[flang] Preserve DeclareOp info in pre-cg-rewrite.

Currently, cg-rewrite removes the DeclareOp. As AddDebugInfo runs after
that, it cannot process the DeclareOp. My initial plan was to make the
AddDebugInfo pass run before the cg-rewrite but that has few issues.

1. Initially I was thinking to use the memref op to carry the variable
attr. But as @tblah suggested in the llvm#86939, it makes more sense to
carry that information on DeclareOp. It also makes it easy to handle it
in codegen and there is no special handling needed for arguments. For
that, we need to preserve the DeclareOp till the codegen.

2. Running earlier, we will miss the changes in passes that run between
cg-rewrite and codegen.

But not removing the DeclareOp in cg-rewrite has the issue that ShapeOp
remains and it causes errors during codegen. To solve this problem, I
convert DeclareOp to XDeclareOp in cg-rewrite instead of removing
it. This was mentioned as possible solution by @jeanPerier in
https://reviews.llvm.org/D136254

The conversion follows similar logic as used for other operators in that
file. The FortranAttr and CudaAttr are currently not converted but left
as TODO when the need arise. A later commit will use the XDeclareOp to
extract the variable information.

Author: abidh

flang/lib/Optimizer/CodeGen/CGOps.h renamed to flang/include/flang/Optimizer/CodeGen/CGOps.h

@@ -13,6 +13,7 @@
 #ifndef OPTIMIZER_CODEGEN_CGOPS_H
 #define OPTIMIZER_CODEGEN_CGOPS_H
 
+#include "flang/Optimizer/Dialect/FIRAttr.h"
 #include "flang/Optimizer/Dialect/FIRType.h"
 #include "mlir/Dialect/Func/IR/FuncOps.h"
 

flang/include/flang/Optimizer/CodeGen/CGOps.td

@@ -16,6 +16,8 @@
 
 include "mlir/IR/SymbolInterfaces.td"
 include "flang/Optimizer/Dialect/FIRTypes.td"
+include "flang/Optimizer/Dialect/FIRAttr.td"
+include "mlir/IR/BuiltinAttributes.td"
 
 def fircg_Dialect : Dialect {
   let name = "fircg";
@@ -202,4 +204,36 @@ def fircg_XArrayCoorOp : fircg_Op<"ext_array_coor", [AttrSizedOperandSegments]>
   }];
 }
 
+// Extended Declare operation.
+def fircg_XDeclareOp : fircg_Op<"ext_declare", [AttrSizedOperandSegments]> {
+  let summary = "for internal conversion only";
+
+  let description = [{
+    Prior to lowering to LLVM IR dialect, a DeclareOp will
+    be converted to an extended DeclareOp.
+  }];
+
+  let arguments = (ins
+    AnyRefOrBox:$memref,
+    Variadic<AnyIntegerType>:$shape,
+    Variadic<AnyIntegerType>:$shift,
+    Variadic<AnyIntegerType>:$typeparams,
+    Optional<fir_DummyScopeType>:$dummy_scope,
+    Builtin_StringAttr:$uniq_name
+  );
+  let results = (outs AnyRefOrBox);
+
+  let assemblyFormat = [{
+    $memref (`(` $shape^ `)`)? (`origin` $shift^)? (`typeparams` $typeparams^)?
+    (`dummy_scope` $dummy_scope^)?
+    attr-dict `:` functional-type(operands, results)
+  }];
+
+  let extraClassDeclaration = [{
+    // Shape is optional, but if it exists, it will be at offset 1.
+    unsigned shapeOffset() { return 1; }
+    unsigned shiftOffset() { return shapeOffset() + getShape().size(); }
+  }];
+}
+
 #endif

flang/lib/Optimizer/CodeGen/CGOps.cpp

@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "CGOps.h"
+#include "flang/Optimizer/CodeGen/CGOps.h"
 #include "flang/Optimizer/Dialect/FIRDialect.h"
 #include "flang/Optimizer/Dialect/FIROps.h"
 #include "flang/Optimizer/Dialect/FIRType.h"

flang/lib/Optimizer/CodeGen/CodeGen.cpp

@@ -12,7 +12,7 @@
 
 #include "flang/Optimizer/CodeGen/CodeGen.h"
 
