6
parent 98819c9d1e3b929e9ebab0e8cd3edb31aad21bd8

teach ConstantRange that zero times X is always zero

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160317 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/ConstantRange.cpp

diff --git a/lib/Support/ConstantRange.cpp b/lib/Support/ConstantRange.cpp
index b83dccc..221ca94 100644
--- a/lib/Support/ConstantRange.cpp
+++ b/lib/Support/ConstantRange.cpp
@@ -537,6 +537,12 @@
 
   if (isEmptySet() || Other.isEmptySet())
     return ConstantRange(getBitWidth(), /*isFullSet=*/false);
+
+  // If any of the operands is zero, then the result is also zero.
+  if ((getSingleElement() && *getSingleElement() == 0) ||
+      (Other.getSingleElement() && *Other.getSingleElement() == 0))
+    return ConstantRange(APInt(getBitWidth(), 0));
+
   if (isFullSet() || Other.isFullSet())
     return ConstantRange(getBitWidth(), /*isFullSet=*/true);
 

unittests/Support/ConstantRangeTest.cpp

diff --git a/unittests/Support/ConstantRangeTest.cpp b/unittests/Support/ConstantRangeTest.cpp
index 6d2510c..7d4055f 100644
--- a/unittests/Support/ConstantRangeTest.cpp
+++ b/unittests/Support/ConstantRangeTest.cpp
@@ -382,6 +382,14 @@
   EXPECT_EQ(Some.multiply(Wrap), Full);
   EXPECT_EQ(Wrap.multiply(Wrap), Full);
 
+  ConstantRange Zero(APInt(16, 0));
+  EXPECT_EQ(Zero.multiply(Full), Zero);
+  EXPECT_EQ(Zero.multiply(Some), Zero);
+  EXPECT_EQ(Zero.multiply(Wrap), Zero);
+  EXPECT_EQ(Full.multiply(Zero), Zero);
+  EXPECT_EQ(Some.multiply(Zero), Zero);
+  EXPECT_EQ(Wrap.multiply(Zero), Zero);
+
   // http://llvm.org/PR4545
   EXPECT_EQ(ConstantRange(APInt(4, 1), APInt(4, 6)).multiply(
                 ConstantRange(APInt(4, 6), APInt(4, 2))),