Changeset 240650 in webkit for trunk/Source/JavaScriptCore

Timestamp:

Jan 29, 2019, 2:41:27 AM (6 years ago)

Author:

[email protected]

Message:

[ARM] Check for negative zero instead of just zero
​https://bugs.webkit.org/show_bug.cgi?id=193689

Reviewed by Mark Lam.

ARM now performs a negative zero check in branchConvertDoubleToInt32 instead
of just bailing out for zero.

• assembler/MacroAssemblerARMv7.h:

(JSC::MacroAssemblerARMv7::branchConvertDoubleToInt32):

Location:

trunk/Source/JavaScriptCore

Files:

• ChangeLog (modified) (1 diff)
• assembler/ARMv7Assembler.h (modified) (1 diff)
• assembler/MacroAssemblerARMv7.h (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2019-01-29  Dominik Infuehr  <[email protected]>
+
+        [ARM] Check for negative zero instead of just zero
+        https://bugs.webkit.org/show_bug.cgi?id=193689
+
+        Reviewed by Mark Lam.
+
+        ARM now performs a negative zero check in branchConvertDoubleToInt32 instead
+        of just bailing out for zero.
+
+        * assembler/MacroAssemblerARMv7.h:
+        (JSC::MacroAssemblerARMv7::branchConvertDoubleToInt32):
+
 2019-01-28  Devin Rousso  <[email protected]>
 

trunk/Source/JavaScriptCore/assembler/ARMv7Assembler.h

@@ -171 +171 @@
         ASSERT(reg < d16);
         return (FPSingleRegisterID)(reg << 1);
+    }
+
+    inline FPSingleRegisterID asSingleUpper(FPDoubleRegisterID reg)
+    {
+        ASSERT(reg < d16);
+        return (FPSingleRegisterID)((reg << 1) + 1);
     }
 

trunk/Source/JavaScriptCore/assembler/MacroAssemblerARMv7.h

@@ -1253 +1253 @@
         failureCases.append(branchDouble(DoubleNotEqualOrUnordered, src, fpTempRegister));
 
-        // If the result is zero, it might have been -0.0, and the double comparison won't catch this!
-        if (negZeroCheck)
-            failureCases.append(branchTest32(Zero, dest));
+        // Test for negative zero.
+        if (negZeroCheck) {
+            Jump valueIsNonZero = branchTest32(NonZero, dest);
+            m_assembler.vmov(dataTempRegister, ARMRegisters::asSingleUpper(src));
+            failureCases.append(branch32(LessThan, dataTempRegister, TrustedImm32(0)));
+            valueIsNonZero.link(this);
+        }
     }