Fix Math.pow implementation with MinGW-w64

https://bugs.webkit.org/show_bug.cgi?id=105087

Patch by Jonathan Liu <net147@gmail.com> on 2012-12-17
Reviewed by Simon Hausmann.

The MinGW-w64 runtime has different behaviour for pow()
compared to other C runtimes. This results in the following
test262 tests failing with the latest MinGW-w64 runtime:
- S15.8.2.13_A14
- S15.8.2.13_A16
- S15.8.2.13_A20
- S15.8.2.13_A22

Handle the special cases that are different with MinGW-w64.

* runtime/MathObject.cpp:
(JSC::mathPow):

Change-Id: Ifad1aa24ac36f2d452e9166a4298525793597da3
git-svn-id: http://svn.webkit.org/repository/webkit/trunk@137895 268f45cc-cd09-0410-ab3c-d52691b4dbfc
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/Source/JavaScriptCore/runtime/MathObject.cpp b/Source/JavaScriptCore/runtime/MathObject.cpp
index 7634487ad..f939b8dd4 100644
--- a/Source/JavaScriptCore/runtime/MathObject.cpp
+++ b/Source/JavaScriptCore/runtime/MathObject.cpp
@@ -232,6 +232,22 @@ static ALWAYS_INLINE double mathPow(double x, double y)
 
 ALWAYS_INLINE double mathPow(double x, double y)
 {
+#if COMPILER(MINGW64)
+    // MinGW-w64 has a custom implementation for pow.
+    // This handles certain special cases that are different.
+    if ((x == 0.0 || isinf(x)) && isfinite(y)) {
+        double f;
+        if (modf(y, &f) != 0.0)
+            return ((x == 0.0) ^ (y > 0.0)) ? std::numeric_limits<double>::infinity() : 0.0;
+    }
+
+    if (x == 2.0) {
+        int yInt = static_cast<int>(y);
+        if (y == yInt)
+            return ldexp(1.0, yInt);
+    }
+#endif
+
     return pow(x, y);
 }