Consider expression "0.0 - X" as the negation of X if

  - this expression is explicitly marked no-signed-zero, or
  - no-signed-zero of this expression can be derived from some context.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171922 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 0 deletions

diff --git a/lib/IR/Constants.cpp b/lib/IR/Constants.cpp
index 4b58599955..812692f3fa 100644
--- a/lib/IR/Constants.cpp
+++ b/lib/IR/Constants.cpp
@@ -51,6 +51,15 @@ bool Constant::isNegativeZeroValue() const {
   return isNullValue();
 }
 
+bool Constant::isZeroValue() const {
+  // Floating point values have an explicit -0.0 value.
+  if (const ConstantFP *CFP = dyn_cast<ConstantFP>(this))
+    return CFP->isZero();
+
+  // Otherwise, just use +0.0.
+  return isNullValue();
+}
+
 bool Constant::isNullValue() const {
   // 0 is null.
   if (const ConstantInt *CI = dyn_cast<ConstantInt>(this))