MIPS: Fix improper use of odd FP reg on mips32r6

src/mips/assembler-mips.h

 // 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 50 matching lines @@
   V(f0)  V(f1)  V(f2)  V(f3)  V(f4)  V(f5)  V(f6)  V(f7)  \
   V(f8)  V(f9)  V(f10) V(f11) V(f12) V(f13) V(f14) V(f15) \
   V(f16) V(f17) V(f18) V(f19) V(f20) V(f21) V(f22) V(f23) \
   V(f24) V(f25) V(f26) V(f27) V(f28) V(f29) V(f30) V(f31)
 
 #define FLOAT_REGISTERS DOUBLE_REGISTERS
 #define SIMD128_REGISTERS DOUBLE_REGISTERS
 
 #define ALLOCATABLE_DOUBLE_REGISTERS(V)                   \
   V(f0)  V(f2)  V(f4)  V(f6)  V(f8)  V(f10) V(f12) V(f14) \
-  V(f16) V(f18) V(f20) V(f22) V(f24) V(f26)
+  V(f16) V(f18) V(f20) V(f22) V(f24)
 // clang-format on
 
 // CPU Registers.
 //
 // 1) We would prefer to use an enum, but enum values are assignment-
 // compatible with int, which has caused code-generation bugs.
 //
 // 2) We would prefer to use a class instead of a struct but we don't like
 // the register initialization to depend on the particular initialization
 // order (which appears to be different on OS X, Linux, and Windows for the
@@ skipping 193 matching lines @@
 // Defined using #define instead of "static const Register&" because Clang
 // complains otherwise when a compilation unit that includes this header
 // doesn't use the variables.
 #define kRootRegister s6
 #define cp s7
 #define kLithiumScratchReg s3
 #define kLithiumScratchReg2 s4
 #define kLithiumScratchDouble f30
 #define kDoubleRegZero f28
 // Used on mips32r6 for compare operations.
-// We use the last non-callee saved odd register for O32 ABI
-#define kDoubleCompareReg f19
+#define kDoubleCompareReg f26
 
 // FPU (coprocessor 1) control registers.
 // Currently only FCSR (#31) is implemented.
 struct FPUControlRegister {
   bool is_valid() const { return reg_code == kFCSRRegister; }
   bool is(FPUControlRegister creg) const { return reg_code == creg.reg_code; }
   int code() const {
     DCHECK(is_valid());
     return reg_code;
   }
@@ skipping 1179 matching lines @@
  public:
   explicit EnsureSpace(Assembler* assembler) {
     assembler->CheckBuffer();
   }
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ARM_ASSEMBLER_MIPS_H_