[liftoff] Add alternative names for unary conditions

Conditions are usually used in binary comparisons, and are named for
that purpose. When used in a unary comparison, {kEqual} means "equal to
zero" and {kUnequal} means "not equal to zero". This is noted in several
comments in {LiftoffCompiler}.

This CL introduces the alternative names {kEqualZero} and
{kNotEqualZero} to avoid the repeated comments and increase readability.

R=thibaudm@chromium.org

Bug: v8:12244
Change-Id: I720a3d91ea95a26a38a48c68161f1b0552937cd4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3172763Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76964}

src/wasm/baseline/liftoff-assembler.h

@@ -32,7 +32,9 @@ namespace wasm {
 
 enum LiftoffCondition {
   kEqual,
+  kEqualZero = kEqual,  // When used in a unary operation.
   kUnequal,
+  kNotEqualZero = kUnequal,  // When used in a unary operation.
   kSignedLessThan,
   kSignedLessEqual,
   kSignedGreaterThan,

src/wasm/baseline/liftoff-compiler.cc

@@ -842,8 +842,8 @@ class LiftoffCompiler {
       // Check if the number of calls is a power of 2.
       __ emit_i32_and(old_number_of_calls.gp(), old_number_of_calls.gp(),
                       new_number_of_calls.gp());
-      // Unary "unequal" means "different from zero".
-      __ emit_cond_jump(kUnequal, &no_tierup, kI32, old_number_of_calls.gp());
+      __ emit_cond_jump(kNotEqualZero, &no_tierup, kI32,
+                        old_number_of_calls.gp());
       TierUpFunction(decoder);
       // After the runtime call, the instance cache register is clobbered (we
       // reset it already in {SpillAllRegisters} above, but then we still access
@@ -1019,13 +1019,11 @@ class LiftoffCompiler {
       LOAD_INSTANCE_FIELD(flag, HookOnFunctionCallAddress, kSystemPointerSize,
                           {});
       __ Load(LiftoffRegister{flag}, flag, no_reg, 0, LoadType::kI32Load8U, {});
-      // Unary "unequal" means "not equals zero".
-      __ emit_cond_jump(kUnequal, &do_break, kI32, flag);
+      __ emit_cond_jump(kNotEqualZero, &do_break, kI32, flag);
 
       // Check if we should stop on "script entry".
       LOAD_INSTANCE_FIELD(flag, BreakOnEntry, kUInt8Size, {});
-      // Unary "equal" means "equals zero".
-      __ emit_cond_jump(kEqual, &no_break, kI32, flag);
+      __ emit_cond_jump(kEqualZero, &no_break, kI32, flag);
 
       __ bind(&do_break);
       EmitBreakpoint(decoder);
@@ -1274,11 +1272,10 @@ class LiftoffCompiler {
     // Test the condition, jump to else if zero.
     Register value = __ PopToRegister().gp();
     if (!has_outstanding_op()) {
-      // Unary "equal" means "equals zero".
-      __ emit_cond_jump(kEqual, if_block->else_state->label.get(), kI32, value);
+      __ emit_cond_jump(kEqualZero, if_block->else_state->label.get(), kI32,
+                        value);
     } else if (outstanding_op_ == kExprI32Eqz) {
-      // Unary "unequal" means "not equals zero".
-      __ emit_cond_jump(kUnequal, if_block->else_state->label.get(), kI32,
+      __ emit_cond_jump(kNotEqualZero, if_block->else_state->label.get(), kI32,
                         value);
       outstanding_op_ = kNoOutstandingOp;
     } else {
@@ -2506,11 +2503,9 @@ class LiftoffCompiler {
     Register value = __ PopToRegister().gp();
 
     if (!has_outstanding_op()) {
-      // Unary "equal" means "equals zero".
-      __ emit_cond_jump(kEqual, &cont_false, kI32, value);
+      __ emit_cond_jump(kEqualZero, &cont_false, kI32, value);
     } else if (outstanding_op_ == kExprI32Eqz) {
-      // Unary "unequal" means "not equals zero".
-      __ emit_cond_jump(kUnequal, &cont_false, kI32, value);
+      __ emit_cond_jump(kNotEqualZero, &cont_false, kI32, value);
       outstanding_op_ = kNoOutstandingOp;
     } else {
       // Otherwise, it's an i32 compare opcode.
@@ -2703,8 +2698,7 @@ class LiftoffCompiler {
       __ emit_u32_to_intptr(index_ptrsize, index_ptrsize);
     } else if (kSystemPointerSize == kInt32Size) {
       DCHECK_GE(kMaxUInt32, env_->max_memory_size);
-      // Unary "unequal" means "not equals zero".
-      __ emit_cond_jump(kUnequal, trap_label, kI32, index.high_gp());
+      __ emit_cond_jump(kNotEqualZero, trap_label, kI32, index.high_gp());
     }
 
     uintptr_t end_offset = offset + access_size - 1u;