[torque] Add constexpr int31 equality operator

This CL adds a constexpr int31 == operator that returns
a constexpr bool value.

It also fixes a bug that this introduces because branch generation
for ternary operators incorrectly assumed that the condition value
was bool, whereas it can also be constexpr bool now.

Change-Id: Ie7d3497c9d1112c121b4a29561fe065b5bf01fb6
Reviewed-on: https://chromium-review.googlesource.com/1106343
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Théotime Grohens <theotime@google.com>
Cr-Commit-Position: refs/heads/master@{#53867}

src/builtins/base.tq

@@ -250,6 +250,8 @@ extern operator '-' macro Int32Sub(int32, int32): int32;
 extern operator '*' macro Int32Mul(int32, int32): int32;
 extern operator '%' macro Int32Mod(int32, int32): int32;
 extern operator '&' macro Word32And(word32, word32): int32;
+extern operator '==' macro
+  ConstexprInt31Equal(constexpr int31, constexpr int31): constexpr bool;
 
 extern operator '==' macro Word32Equal(word32, word32): bool;
 extern operator '!=' macro Word32NotEqual(word32, word32): bool;

src/code-stub-assembler.h

@@ -2623,6 +2623,8 @@ class V8_EXPORT_PRIVATE CodeStubAssembler : public compiler::CodeAssembler {
 
   bool ConstexprBoolNot(bool value) { return !value; }
 
+  bool ConstexprInt31Equal(int31_t a, int31_t b) { return a == b; }
+
   void PerformStackCheck(TNode<Context> context);
 
  protected:

src/torque/implementation-visitor.cc

@@ -351,9 +351,10 @@ VisitResult ImplementationVisitor::Visit(ConditionalExpression* expr) {
 
     VisitResult condition_result = Visit(expr->condition);
     if (!condition_result.type()->IsNever()) {
+      condition_result =
+          GenerateImplicitConvert(TypeOracle::GetBoolType(), condition_result);
       GenerateBranch(condition_result, true_label, false_label);
     }
-
     GenerateLabelBind(true_label);
     GenerateIndent();
     source_out() << result->GetValueForWrite() << " = " << f1 << "();"