[flang][NFC] Unify getIfConstantIntValue helpers

[tblah]

There were different helpers for attempting to fetch compile time constants from MLIR: one in fir::getIntIfConstant and one in CodeGen. Unify the two.

[llvmbot]

@llvm/pr-subscribers-flang-fir-hlfir

@llvm/pr-subscribers-flang-codegen

Author: Tom Eccles (tblah)

Changes

I would like to re-use this function in a subsequent patch. I picked fir::factory because that seemed to contain various free functions that don't need to be in FirOpBuilder. This might be better as a static method of FirOpBuilder - I'm unsure.

---

Full diff: https://github.com/llvm/llvm-project/pull/87633.diff

3 Files Affected:

• (modified) flang/include/flang/Optimizer/Builder/FIRBuilder.h (+4)
• (modified) flang/lib/Optimizer/Builder/FIRBuilder.cpp (+15)
• (modified) flang/lib/Optimizer/CodeGen/CodeGen.cpp (+2-19)

diff --git a/flang/include/flang/Optimizer/Builder/FIRBuilder.h b/flang/include/flang/Optimizer/Builder/FIRBuilder.h
index 940866b25d2fe8..8993559eca2ef9 100644
--- a/flang/include/flang/Optimizer/Builder/FIRBuilder.h
+++ b/flang/include/flang/Optimizer/Builder/FIRBuilder.h
@@ -695,6 +695,10 @@ mlir::Value createNullBoxProc(fir::FirOpBuilder &builder, mlir::Location loc,
 
 /// Set internal linkage attribute on a function.
 void setInternalLinkage(mlir::func::FuncOp);
+
+/// Extract constant from a value if it is a result of one of the ConstantOp
+/// operations, otherwise, return std::nullopt.
+std::optional<int64_t> getIfConstantIntValue(mlir::Value val);
 } // namespace fir::factory
 
 #endif // FORTRAN_OPTIMIZER_BUILDER_FIRBUILDER_H
diff --git a/flang/lib/Optimizer/Builder/FIRBuilder.cpp b/flang/lib/Optimizer/Builder/FIRBuilder.cpp
index e4362b2f9e6945..4e4c79bc8c03aa 100644
--- a/flang/lib/Optimizer/Builder/FIRBuilder.cpp
+++ b/flang/lib/Optimizer/Builder/FIRBuilder.cpp
@@ -1584,3 +1584,18 @@ void fir::factory::setInternalLinkage(mlir::func::FuncOp func) {
       mlir::LLVM::LinkageAttr::get(func->getContext(), internalLinkage);
   func->setAttr("llvm.linkage", linkage);
 }
+
+std::optional<int64_t> fir::factory::getIfConstantIntValue(mlir::Value val) {
+  if (!val || !val.dyn_cast<mlir::OpResult>())
+    return {};
+
+  mlir::Operation *defop = val.getDefiningOp();
+
+  if (auto constOp = mlir::dyn_cast<mlir::arith::ConstantIntOp>(defop))
+    return constOp.value();
+  if (auto llConstOp = mlir::dyn_cast<mlir::LLVM::ConstantOp>(defop))
+    if (auto attr = llConstOp.getValue().dyn_cast<mlir::IntegerAttr>())
+      return attr.getValue().getSExtValue();
+
+  return {};
+}
\ No newline at end of file
diff --git a/flang/lib/Optimizer/CodeGen/CodeGen.cpp b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
index 06ce84f1543a3f..526cad884df881 100644
--- a/flang/lib/Optimizer/CodeGen/CodeGen.cpp
+++ b/flang/lib/Optimizer/CodeGen/CodeGen.cpp
@@ -92,27 +92,10 @@ static mlir::Block *createBlock(mlir::ConversionPatternRewriter &rewriter,
                               mlir::Region::iterator(insertBefore));
 }
 
-/// Extract constant from a value if it is a result of one of the
-/// ConstantOp operations, otherwise, return std::nullopt.
-static std::optional<int64_t> getIfConstantIntValue(mlir::Value val) {
-  if (!val || !val.dyn_cast<mlir::OpResult>())
-    return {};
-
-  mlir::Operation *defop = val.getDefiningOp();
-
-  if (auto constOp = mlir::dyn_cast<mlir::arith::ConstantIntOp>(defop))
-    return constOp.value();
-  if (auto llConstOp = mlir::dyn_cast<mlir::LLVM::ConstantOp>(defop))
-    if (auto attr = llConstOp.getValue().dyn_cast<mlir::IntegerAttr>())
-      return attr.getValue().getSExtValue();
-
-  return {};
-}
-
 /// Extract constant from a value that must be the result of one of the
 /// ConstantOp operations.
 static int64_t getConstantIntValue(mlir::Value val) {
-  if (auto constVal = getIfConstantIntValue(val))
+  if (auto constVal = fir::factory::getIfConstantIntValue(val))
     return *constVal;
   fir::emitFatalError(val.getLoc(), "must be a constant");
 }
@@ -664,7 +647,7 @@ struct ConvertOpConversion : public fir::FIROpConversion<fir::ConvertOp> {
                << " -> " << toTy;
 
       // Do folding for constant inputs.
-      if (auto constVal = getIfConstantIntValue(op0)) {
+      if (auto constVal = fir::factory::getIfConstantIntValue(op0)) {
         mlir::Value normVal =
             genConstantIndex(loc, toTy, rewriter, *constVal ? 1 : 0);
         rewriter.replaceOp(convert, normVal);

[jeanPerier]

There is actually fir::getIntIfConstant that is doing a similar job except it does not handle the LLVM::ConstantOp (which needs to be handled on codegen).

Could you merge them so that there is a single helper?

[jeanPerier]

Shouldn't this declaration be removed?