Revision: 4477
Author: [email protected]
Date: Thu Apr 22 10:25:42 2010
Log: Speed up random on ARM. Patch committed for
[email protected]. See http://codereview.chromium.org/1689007
http://code.google.com/p/v8/source/detail?r=4477
Modified:
/branches/bleeding_edge/src/arm/codegen-arm.cc
=======================================
--- /branches/bleeding_edge/src/arm/codegen-arm.cc Thu Apr 22 05:20:36 2010
+++ /branches/bleeding_edge/src/arm/codegen-arm.cc Thu Apr 22 10:25:42 2010
@@ -4232,19 +4232,49 @@
Label slow_allocate_heapnumber;
Label heapnumber_allocated;
- __ AllocateHeapNumber(r0, r1, r2, &slow_allocate_heapnumber);
+ __ AllocateHeapNumber(r4, r1, r2, &slow_allocate_heapnumber);
__ jmp(&heapnumber_allocated);
__ bind(&slow_allocate_heapnumber);
+ // To allocate a heap number, and ensure that it is not a smi, we
+ // call the runtime function FUnaryMinus on 0, returning the double
+ // -0.0. A new, distinct heap number is returned each time.
__ mov(r0, Operand(Smi::FromInt(0)));
__ push(r0);
__ CallRuntime(Runtime::kNumberUnaryMinus, 1);
+ __ mov(r4, Operand(r0));
__ bind(&heapnumber_allocated);
- __ PrepareCallCFunction(1, r1);
- __ CallCFunction(
- ExternalReference::fill_heap_number_with_random_function(), 1);
- frame_->EmitPush(r0);
+
+ // Convert 32 random bits in r0 to 0.(32 random bits) in a double
+ // by computing:
+ // ( 1.(20 0s)(32 random bits) x 2^20 ) - (1.0 x 2^20)).
+ if (CpuFeatures::IsSupported(VFP3)) {
+ __ PrepareCallCFunction(0, r1);
+ __ CallCFunction(ExternalReference::random_uint32_function(), 0);
+
+ CpuFeatures::Scope scope(VFP3);
+ // 0x41300000 is the top half of 1.0 x 2^20 as a double.
+ // Create this constant using mov/orr to avoid PC relative load.
+ __ mov(r1, Operand(0x41000000));
+ __ orr(r1, r1, Operand(0x300000));
+ // Move 0x41300000xxxxxxxx (x = random bits) to VFP.
+ __ vmov(d7, r0, r1);
+ // Move 0x4130000000000000 to VFP.
+ __ mov(r0, Operand(0));
+ __ vmov(d8, r0, r1);
+ // Subtract and store the result in the heap number.
+ __ vsub(d7, d7, d8);
+ __ sub(r0, r4, Operand(kHeapObjectTag));
+ __ vstr(d7, r0, HeapNumber::kValueOffset);
+ frame_->EmitPush(r4);
+ } else {
+ __ mov(r0, Operand(r4));
+ __ PrepareCallCFunction(1, r1);
+ __ CallCFunction(
+ ExternalReference::fill_heap_number_with_random_function(), 1);
+ frame_->EmitPush(r0);
+ }
}
--
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