-#include "CGOps.h"
+#include "flang/Optimizer/CodeGen/CGOps.h"
 #include "flang/Optimizer/CodeGen/CodeGenOpenMP.h"
 #include "flang/Optimizer/CodeGen/FIROpPatterns.h"
 #include "flang/Optimizer/CodeGen/TypeConverter.h"
@@ -170,6 +170,20 @@ genAllocationScaleSize(OP op, mlir::Type ity,
   return nullptr;
 }
 
+namespace {
+struct DeclareOpConversion : public fir::FIROpConversion<fir::cg::XDeclareOp> {
+public:
+  using FIROpConversion::FIROpConversion;
+  mlir::LogicalResult
+  matchAndRewrite(fir::cg::XDeclareOp declareOp, OpAdaptor adaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const override {
+    auto memRef = adaptor.getOperands()[0];
+    rewriter.replaceOp(declareOp, memRef);
+    return mlir::success();
+  }
+};
+} // namespace
+
 namespace {
 /// convert to LLVM IR dialect `alloca`
 struct AllocaOpConversion : public fir::FIROpConversion<fir::AllocaOp> {
@@ -3714,19 +3728,19 @@ void fir::populateFIRToLLVMConversionPatterns(
       BoxOffsetOpConversion, BoxProcHostOpConversion, BoxRankOpConversion,
       BoxTypeCodeOpConversion, BoxTypeDescOpConversion, CallOpConversion,
       CmpcOpConversion, ConstcOpConversion, ConvertOpConversion,
-      CoordinateOpConversion, DTEntryOpConversion, DivcOpConversion,
-      EmboxOpConversion, EmboxCharOpConversion, EmboxProcOpConversion,
-      ExtractValueOpConversion, FieldIndexOpConversion, FirEndOpConversion,
-      FreeMemOpConversion, GlobalLenOpConversion, GlobalOpConversion,
-      HasValueOpConversion, InsertOnRangeOpConversion, InsertValueOpConversion,
-      IsPresentOpConversion, LenParamIndexOpConversion, LoadOpConversion,
-      MulcOpConversion, NegcOpConversion, NoReassocOpConversion,
-      SelectCaseOpConversion, SelectOpConversion, SelectRankOpConversion,
-      SelectTypeOpConversion, ShapeOpConversion, ShapeShiftOpConversion,
-      ShiftOpConversion, SliceOpConversion, StoreOpConversion,
-      StringLitOpConversion, SubcOpConversion, TypeDescOpConversion,
-      TypeInfoOpConversion, UnboxCharOpConversion, UnboxProcOpConversion,
-      UndefOpConversion, UnreachableOpConversion,
+      CoordinateOpConversion, DTEntryOpConversion, DeclareOpConversion,
+      DivcOpConversion, EmboxOpConversion, EmboxCharOpConversion,
+      EmboxProcOpConversion, ExtractValueOpConversion, FieldIndexOpConversion,
+      FirEndOpConversion, FreeMemOpConversion, GlobalLenOpConversion,
+      GlobalOpConversion, HasValueOpConversion, InsertOnRangeOpConversion,
+      InsertValueOpConversion, IsPresentOpConversion, LenParamIndexOpConversion,
+      LoadOpConversion, MulcOpConversion, NegcOpConversion,
+      NoReassocOpConversion, SelectCaseOpConversion, SelectOpConversion,
+      SelectRankOpConversion, SelectTypeOpConversion, ShapeOpConversion,
+      ShapeShiftOpConversion, ShiftOpConversion, SliceOpConversion,
+      StoreOpConversion, StringLitOpConversion, SubcOpConversion,
+      TypeDescOpConversion, TypeInfoOpConversion, UnboxCharOpConversion,
+      UnboxProcOpConversion, UndefOpConversion, UnreachableOpConversion,
       UnrealizedConversionCastOpConversion, XArrayCoorOpConversion,
       XEmboxOpConversion, XReboxOpConversion, ZeroOpConversion>(converter,
                                                                 options);

flang/lib/Optimizer/CodeGen/PreCGRewrite.cpp

@@ -12,8 +12,8 @@
 
 #include "flang/Optimizer/CodeGen/CodeGen.h"
 
