Reland of [turbofan] ARM: Implement vswp and use in gap resolver

src/arm/assembler-arm.cc

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // 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.
 //
@@ skipping 3887 matching lines @@
   // 000(18-16) | Vd(15-12) | 101000(11-6) | M(5) | 1(4) | Vm(3-0)
   DCHECK(CpuFeatures::IsSupported(NEON));
   int vd, d;
   dst.split_code(&vd, &d);
   int vm, m;
   src.split_code(&vm, &m);
   emit(0xFU*B28 | B25 | (dt & NeonDataTypeUMask) | B23 | d*B22 |
         (dt & NeonDataTypeSizeMask)*B19 | vd*B12 | 0xA*B8 | m*B5 | B4 | vm);
 }
 
+void Assembler::vswp(DwVfpRegister srcdst0, DwVfpRegister srcdst1) {
+  DCHECK(!srcdst0.is(kScratchDoubleReg));
+  DCHECK(!srcdst1.is(kScratchDoubleReg));
+
+  if (srcdst0.is(srcdst1)) return;  // Swapping aliased registers emits nothing.
+
+  if (CpuFeatures::IsSupported(NEON)) {
+    // Instruction details available in ARM DDI 0406C.b, A8.8.418.
+    // 1111(31-28) | 00111(27-23) | D(22) | 110010(21-16) |
+    // Vd(15-12) | 000000(11-6) | M(5) | 0(4) | Vm(3-0)
+    int vd, d;
+    srcdst0.split_code(&vd, &d);
+    int vm, m;
+    srcdst1.split_code(&vm, &m);
+    emit(0xFU * B28 | 7 * B23 | d * B22 | 0x32 * B16 | vd * B12 | m * B5 | vm);
+  } else {
+    vmov(kScratchDoubleReg, srcdst0);
+    vmov(srcdst0, srcdst1);
+    vmov(srcdst1, kScratchDoubleReg);
+  }
+}
 
 // Pseudo instructions.
 void Assembler::nop(int type) {
   // ARMv6{K/T2} and v7 have an actual NOP instruction but it serializes
   // some of the CPU's pipeline and has to issue. Older ARM chips simply used
   // MOV Rx, Rx as NOP and it performs better even in newer CPUs.
   // We therefore use MOV Rx, Rx, even on newer CPUs, and use Rx to encode
   // a type.
   DCHECK(0 <= type && type <= 14);  // mov pc, pc isn't a nop.
   emit(al | 13*B21 | type*B12 | type);
@@ skipping 533 matching lines @@
     DCHECK(is_uint12(offset));
     instr_at_put(pc, SetLdrRegisterImmediateOffset(instr, offset));
   }
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM