[Liftoff] [ia32] Optimize stack limit check on ia32

On ia32, we can encode the address of the stack limit in the operand
directly, saving one mov instruction and reducing register pressure.

R=titzer@chromium.org

Bug: v8:6600
Change-Id: I2742efbfea16d56d648c233a2dba1d8672dc489d
Reviewed-on: https://chromium-review.googlesource.com/930961
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51463}

src/ia32/assembler-ia32-inl.h

@@ -315,12 +315,6 @@ void Operand::set_disp8(int8_t disp) {
   *reinterpret_cast<int8_t*>(&buf_[len_++]) = disp;
 }
 
-
-Operand::Operand(Immediate imm) {
-  // [disp/r]
-  set_modrm(0, ebp);
-  set_dispr(imm.immediate(), imm.rmode_);
-}
 }  // namespace internal
 }  // namespace v8
 

src/ia32/assembler-ia32.h

@@ -341,7 +341,10 @@ class Operand BASE_EMBEDDED {
   }
 
   // [disp/r]
-  INLINE(explicit Operand(Immediate imm));
+  INLINE(explicit Operand(Immediate imm)) {
+    set_modrm(0, ebp);
+    set_dispr(imm.immediate(), imm.rmode_);
+  }
 
   // [base + disp/r]
   explicit Operand(Register base, int32_t disp,

src/wasm/baseline/ia32/liftoff-assembler-ia32.h

@@ -669,9 +669,8 @@ void LiftoffAssembler::emit_i32_set_cond(Condition cond, Register dst,
 }
 
 void LiftoffAssembler::StackCheck(Label* ool_code) {
-  Register limit = GetUnusedRegister(kGpReg).gp();
-  mov(limit, Immediate(ExternalReference::address_of_stack_limit(isolate())));
-  cmp(esp, Operand(limit, 0));
+  cmp(esp,
+      Operand(Immediate(ExternalReference::address_of_stack_limit(isolate()))));
   j(below_equal, ool_code);
 }