[vm, dbc] Remove bad assert from DBC deoptimization.

DBC's "FPU registers" are in fact stack slots.

Bug: dart-lang#35395
Change-Id: I64f90f29b55f3f9bb0fec863e1a13c651f364ee7
Reviewed-on: https://dart-review.googlesource.com/c/87271
Reviewed-by: Aart Bik <[email protected]>
Commit-Queue: Ryan Macnak <[email protected]>

Author: rmacnak-google

runtime/vm/compiler/assembler/assembler_dbc.cc

@@ -75,6 +75,10 @@ const char* Assembler::RegisterName(Register reg) {
   return Thread::Current()->zone()->PrintToString("R%d", reg);
 }
 
+const char* Assembler::FpuRegisterName(FpuRegister reg) {
+  return Thread::Current()->zone()->PrintToString("F%d", reg);
+}
+
 static int32_t EncodeJump(int32_t relative_pc) {
   return SimulatorBytecode::kJump | (relative_pc << 8);
 }

runtime/vm/compiler/assembler/assembler_dbc.h

@@ -45,7 +45,7 @@ class Assembler : public AssemblerBase {
 
   static const char* RegisterName(Register reg);
 
-  static const char* FpuRegisterName(FpuRegister reg) { return "?"; }
+  static const char* FpuRegisterName(FpuRegister reg);
 
   static uword GetBreakInstructionFiller() { return SimulatorBytecode::kTrap; }
 

runtime/vm/deopt_instructions.h

@@ -97,9 +97,9 @@ class DeoptContext {
 
   double FpuRegisterValue(FpuRegister reg) const {
     ASSERT(FlowGraphCompiler::SupportsUnboxedDoubles());
+#if !defined(TARGET_ARCH_DBC)
     ASSERT(fpu_registers_ != NULL);
     ASSERT(reg >= 0);
-#if !defined(TARGET_ARCH_DBC)
     ASSERT(reg < kNumberOfFpuRegisters);
     return *reinterpret_cast<double*>(&fpu_registers_[reg]);
 #else