[PATCH] D60574: [ConstantRange] Add unsignedMulMayOverflow()

[Nikita Popov via Phabricator via llvm-commits]

nikic created this revision.
nikic added a reviewer: lebedev.ri.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

Same as as other overflow checking methods, but for unsigned mul... in this case there is no cheap overflow criterion, so using umul_ov for the implementation.


Repository:
  rL LLVM

https://reviews.llvm.org/D60574

Files:
  llvm/include/llvm/IR/ConstantRange.h
  llvm/lib/IR/ConstantRange.cpp
  llvm/unittests/IR/ConstantRangeTest.cpp


Index: llvm/unittests/IR/ConstantRangeTest.cpp
===================================================================
--- llvm/unittests/IR/ConstantRangeTest.cpp
+++ llvm/unittests/IR/ConstantRangeTest.cpp
@@ -1578,6 +1578,18 @@
       });
 }
 
+TEST_F(ConstantRangeTest, UnsignedMulOverflowExhautive) {
+  TestOverflowExhaustive(
+      [](const APInt &N1, const APInt &N2) {
+        bool Overflow;
+        (void) N1.umul_ov(N2, Overflow);
+        return Overflow;
+      },
+      [](const ConstantRange &CR1, const ConstantRange &CR2) {
+        return CR1.unsignedMulMayOverflow(CR2);
+      });
+}
+
 TEST_F(ConstantRangeTest, SignedAddOverflowExhautive) {
   TestOverflowExhaustive(
       [](const APInt &N1, const APInt &N2) {
Index: llvm/lib/IR/ConstantRange.cpp
===================================================================
--- llvm/lib/IR/ConstantRange.cpp
+++ llvm/lib/IR/ConstantRange.cpp
@@ -1252,6 +1252,26 @@
   return OverflowResult::NeverOverflows;
 }
 
+ConstantRange::OverflowResult ConstantRange::unsignedMulMayOverflow(
+    const ConstantRange &Other) const {
+  if (isEmptySet() || Other.isEmptySet())
+    return OverflowResult::MayOverflow;
+
+  APInt Min = getUnsignedMin(), Max = getUnsignedMax();
+  APInt OtherMin = Other.getUnsignedMin(), OtherMax = Other.getUnsignedMax();
+  bool Overflow;
+
+  (void) Min.umul_ov(OtherMin, Overflow);
+  if (Overflow)
+    return OverflowResult::AlwaysOverflows;
+
+  (void) Max.umul_ov(OtherMax, Overflow);
+  if (Overflow)
+    return OverflowResult::MayOverflow;
+
+  return OverflowResult::NeverOverflows;
+}
+
 void ConstantRange::print(raw_ostream &OS) const {
   if (isFullSet())
     OS << "full-set";
Index: llvm/include/llvm/IR/ConstantRange.h
===================================================================
--- llvm/include/llvm/IR/ConstantRange.h
+++ llvm/include/llvm/IR/ConstantRange.h
@@ -399,6 +399,9 @@
   /// Return whether signed sub of the two ranges always/never overflows.
   OverflowResult signedSubMayOverflow(const ConstantRange &Other) const;
 
+  /// Return whether unsigned mul of the two ranges always/never overflows.
+  OverflowResult unsignedMulMayOverflow(const ConstantRange &Other) const;
+
   /// Print out the bounds to a stream.
   void print(raw_ostream &OS) const;
 


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D60574.194730.patch
Type: text/x-patch
Size: 2284 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20190411/dfabf179/attachment.bin>