[clang] [CIR] Upstream lowering of conditional operators to TernaryOp (PR #138156)

[Erich Keane via cfe-commits]

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@@ -948,6 +950,165 @@ void CIRGenFunction::emitIgnoredExpr(const Expr *e) {
   emitLValue(e);
 }
 
+// Handle the case where the condition is a constant evaluatable simple integer,
+// which means we don't have to separately handle the true/false blocks.
+static std::optional<LValue> handleConditionalOperatorLValueSimpleCase(
+    CIRGenFunction &cgf, const AbstractConditionalOperator *e) {
+  const Expr *condExpr = e->getCond();
+  bool condExprBool;
+  if (cgf.constantFoldsToSimpleInteger(condExpr, condExprBool)) {
+    const Expr *live = e->getTrueExpr(), *dead = e->getFalseExpr();
+    if (!condExprBool)
+      std::swap(live, dead);
+
+    if (!cgf.containsLabel(dead)) {
+      // If the true case is live, we need to track its region.
+      if (condExprBool) {
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erichkeane wrote:

This is suspicious.  We've already swapped based on this, right?  So the association of dead/live/true/false is broken.

https://github.com/llvm/llvm-project/pull/138156