Changeset 156016 in webkit for trunk/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp

Timestamp:

Sep 17, 2013, 6:04:31 PM (12 years ago)

Author:

[email protected]

Message:

DFG should use the (x & 0x7fffffff) trick for doing overflow and neg-zero checks on negation in one go
​https://bugs.webkit.org/show_bug.cgi?id=121520

Reviewed by Oliver Hunt.

• dfg/DFGSpeculativeJIT.cpp:

(JSC::DFG::SpeculativeJIT::compileArithNegate):

• ftl/FTLLowerDFGToLLVM.cpp:

(JSC::FTL::LowerDFGToLLVM::compileArithNegate):

File:

• trunk/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp (modified) (2 diffs)

trunk/Source/JavaScriptCore/ftl/FTLLowerDFGToLLVM.cpp

@@ -1018 +1018 @@
             if (bytecodeCanTruncateInteger(m_node->arithNodeFlags()))
                 result = m_out.neg(value);
-            else {
+            else if (bytecodeCanIgnoreNegativeZero(m_node->arithNodeFlags())) {
                 // We don't have a negate-with-overflow intrinsic. Hopefully this
                 // does the trick, though.
@@ -1024 +1024 @@
                 speculate(Overflow, noValue(), 0, m_out.extractValue(overflowResult, 1));
                 result = m_out.extractValue(overflowResult, 0);
-                speculate(NegativeZero, noValue(), 0, m_out.isZero32(result));
+            } else {
+                speculate(Overflow, noValue(), 0, m_out.testIsZero32(value, m_out.constInt32(0x7fffffff)));
+                result = m_out.neg(value);
             }