ARM: Tweak Math.exp.

src/arm/codegen-arm.cc

Index: src/arm/codegen-arm.cc
diff --git a/src/arm/codegen-arm.cc b/src/arm/codegen-arm.cc
index 5b80d6facc5ea8e4a0b2fb6fcf985a83bdbc1cba..57e227d86949e5085bef9bc9fbc8e7b1aa123990 100644
--- a/src/arm/codegen-arm.cc
+++ b/src/arm/codegen-arm.cc
@@ -775,50 +775,63 @@ void MathExpGenerator::EmitMathExp(MacroAssembler* masm,
   ASSERT(!temp2.is(temp3));
   ASSERT(ExternalReference::math_exp_constants(0).address() != NULL);
 
-  Label done;
+  Label zero, infinity, done;
 
   __ mov(temp3, Operand(ExternalReference::math_exp_constants(0)));
 
   __ vldr(double_scratch1, ExpConstant(0, temp3));
-  __ vmov(result, kDoubleRegZero);
   __ VFPCompareAndSetFlags(double_scratch1, input);
-  __ b(ge, &done);
+  __ b(ge, &zero);
+
   __ vldr(double_scratch2, ExpConstant(1, temp3));
   __ VFPCompareAndSetFlags(input, double_scratch2);
-  __ vldr(result, ExpConstant(2, temp3));
-  __ b(ge, &done);
+  __ b(ge, &infinity);
+
   __ vldr(double_scratch1, ExpConstant(3, temp3));
   __ vldr(result, ExpConstant(4, temp3));
   __ vmul(double_scratch1, double_scratch1, input);
   __ vadd(double_scratch1, double_scratch1, result);
-  __ vmov(temp2, temp1, double_scratch1);
+  __ VmovLow(temp2, double_scratch1);
   __ vsub(double_scratch1, double_scratch1, result);
   __ vldr(result, ExpConstant(6, temp3));
   __ vldr(double_scratch2, ExpConstant(5, temp3));
   __ vmul(double_scratch1, double_scratch1, double_scratch2);
   __ vsub(double_scratch1, double_scratch1, input);
   __ vsub(result, result, double_scratch1);
-  __ vmul(input, double_scratch1, double_scratch1);
-  __ vmul(result, result, input);
-  __ mov(temp1, Operand(temp2, LSR, 11));
+  __ vmul(double_scratch2, double_scratch1, double_scratch1);
+  __ vmul(result, result, double_scratch2);
   __ vldr(double_scratch2, ExpConstant(7, temp3));
   __ vmul(result, result, double_scratch2);
   __ vsub(result, result, double_scratch1);
-  __ vldr(double_scratch2, ExpConstant(8, temp3));
+  // Mov 1 in double_scratch2 as math_exp_constants_array[8] == 1.

[ulan, 2013/09/24 08:44:39]

Can we assert this in code?

[Rodolph Perfetta, 2013/09/24 10:39:36]

Done.

+  __ vmov(double_scratch2, 1);
   __ vadd(result, result, double_scratch2);
-  __ movw(ip, 0x7ff);
-  __ and_(temp2, temp2, Operand(ip));
+  __ mov(temp1, Operand(temp2, LSR, 11));
+  __ Ubfx(temp2, temp2, 0, 11);
   __ add(temp1, temp1, Operand(0x3ff));
-  __ mov(temp1, Operand(temp1, LSL, 20));
 
   // Must not call ExpConstant() after overwriting temp3!
   __ mov(temp3, Operand(ExternalReference::math_exp_log_table()));
-  __ ldr(ip, MemOperand(temp3, temp2, LSL, 3));
-  __ add(temp3, temp3, Operand(kPointerSize));
-  __ ldr(temp2, MemOperand(temp3, temp2, LSL, 3));
-  __ orr(temp1, temp1, temp2);
-  __ vmov(input, ip, temp1);
-  __ vmul(result, result, input);
+  __ add(temp3, temp3, Operand(temp2, LSL, 3));
+  __ ldm(ia, temp3, temp2.bit() | temp3.bit());
+  // The first word is loaded is the lower number register.
+  if (temp2.code() < temp3.code()) {
+    __ orr(temp1, temp3, Operand(temp1, LSL, 20));
+    __ vmov(double_scratch1, temp2, temp1);
+  } else {
+    __ orr(temp1, temp2, Operand(temp1, LSL, 20));
+    __ vmov(double_scratch1, temp3, temp1);
+  }
+  __ vmul(result, result, double_scratch1);
+  __ b(&done);
+
+  __ bind(&zero);
+  __ vmov(result, kDoubleRegZero);
+  __ b(&done);
+
+  __ bind(&infinity);
+  __ vldr(result, ExpConstant(2, temp3));
+
   __ bind(&done);
 }