[flang-commits] [flang] [flang] Simplify hlfir.index in a few limited cases. (PR #161558)

[via flang-commits]

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@@ -2284,6 +2284,262 @@ class CmpCharOpConversion : public mlir::OpRewritePattern<hlfir::CmpCharOp> {
   }
 };
 
+static std::pair<mlir::Value, hlfir::AssociateOp>
+getVariable(fir::FirOpBuilder &builder, mlir::Location loc, mlir::Value val) {
+  // If it is an expression - create a variable from it, or forward
+  // the value otherwise.
+  hlfir::AssociateOp associate;
+  if (!mlir::isa<hlfir::ExprType>(val.getType()))
+    return {val, associate};
+  hlfir::Entity entity{val};
+  mlir::NamedAttribute byRefAttr = fir::getAdaptToByRefAttr(builder);
+  associate = hlfir::genAssociateExpr(loc, builder, entity, entity.getType(),
+                                      "", byRefAttr);
+  return {associate.getBase(), associate};
+}
+
+// Return character length if known at compile time. Unlike genCharLength
+// it does not create any new op as specifically is intended for analysis.
+// It is inspired by genLengthParameters that does the job for genCharLength.
+static std::optional<std::int64_t> getCharLengthIfConst(hlfir::Entity entity) {
+  if (!entity.isCharacter()) {
+    return std::nullopt;
+  }
+
+  if (mlir::isa<hlfir::ExprType>(entity.getType())) {
+    mlir::Value expr = entity;
+    if (auto reassoc = expr.getDefiningOp<hlfir::NoReassocOp>())
+      expr = reassoc.getVal();
+    // Going through fir::ExtendedValue would create a temp,
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jeanPerier wrote:

Can you move the getCharLengthIfConst helper to HLFIRTools so that you can share the piece of code about hlfir::Expr with the similar one in `hlfir::genLengthParameters` for easier maintenance.

It is also a rather useful tool to have for other passes/analysis dealing with characters.

https://github.com/llvm/llvm-project/pull/161558