Changeset 276525 in webkit

Timestamp:

Apr 23, 2021, 3:46:21 PM (5 years ago)

Author:

Russell Epstein

Message:

Cherry-pick r276524. rdar://problem/77089783

Fix B3 strength reduction for shl.
​https://bugs.webkit.org/show_bug.cgi?id=224913
rdar://76978874

Reviewed by Michael Saboff.

If the operation can potentially either underflow or overflow, then the result
can be any value.

• b3/B3ReduceStrength.cpp:

git-svn-id: ​https://svn.webkit.org/repository/webkit/trunk@276524 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Location:

branches/safari-611-branch/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• b3/B3ReduceStrength.cpp (modified) (1 diff)

branches/safari-611-branch/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2021-04-23  Ruben Turcios  <rubent_22@apple.com>
+
+        Cherry-pick r276524. rdar://problem/77089783
+
+    Fix B3 strength reduction for shl.
+    https://bugs.webkit.org/show_bug.cgi?id=224913
+    rdar://76978874
+    
+    Reviewed by Michael Saboff.
+    
+    If the operation can potentially either underflow or overflow, then the result
+    can be any value.
+    
+    * b3/B3ReduceStrength.cpp:
+    
+    
+    
+    git-svn-id: https://svn.webkit.org/repository/webkit/trunk@276524 268f45cc-cd09-0410-ab3c-d52691b4dbfc
+
+    2021-04-23  Mark Lam  <mark.lam@apple.com>
+
+            Fix B3 strength reduction for shl.
+            https://bugs.webkit.org/show_bug.cgi?id=224913
+            rdar://76978874
+
+            Reviewed by Michael Saboff.
+
+            If the operation can potentially either underflow or overflow, then the result
+            can be any value.
+
+            * b3/B3ReduceStrength.cpp:
+
 2021-04-23  Russell Epstein  <repstein@apple.com>
 

branches/safari-611-branch/Source/JavaScriptCore/b3/B3ReduceStrength.cpp

@@ -241 +241 @@
         T newMax = static_cast<T>(m_max) << static_cast<T>(shiftAmount);
 
-        if ((newMin >> shiftAmount) != static_cast<T>(m_min))
+        if (((newMin >> shiftAmount) != static_cast<T>(m_min))
+            || ((newMax >> shiftAmount) != static_cast<T>(m_max))) {
             newMin = std::numeric_limits<T>::min();
-        if ((newMax >> shiftAmount) != static_cast<T>(m_max))
             newMax = std::numeric_limits<T>::max();
+        }
 
         return IntRange(newMin, newMax);