-#include "CGOps.h"
 #include "flang/Optimizer/Builder/Todo.h" // remove when TODO's are done
+#include "flang/Optimizer/CodeGen/CGOps.h"
 #include "flang/Optimizer/Dialect/FIRDialect.h"
 #include "flang/Optimizer/Dialect/FIROps.h"
 #include "flang/Optimizer/Dialect/FIRType.h"
@@ -276,7 +276,29 @@ class DeclareOpConversion : public mlir::OpRewritePattern<fir::DeclareOp> {
   mlir::LogicalResult
   matchAndRewrite(fir::DeclareOp declareOp,
                   mlir::PatternRewriter &rewriter) const override {
-    rewriter.replaceOp(declareOp, declareOp.getMemref());
+    auto loc = declareOp.getLoc();
+    llvm::SmallVector<mlir::Value> shapeOpers;
+    llvm::SmallVector<mlir::Value> shiftOpers;
+    if (auto shapeVal = declareOp.getShape()) {
+      if (auto shapeOp = mlir::dyn_cast<fir::ShapeOp>(shapeVal.getDefiningOp()))
+        populateShape(shapeOpers, shapeOp);
+      else if (auto shiftOp =
+                   mlir::dyn_cast<fir::ShapeShiftOp>(shapeVal.getDefiningOp()))
+        populateShapeAndShift(shapeOpers, shiftOpers, shiftOp);
+      else if (auto shiftOp =
+                   mlir::dyn_cast<fir::ShiftOp>(shapeVal.getDefiningOp()))
+        populateShift(shiftOpers, shiftOp);
+      else
+        return mlir::failure();
+    }
+    // FIXME: Add FortranAttrs and CudaAttrs
+    auto xDeclOp = rewriter.create<fir::cg::XDeclareOp>(
+        loc, declareOp.getType(), declareOp.getMemref(), shapeOpers, shiftOpers,
+        declareOp.getTypeparams(), declareOp.getDummyScope(),
+        declareOp.getUniqName());
+    LLVM_DEBUG(llvm::dbgs()
+               << "rewriting " << declareOp << " to " << xDeclOp << '\n');
+    rewriter.replaceOp(declareOp, xDeclOp.getOperation()->getResults());
     return mlir::success();
   }
 };

flang/test/Fir/declare-codegen.fir

@@ -17,7 +17,8 @@ func.func private @bar(%arg0: !fir.ref<!fir.array<12x23xi32>>)
 
 // CHECK-LABEL: func.func @test(
 // CHECK-SAME: %[[arg0:.*]]: !fir.ref<!fir.array<12x23xi32>>) {
-// CHECK-NEXT: fir.call @bar(%[[arg0]]) : (!fir.ref<!fir.array<12x23xi32>>) -> ()
+// CHECK: fircg.ext_declare
+
 
 func.func @useless_shape_with_duplicate_extent_operand(%arg0: !fir.ref<!fir.array<3x3xf32>>) {
   %c3 = arith.constant 3 : index
@@ -27,4 +28,4 @@ func.func @useless_shape_with_duplicate_extent_operand(%arg0: !fir.ref<!fir.arra
 }
 
 // CHECK-LABEL: func.func @useless_shape_with_duplicate_extent_operand(
-// CHECK-NEXT: return
+// CHECK: fircg.ext_declare

flang/test/Fir/dummy-scope-codegen.fir

@@ -6,4 +6,4 @@ func.func @dummy_scope(%arg0: !fir.ref<f32>) {
   return
 }
 // CHECK-LABEL: func.func @dummy_scope(
-// CHECK-NEXT: return
+// CHECK: fircg.ext_declare