[Turbofan] Add concept of FP register aliasing on ARM 32.

test/cctest/compiler/test-run-native-calls.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/assembler.h"
 #include "src/codegen.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/raw-machine-assembler.h"
 #include "src/machine-type.h"
 #include "src/register-configuration.h"
@@ skipping 69 matching lines @@
   RegisterPairs()
       : Pairs(100, GetRegConfig()->num_allocatable_general_registers(),
               GetRegConfig()->allocatable_general_codes()) {}
 };
 
 
 // Pairs of double registers.
 class Float32RegisterPairs : public Pairs {
  public:
   Float32RegisterPairs()
-      : Pairs(100, GetRegConfig()->num_allocatable_aliased_double_registers(),
-              GetRegConfig()->allocatable_double_codes()) {}
+      : Pairs(
+            100,
+#if V8_TARGET_ARCH_ARM
+            // TODO(bbudge) Modify wasm linkage to allow use of all float regs.
+            GetRegConfig()->num_allocatable_double_registers() / 2 - 2,
+#else
+            GetRegConfig()->num_allocatable_double_registers(),
+#endif
+            GetRegConfig()->allocatable_double_codes()) {
+  }
 };
 
 
 // Pairs of double registers.
 class Float64RegisterPairs : public Pairs {
  public:
   Float64RegisterPairs()
       : Pairs(100, GetRegConfig()->num_allocatable_double_registers(),
               GetRegConfig()->allocatable_double_codes()) {}
 };
@@ skipping 18 matching lines @@
   int fp_offset;
   int* fp_regs;
 
   int stack_offset;
 
   LinkageLocation Next(MachineType type) {
     if (IsFloatingPoint(type.representation())) {
       // Allocate a floating point register/stack location.
       if (fp_offset < fp_count) {
         int code = fp_regs[fp_offset++];
+#if V8_TARGET_ARCH_ARM
+        // TODO(bbudge) Modify wasm linkage to allow use of all float regs.
+        if (type.representation() == MachineRepresentation::kFloat32) code *= 2;
+#endif
         return LinkageLocation::ForRegister(code, type);
       } else {
         int offset = -1 - stack_offset;
         stack_offset += StackWords(type);
         return LinkageLocation::ForCallerFrameSlot(offset, type);
       }
     } else {
       // Allocate a general purpose register/stack location.
       if (gp_offset < gp_count) {
         return LinkageLocation::ForRegister(gp_regs[gp_offset++], type);
@@ skipping 1052 matching lines @@
   TestStackSlot(MachineType::Float32(), magic);
 }
 
 TEST(RunStackSlotFloat64) {
   double magic = 3456.375;
   TestStackSlot(MachineType::Float64(), magic);
 }
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8