Faster implementation of Math.exp()

src/ia32/code-stubs-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3097 matching lines @@
     // B ^ E = (2^(E * log2(B)) - 1) + 1 = (2^X - 1) + 1 for X = E * log2(B)
     // FYL2X calculates st(1) * log2(st(0))
     __ fyl2x();    // X
     __ fld(0);     // X, X
     __ frndint();  // rnd(X), X
     __ fsub(1);    // rnd(X), X-rnd(X)
     __ fxch(1);    // X - rnd(X), rnd(X)
     // F2XM1 calculates 2^st(0) - 1 for -1 < st(0) < 1
     __ f2xm1();    // 2^(X-rnd(X)) - 1, rnd(X)
     __ fld1();     // 1, 2^(X-rnd(X)) - 1, rnd(X)
-    __ faddp(1);   // 1, 2^(X-rnd(X)), rnd(X)
+    __ faddp(1);   // 2^(X-rnd(X)), rnd(X)
     // FSCALE calculates st(0) * 2^st(1)
     __ fscale();   // 2^X, rnd(X)
-    __ fstp(1);
+    __ fstp(1);    // 2^X
     // Bail out to runtime in case of exceptions in the status word.
     __ fnstsw_ax();
     __ test_b(eax, 0x5F);  // We check for all but precision exception.
     __ j(not_zero, &fast_power_failed, Label::kNear);
     __ fstp_d(Operand(esp, 0));
     __ movdbl(double_result, Operand(esp, 0));
     __ add(esp, Immediate(kDoubleSize));
     __ jmp(&done);
 
     __ bind(&fast_power_failed);
@@ skipping 4317 matching lines @@
   // Restore ecx.
   __ pop(ecx);
   __ ret(0);
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32