[PATCH] [ConstantRange] Add a smultiply method for signed multiply

[James Molloy]

Hi hfinkel,

multiply() treats its limits as unsigned values - add an equivalent for signed values.

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D7789

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

Index: include/llvm/IR/ConstantRange.h
===================================================================
--- include/llvm/IR/ConstantRange.h
+++ include/llvm/IR/ConstantRange.h
@@ -208,11 +208,18 @@
   ConstantRange sub(const ConstantRange &Other) const;
 
   /// Return a new range representing the possible values resulting
-  /// from a multiplication of a value in this range and a value in \p Other.
+  /// from a multiplication of a value in this range and a value in \p Other,
+  /// treating both this and \p Other as unsigned ranges.
   /// TODO: This isn't fully implemented yet.
   ConstantRange multiply(const ConstantRange &Other) const;
 
   /// Return a new range representing the possible values resulting
+  /// from a multiplication of a value in this range and a value in \p Other,
+  /// treating both this and \p Other as signed ranges.
+  /// TODO: This isn't fully implemented yet.
+  ConstantRange smultiply(const ConstantRange &Other) const;
+
+  /// Return a new range representing the possible values resulting
   /// from a signed maximum of a value in this range and a value in \p Other.
   ConstantRange smax(const ConstantRange &Other) const;
 
Index: lib/IR/ConstantRange.cpp
===================================================================
--- lib/IR/ConstantRange.cpp
+++ lib/IR/ConstantRange.cpp
@@ -598,6 +598,26 @@
 }
 
 ConstantRange
+ConstantRange::smultiply(const ConstantRange &Other) const {
+  // TODO: If either operand is a single element and the multiply is known to
+  // be non-wrapping, round the result min and max value to the appropriate
+  // multiple of that element. If wrapping is possible, at least adjust the
+  // range according to the greatest power-of-two factor of the single element.
+
+  if (isEmptySet() || Other.isEmptySet())
+    return ConstantRange(getBitWidth(), /*isFullSet=*/false);
+
+  APInt this_min = getSignedMin().sext(getBitWidth() * 2);
+  APInt this_max = getSignedMax().sext(getBitWidth() * 2);
+  APInt Other_min = Other.getSignedMin().sext(getBitWidth() * 2);
+  APInt Other_max = Other.getSignedMax().sext(getBitWidth() * 2);
+
+  ConstantRange Result_zext = ConstantRange(this_min * Other_min,
+                                            this_max * Other_max + 1);
+  return Result_zext.truncate(getBitWidth());
+}
+
+ConstantRange
 ConstantRange::smax(const ConstantRange &Other) const {
   // X smax Y is: range(smax(X_smin, Y_smin),
   //                    smax(X_smax, Y_smax))

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