================
@@ -908,6 +908,73 @@ void CodeGenFunction::EmitIfStmt(const IfStmt &S) {
incrementProfileCounter(&S);
}
+bool CodeGenFunction::checkIfLoopMustProgress(const Expr
*ControllingExpression,
+ bool IsTrivialCXXLoop) {
+ if (CGM.getCodeGenOpts().getFiniteLoops() ==
+ CodeGenOptions::FiniteLoopsKind::Always)
+ return true;
+ if (CGM.getCodeGenOpts().getFiniteLoops() ==
+ CodeGenOptions::FiniteLoopsKind::Never)
+ return false;
+
+ // Now apply rules for plain C (see 6.8.5.6 in C11).
+ // Loops with constant conditions do not have to make progress in any C
+ // version.
+ // As an extension, we consisider loops whose constant expression
+ // can be constant-folded.
+ Expr::EvalResult Result;
+ bool CondIsConstInt =
+ !ControllingExpression ||
+ (ControllingExpression->EvaluateAsInt(Result, getContext()) &&
+ Result.Val.isInt());
+ bool IsTrue = CondIsConstInt &&
+ (!ControllingExpression || Result.Val.getInt().getBoolValue());
+
+ if (getLangOpts().C99 && CondIsConstInt)
+ return false;
+
+ // Loops with non-constant conditions must make progress in C11 and later.
+ if (getLangOpts().C11)
+ return true;
+
+ // [C++26][intro.progress] (DR)
+ // The implementation may assume that any thread will eventually do one of
the
+ // following:
+ // [...]
+ // - continue execution of a trivial infinite loop ([stmt.iter.general]).
+ if (getLangOpts().CPlusPlus11) {
+ if (IsTrivialCXXLoop && IsTrue) {
+ CurFn->removeFnAttr(llvm::Attribute::MustProgress);
----------------
efriedma-quic wrote:
This doesn't have the effect you want. Even if you remove mustprogress from
the current function, we'll re-infer it if the caller is mustprogress.
You have two options here, I think:
- Introduce a call to llvm.sideeffect() (which dodges the whole issue because
it counts as a "side-effect" for mustprogress).
- Remove the mustprogress attribute from everything, and just mark individual
loops with mustprogress metadata, like we do in C.
https://github.com/llvm/llvm-project/pull/90066
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