Add a new isSignWrappedSet() method to ConstantRange.

Fix zeroExtend and signExtend to support empty sets, and to return the smallest
possible result set which contains the extension of each element in their
inputs. For example zext i8 [100, 10) to i16 is now [0, 256), not i16 [100, 10)
which contains 63446 members.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113187 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 42 insertions, 7 deletions

diff --git a/include/llvm/Support/ConstantRange.h b/include/llvm/Support/ConstantRange.h
index 29086b2..2af2cf6 100644
--- a/include/llvm/Support/ConstantRange.h
+++ b/include/llvm/Support/ConstantRange.h
@@ -92,6 +92,11 @@ public:
   ///
   bool isWrappedSet() const;
 
+  /// isSignWrappedSet - Return true if this set wraps around the INT_MIN of
+  /// its bitwidth, for example: i8 [120, 140).
+  ///
+  bool isSignWrappedSet() const;
+
   /// contains - Return true if the specified value is in the set.
   ///
   bool contains(const APInt &Val) const;
diff --git a/lib/Support/ConstantRange.cpp b/lib/Support/ConstantRange.cpp
index 8ef3785..defb818 100644
--- a/lib/Support/ConstantRange.cpp
+++ b/lib/Support/ConstantRange.cpp
@@ -115,6 +115,14 @@ bool ConstantRange::isWrappedSet() const {
   return Lower.ugt(Upper);
 }
 
+/// isSignWrappedSet - Return true if this set wraps around the INT_MIN of
+/// its bitwidth, for example: i8 [120, 140).
+///
+bool ConstantRange::isSignWrappedSet() const {
+  return contains(APInt::getSignedMaxValue(getBitWidth())) &&
+         contains(APInt::getSignedMinValue(getBitWidth()));
+}
+
 /// getSetSize - Return the number of elements in this set.
 ///
 APInt ConstantRange::getSetSize() const {
@@ -408,10 +416,12 @@ ConstantRange ConstantRange::unionWith(const ConstantRange &CR) const {
 /// correspond to the possible range of values as if the source range had been
 /// zero extended.
 ConstantRange ConstantRange::zeroExtend(uint32_t DstTySize) const {
+  if (isEmptySet()) return ConstantRange(DstTySize, /*isFullSet=*/false);
+
   unsigned SrcTySize = getBitWidth();
   assert(SrcTySize < DstTySize && "Not a value extension");
-  if (isFullSet())
-    // Change a source full set into [0, 1 << 8*numbytes)
+  if (isFullSet() || isWrappedSet())
+    // Change into [0, 1 << src bit width)
     return ConstantRange(APInt(DstTySize,0), APInt(DstTySize,1).shl(SrcTySize));
 
   APInt L = Lower; L.zext(DstTySize);
@@ -424,9 +434,11 @@ ConstantRange ConstantRange::zeroExtend(uint32_t DstTySize) const {
 /// correspond to the possible range of values as if the source range had been
 /// sign extended.
 ConstantRange ConstantRange::signExtend(uint32_t DstTySize) const {
+  if (isEmptySet()) return ConstantRange(DstTySize, /*isFullSet=*/false);
+
   unsigned SrcTySize = getBitWidth();
   assert(SrcTySize < DstTySize && "Not a value extension");
-  if (isFullSet()) {
+  if (isFullSet() || isSignWrappedSet()) {
     return ConstantRange(APInt::getHighBitsSet(DstTySize,DstTySize-SrcTySize+1),
                          APInt::getLowBitsSet(DstTySize, SrcTySize-1) + 1);
   }
diff --git a/unittests/Support/ConstantRangeTest.cpp b/unittests/Support/ConstantRangeTest.cpp
index 091ecd4..1cedeae 100644
--- a/unittests/Support/ConstantRangeTest.cpp
+++ b/unittests/Support/ConstantRangeTest.cpp
@@ -146,6 +146,22 @@ TEST_F(ConstantRangeTest, GetMinsAndMaxes) {
             APInt(4, 7));
 }
 
+TEST_F(ConstantRangeTest, SignWrapped) {
+  EXPECT_TRUE(Full.isSignWrappedSet());
+  EXPECT_FALSE(Empty.isSignWrappedSet());
+  EXPECT_FALSE(One.isSignWrappedSet());
+  EXPECT_FALSE(Some.isSignWrappedSet());
+  EXPECT_TRUE(Wrap.isSignWrappedSet());
+
+  EXPECT_FALSE(ConstantRange(APInt(8, 127), APInt(8, 128)).isSignWrappedSet());
+  EXPECT_TRUE(ConstantRange(APInt(8, 127), APInt(8, 129)).isSignWrappedSet());
+  EXPECT_FALSE(ConstantRange(APInt(8, 128), APInt(8, 129)).isSignWrappedSet());
+  EXPECT_TRUE(ConstantRange(APInt(8, 10), APInt(8, 9)).isSignWrappedSet());
+  EXPECT_TRUE(ConstantRange(APInt(8, 10), APInt(8, 250)).isSignWrappedSet());
+  EXPECT_FALSE(ConstantRange(APInt(8, 250), APInt(8, 10)).isSignWrappedSet());
+  EXPECT_FALSE(ConstantRange(APInt(8, 250), APInt(8, 251)).isSignWrappedSet());
+}
+
 TEST_F(ConstantRangeTest, Trunc) {
   ConstantRange TFull = Full.truncate(10);
   ConstantRange TEmpty = Empty.truncate(10);
@@ -171,8 +187,7 @@ TEST_F(ConstantRangeTest, ZExt) {
                                 APInt(One.getUpper()).zext(20)));
   EXPECT_EQ(ZSome, ConstantRange(APInt(Some.getLower()).zext(20),
                                  APInt(Some.getUpper()).zext(20)));
-  EXPECT_EQ(ZWrap, ConstantRange(APInt(Wrap.getLower()).zext(20),
-                                 APInt(Wrap.getUpper()).zext(20)));
+  EXPECT_EQ(ZWrap, ConstantRange(APInt(20, 0), APInt(20, 0x10000)));
 }
 
 TEST_F(ConstantRangeTest, SExt) {
@@ -188,8 +203,11 @@ TEST_F(ConstantRangeTest, SExt) {
                                 APInt(One.getUpper()).sext(20)));
   EXPECT_EQ(SSome, ConstantRange(APInt(Some.getLower()).sext(20),
                                  APInt(Some.getUpper()).sext(20)));
-  EXPECT_EQ(SWrap, ConstantRange(APInt(Wrap.getLower()).sext(20),
-                                 APInt(Wrap.getUpper()).sext(20)));
+  EXPECT_EQ(SWrap, ConstantRange(APInt(20, (uint64_t)INT16_MIN, true),
+                                 APInt(20, INT16_MAX + 1, true)));
+
+  EXPECT_EQ(ConstantRange(APInt(8, 120), APInt(8, 140)).signExtend(16),
+            ConstantRange(APInt(16, -128), APInt(16, 128)));
 }
 
 TEST_F(ConstantRangeTest, IntersectWith) {