Support inlining and crankshaft optimization of Math.random.

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index bafe74eec5e52c2c9bc3566963e354da497dd531..58dca6989a5a2da973efed7a1401230a6dbeebec 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -2926,6 +2926,41 @@ void LCodeGen::DoPower(LPower* instr) {
 }
 
 
+void LCodeGen::DoRandom(LRandom* instr) {
+  // Having marked this instruction as a call we can use any
+  // registers.
+  ASSERT(ToDoubleRegister(instr->result()).is(xmm1));
+
+  // Choose the right register for the first argument depending on
+  // calling convention.
+#ifdef _WIN64
+  ASSERT(ToRegister(instr->InputAt(0)).is(rcx));
+  Register global_object = rdx;

[Jakob Kummerow, 2012/01/11 08:10:40]

Unused variable. Also, s/rdx/rcx/.

[Mads Ager (chromium), 2012/01/11 10:24:46]

Done.

+#else
+  ASSERT(ToRegister(instr->InputAt(0)).is(rdi));
+  Register global_object = rdi;
+#endif
+
+  __ PrepareCallCFunction(1);
+#ifdef _WIN64

[Jakob Kummerow, 2012/01/11 08:10:40]

If you made use of the |global_object| variable defined above, you wouldn't need
this #ifdef.

[Mads Ager (chromium), 2012/01/11 10:24:46]

Whoops. Thanks Jakob, that was indeed the intention.

+  __ movq(rcx, FieldOperand(rcx, GlobalObject::kGlobalContextOffset));
+#else
+  __ movq(rdi, FieldOperand(rdi, GlobalObject::kGlobalContextOffset));
+#endif
+  __ CallCFunction(ExternalReference::random_uint32_function(isolate()), 1);
+
+  // Convert 32 random bits in rax to 0.(32 random bits) in a double
+  // by computing:
+  // ( 1.(20 0s)(32 random bits) x 2^20 ) - (1.0 x 2^20)).
+  __ movl(rcx, Immediate(0x49800000));  // 1.0 x 2^20 as single.
+  __ movd(xmm2, rcx);
+  __ movd(xmm1, rax);
+  __ cvtss2sd(xmm2, xmm2);
+  __ xorps(xmm1, xmm2);
+  __ subsd(xmm1, xmm2);
+}
+
+
 void LCodeGen::DoMathLog(LUnaryMathOperation* instr) {
   ASSERT(ToDoubleRegister(instr->result()).is(xmm1));
   TranscendentalCacheStub stub(TranscendentalCache::LOG,