Fix code generation failures on MIPS

On MIPS and MIPS64, UseScratchRegisterScope has only one register for the scratch register [1,2],
and TurboAssembler::CallCFunctionHelper runs out of it as fast_c_call_caller_fp_address
uses the register. That causes code generation failures.

As a workaround, this CL reduces the number of nested UseScratchRegisterScope where
the code generation is failing.

[1]: https://chromium.googlesource.com/v8/v8.git/+/dde25872f58951bb0148cf43d6a504ab2f280485/src/mips/assembler-mips.cc#310
[2]: https://chromium.googlesource.com/v8/v8.git/+/dde25872f58951bb0148cf43d6a504ab2f280485/src/mips64/assembler-mips64.cc#287

Change-Id: I0813c656cafdb09ccd6f53d51f3620385e00022f
Reviewed-on: https://chromium-review.googlesource.com/c/1379590Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58344}

src/mips/macro-assembler-mips.cc

@@ -5422,9 +5422,8 @@ void TurboAssembler::CallCFunctionHelper(Register function_base,
     // Save the frame pointer and PC so that the stack layout remains iterable,
     // even without an ExitFrame which normally exists between JS and C frames.
     if (isolate() != nullptr) {
-      UseScratchRegisterScope temps(this);
-      Register scratch1 = temps.Acquire();
       // 't' registers are caller-saved so this is safe as a scratch register.
+      Register scratch1 = t4;
       Register scratch2 = t5;
       DCHECK(!AreAliased(scratch1, scratch2, function_base));
 
@@ -5446,8 +5445,7 @@ void TurboAssembler::CallCFunctionHelper(Register function_base,
 
     if (isolate() != nullptr) {
       // We don't unset the PC; the FP is the source of truth.
-      UseScratchRegisterScope temps(this);
-      Register scratch = temps.Acquire();
+      Register scratch = t4;
       li(scratch, ExternalReference::fast_c_call_caller_fp_address(isolate()));
       sw(zero_reg, MemOperand(scratch));
     }

src/mips64/macro-assembler-mips64.cc

@@ -5787,9 +5787,8 @@ void TurboAssembler::CallCFunctionHelper(Register function,
     // Save the frame pointer and PC so that the stack layout remains iterable,
     // even without an ExitFrame which normally exists between JS and C frames.
     if (isolate() != nullptr) {
-      UseScratchRegisterScope temps(this);
-      Register scratch1 = temps.Acquire();
       // 't' registers are caller-saved so this is safe as a scratch register.
+      Register scratch1 = t1;
       Register scratch2 = t2;
       DCHECK(!AreAliased(scratch1, scratch2, function));
 
@@ -5811,8 +5810,7 @@ void TurboAssembler::CallCFunctionHelper(Register function,
 
     if (isolate() != nullptr) {
       // We don't unset the PC; the FP is the source of truth.
-      UseScratchRegisterScope temps(this);
-      Register scratch = temps.Acquire();
+      Register scratch = t1;
       li(scratch, ExternalReference::fast_c_call_caller_fp_address(isolate()));
       Sd(zero_reg, MemOperand(scratch));
     }