MIPS: Fix 'MIPS: Support r6 max, min floating point instructions.'

Port d4a391bb

Add SmiTag()/smiUntag() calls to make values on stack GC-safe.

Original commit message:
Use macro instructions for min, max ops to get the same functionality on
pre-r6 and r6 targets.

BUG=chromium:598651
LOG=N

Review URL: https://codereview.chromium.org/1842833002

Cr-Commit-Position: refs/heads/master@{#35130}

src/mips/builtins-mips.cc

@@ -180,6 +180,8 @@ void Builtins::Generate_MathMaxMin(MacroAssembler* masm, MathMaxMinKind kind) {
     {
       // Parameter is not a Number, use the ToNumberStub to convert it.
       FrameScope scope(masm, StackFrame::INTERNAL);
+      __ SmiTag(a0);
+      __ SmiTag(a3);
       __ Push(a0, a1, a3);
       __ mov(a0, a2);
       ToNumberStub stub(masm->isolate());
@@ -196,6 +198,8 @@ void Builtins::Generate_MathMaxMin(MacroAssembler* masm, MathMaxMinKind kind) {
         __ SmiToDoubleFPURegister(a1, f0, t0);
         __ bind(&done_restore);
       }
+      __ SmiUntag(a3);
+      __ SmiUntag(a0);
     }
     __ jmp(&convert);
     __ bind(&convert_number);

src/mips64/builtins-mips64.cc

@@ -179,6 +179,8 @@ void Builtins::Generate_MathMaxMin(MacroAssembler* masm, MathMaxMinKind kind) {
     {
       // Parameter is not a Number, use the ToNumberStub to convert it.
       FrameScope scope(masm, StackFrame::INTERNAL);
+      __ SmiTag(a0);
+      __ SmiTag(a3);
       __ Push(a0, a1, a3);
       __ mov(a0, a2);
       ToNumberStub stub(masm->isolate());
@@ -195,6 +197,8 @@ void Builtins::Generate_MathMaxMin(MacroAssembler* masm, MathMaxMinKind kind) {
         __ SmiToDoubleFPURegister(a1, f0, a4);
         __ bind(&done_restore);
       }
+      __ SmiUntag(a3);
+      __ SmiUntag(a0);
     }
     __ jmp(&convert);
     __ bind(&convert_number);