================
@@ -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);
----------------
cor3ntin wrote:
We do mark the loops `mustprogress` in C++ too.
I'm not sure how either of these attributes work, so I've try to preserve
existing behavior.
IE, a function will be marked `mustprogress` in C++11+ _unless_ at least one
loop is not `mustprogress`.
If you telling me that the `mustprogress` attribute has no effect in the
absence of loops in the body, or when all the loops are mustprogress, maybe we
should never use it in C++11+ modes?
https://github.com/llvm/llvm-project/pull/90066
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