[turbofan] Allow 0.0 as immediate for floating-point comparison on arm/arm64.

src/compiler/arm64/code-generator-arm64.cc

Index: src/compiler/arm64/code-generator-arm64.cc
diff --git a/src/compiler/arm64/code-generator-arm64.cc b/src/compiler/arm64/code-generator-arm64.cc
index ecdf148cab5c6516d96231a1925ec56f675e322e..478fcfa0ba1680830b21b05c9af233c4b63e2251 100644
--- a/src/compiler/arm64/code-generator-arm64.cc
+++ b/src/compiler/arm64/code-generator-arm64.cc
@@ -624,7 +624,14 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       __ Tst(i.InputRegister32(0), i.InputOperand32(1));
       break;
     case kArm64Float64Cmp:
-      __ Fcmp(i.InputDoubleRegister(0), i.InputDoubleRegister(1));
+      if (instr->InputAt(1)->IsDoubleRegister()) {
+        __ Fcmp(i.InputDoubleRegister(0), i.InputDoubleRegister(1));
+      } else {
+        DCHECK(instr->InputAt(1)->IsImmediate());
+        // 0.0 is the only immediate supported by fcmp instructions.
+        DCHECK(i.InputDouble(1) == 0.0);
+        __ Fcmp(i.InputDoubleRegister(0), i.InputDouble(1));
+      }
       break;
     case kArm64Float64Add:
       __ Fadd(i.OutputDoubleRegister(), i.InputDoubleRegister(0),