================
@@ -263,6 +264,72 @@ static void terminateBody(CIRGenBuilderTy &builder,
mlir::Region &r,
b->erase();
}
+mlir::LogicalResult CIRGenFunction::emitIfStmt(const IfStmt &s) {
+ mlir::LogicalResult res = mlir::success();
+ // The else branch of a consteval if statement is always the only branch
+ // that can be runtime evaluated.
+ const Stmt *ConstevalExecuted;
+ if (s.isConsteval()) {
+ ConstevalExecuted = s.isNegatedConsteval() ? s.getThen() : s.getElse();
+ if (!ConstevalExecuted) {
+ // No runtime code execution required
+ return res;
+ }
+ }
+
+ // C99 6.8.4.1: The first substatement is executed if the expression
+ // compares unequal to 0. The condition must be a scalar type.
+ auto ifStmtBuilder = [&]() -> mlir::LogicalResult {
+ if (s.isConsteval())
+ return emitStmt(ConstevalExecuted, /*useCurrentScope=*/true);
+
+ if (s.getInit())
+ if (emitStmt(s.getInit(), /*useCurrentScope=*/true).failed())
+ return mlir::failure();
+
+ if (s.getConditionVariable())
+ emitDecl(*s.getConditionVariable());
+
+ // During LLVM codegen, if the condition constant folds and can be elided,
+ // it tries to avoid emitting the condition and the dead arm of the
if/else.
+ // TODO(cir): we skip this in CIRGen, but should implement this as part of
+ // SSCP or a specific CIR pass.
+ bool CondConstant;
+ if (ConstantFoldsToSimpleInteger(s.getCond(), CondConstant,
----------------
andykaylor wrote:
The only place the classic codegen calls `ConstantFoldsToSimpleInteger` that
isn't using the form with a Boolean result argument is in the switch statement
handling. That case is not folded in the CIR codegen in the incubator, with a
comment saying we prefer to keep it and let MLIR do the folding. @bcardosolopes
Wouldn't the same apply here and other places where conditions are constant
folded?
It looks like @keryell added the implementation here and maybe is needed in the
case of `constexpr`.
https://github.com/llvm/llvm-project/pull/134333
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