Bug 1278283 - Introduce popcnt abstraction for ARM. r=nbp

--HG--
extra : rebase_source : 190e685184a2fbd93fc0fe82ff4322f286bc13e6

js/src/jit/MacroAssembler.h

@@ -873,8 +873,11 @@ class MacroAssembler : public MacroAssemblerSpecific
     inline void clz64(Register64 src, Register64 dest) DEFINED_ON(x64);
     inline void ctz64(Register64 src, Register64 dest) DEFINED_ON(x64);
 
+    // On x86_shared, temp may be Invalid only if the chip has the POPCNT instruction.
+    // On ARM, temp may never be Invalid.
+    inline void popcnt32(Register src, Register dest, Register temp) DEFINED_ON(arm, x86_shared);
+
     // temp may be invalid only if the chip has the POPCNT instruction.
-    inline void popcnt32(Register src, Register dest, Register temp) DEFINED_ON(x86_shared);
     inline void popcnt64(Register64 src, Register64 dest, Register64 temp) DEFINED_ON(x64);
 
     // ===============================================================

js/src/jit/arm/CodeGenerator-arm.cpp

@@ -925,22 +925,9 @@ CodeGeneratorARM::visitPopcntI(LPopcntI* ins)
     Register input = ToRegister(ins->input());
     Register output = ToRegister(ins->output());
 
-    // Equivalent to GCC output of mozilla::CountPopulation32()
     Register tmp = ToRegister(ins->temp());
 
-    masm.ma_mov(input, output);
-    masm.as_mov(tmp, asr(output, 1));
-    masm.ma_and(Imm32(0x55555555), tmp);
-    masm.ma_sub(output, tmp, output);
-    masm.as_mov(tmp, asr(output, 2));
-    masm.ma_and(Imm32(0x33333333), output);
-    masm.ma_and(Imm32(0x33333333), tmp);
-    masm.ma_add(output, tmp, output);
-    masm.as_add(output, output, lsr(output, 4));
-    masm.ma_and(Imm32(0xF0F0F0F), output);
-    masm.as_add(output, output, lsl(output, 8));
-    masm.as_add(output, output, lsl(output, 16));
-    masm.as_mov(output, asr(output, 24));
+    masm.popcnt32(input, output, tmp);
 }
 
 void

js/src/jit/arm/MacroAssembler-arm-inl.h

@@ -628,6 +628,27 @@ MacroAssembler::ctz32(Register src, Register dest, bool knownNotZero)
     ma_ctz(src, dest);
 }
 
+void
+MacroAssembler::popcnt32(Register input,  Register output, Register tmp)
+{
+    // Equivalent to GCC output of mozilla::CountPopulation32()
+
+    if (input != output)
+        ma_mov(input, output);
+    as_mov(tmp, asr(output, 1));
+    ma_and(Imm32(0x55555555), tmp);
+    ma_sub(output, tmp, output);
+    as_mov(tmp, asr(output, 2));
+    ma_and(Imm32(0x33333333), output);
+    ma_and(Imm32(0x33333333), tmp);
+    ma_add(output, tmp, output);
+    as_add(output, output, lsr(output, 4));
+    ma_and(Imm32(0xF0F0F0F), output);
+    as_add(output, output, lsl(output, 8));
+    as_add(output, output, lsl(output, 16));
+    as_mov(output, asr(output, 24));
+}
+
 // ===============================================================
 // Branch functions