MIPS: Fix '[runtime] Optimize and unify rest parameters.'

Fixes a register-clobbering problem. The Branch() instruction can overwrite the 'at' register, so it can't be used as scratch in Allocate(). Added DCHECK to avoid this in the future.

BUG=

Review URL: https://codereview.chromium.org/1687173006

Cr-Commit-Position: refs/heads/master@{#33912}

src/mips/code-stubs-mips.cc

@@ -5242,7 +5242,7 @@ void FastNewRestParameterStub::Generate(MacroAssembler* masm) {
     Label allocate, done_allocate;
     __ li(a1, Operand(JSArray::kSize + FixedArray::kHeaderSize));
     __ Lsa(a1, a1, a0, kPointerSizeLog2 - 1);
-    __ Allocate(a1, v0, a3, at, &allocate, TAG_OBJECT);
+    __ Allocate(a1, v0, a3, t0, &allocate, TAG_OBJECT);
     __ bind(&done_allocate);
 
     // Setup the elements array in v0.

src/mips/macro-assembler-mips.cc

@@ -3333,7 +3333,7 @@ void MacroAssembler::Allocate(int object_size,
     return;
   }
 
-  DCHECK(!AreAliased(result, scratch1, scratch2, t9));
+  DCHECK(!AreAliased(result, scratch1, scratch2, t9, at));
 
   // Make object size into bytes.
   if ((flags & SIZE_IN_WORDS) != 0) {
@@ -3419,8 +3419,8 @@ void MacroAssembler::Allocate(Register object_size, Register result,
 
   // |object_size| and |result_end| may overlap if the DOUBLE_ALIGNMENT flag
   // is not specified. Other registers must not overlap.
-  DCHECK(!AreAliased(object_size, result, scratch, t9));
-  DCHECK(!AreAliased(result_end, result, scratch, t9));
+  DCHECK(!AreAliased(object_size, result, scratch, t9, at));
+  DCHECK(!AreAliased(result_end, result, scratch, t9, at));
   DCHECK((flags & DOUBLE_ALIGNMENT) == 0 || !object_size.is(result_end));
 
   // Check relative positions of allocation top and limit addresses.

src/mips64/code-stubs-mips64.cc

@@ -5258,7 +5258,7 @@ void FastNewRestParameterStub::Generate(MacroAssembler* masm) {
     Label allocate, done_allocate;
     __ li(a1, Operand(JSArray::kSize + FixedArray::kHeaderSize));
     __ Dlsa(a1, a1, a0, kPointerSizeLog2);
-    __ Allocate(a1, v0, a3, at, &allocate, TAG_OBJECT);
+    __ Allocate(a1, v0, a3, a4, &allocate, TAG_OBJECT);
     __ bind(&done_allocate);
 
     // Compute arguments.length in a4.

src/mips64/macro-assembler-mips64.cc

@@ -3770,7 +3770,7 @@ void MacroAssembler::Allocate(int object_size,
     return;
   }
 
-  DCHECK(!AreAliased(result, scratch1, scratch2, t9));
+  DCHECK(!AreAliased(result, scratch1, scratch2, t9, at));
 
   // Make object size into bytes.
   if ((flags & SIZE_IN_WORDS) != 0) {
@@ -3848,8 +3848,8 @@ void MacroAssembler::Allocate(Register object_size, Register result,
   }
 
   // |object_size| and |result_end| may overlap, other registers must not.
-  DCHECK(!AreAliased(object_size, result, scratch, t9));
-  DCHECK(!AreAliased(result_end, result, scratch, t9));
+  DCHECK(!AreAliased(object_size, result, scratch, t9, at));
+  DCHECK(!AreAliased(result_end, result, scratch, t9, at));
 
   // Check relative positions of allocation top and limit addresses.
   // ARM adds additional checks to make sure the ldm instruction can be