[fir] Add conversion patterns for slice, shape, shapeshift and shift ops

[clementval]

Summary

The information in these perations is used by other operation.
At this point they should not have anymore uses.

This patch is part of the upstreaming effort from fir-dev branch.

Co-authored-by: Eric Schweitz <[e-mail]>
Co-authored-by: Jean Perier <[e-mail]>

[kiranchandramohan]

Can you add a TODO to investigate why DCE leaves these ops around? If there is an original test case that will also be helpful for future investigation.

flang/lib/Optimizer/CodeGen/CodeGen.cpp

1394

Should this be a notify failure?

[clementval]

In D113971#3134347, @kiranchandramohan wrote:

Can you add a TODO to investigate why DCE leaves these ops around? If there is an original test case that will also be helpful for future investigation.

AFAIK it does not leave them around. These conversion patterns are just here to make sure that at the end of this pass these ops have been made dead and removed.

flang/lib/Optimizer/CodeGen/CodeGen.cpp

1394

Yeah can switch to notifyMatchFailure. I'll add a invalid test as well.

[clementval]

Switch to notifyMatchFailure + add invalid tests

[clementval]

Rebase

[kiranchandramohan]

LGTM.

flang/lib/Optimizer/CodeGen/CodeGen.cpp

1382

Nit: If it is the pre-codegen pass that ensures this then it might be good to mention that here.

[clementval]

Rebase + add comment

flang/lib/Optimizer/CodeGen/CodeGen.cpp

matchAndRewrite(fir::NegcOp neg, OpAdaptor adaptor,
     auto nrp = rewriter.create<mlir::LLVM::FNegOp>(loc, eleTy, rp);
     auto nip = rewriter.create<mlir::LLVM::FNegOp>(loc, eleTy, ip);
     auto r = rewriter.create<mlir::LLVM::InsertValueOp>(loc, ty, o0, nrp, c0);
     rewriter.replaceOpWithNewOp<mlir::LLVM::InsertValueOp>(neg, ty, r, nip, c1);
     return success();
   }
 };
 
+/// Conversion pattern for operation that must be dead. The information in these
+/// operations is used by other operation. At this point they should not have
+/// anymore uses.
+template <typename FromOp>
+struct MustBeDeadConversion : public FIROpConversion<FromOp> {
+  explicit MustBeDeadConversion(fir::LLVMTypeConverter &lowering)
+      : FIROpConversion<FromOp>(lowering) {}
+  using OpAdaptor = typename FromOp::Adaptor;
+
+  mlir::LogicalResult
+  matchAndRewrite(FromOp op, OpAdaptor adaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const final {
+    if (!op->getUses().empty())
+      return mlir::emitError(op.getLoc(), "op must be dead");
+    rewriter.eraseOp(op);
+    return success();
+  }
+};
+
+struct ShapeOpConversion : public MustBeDeadConversion<fir::ShapeOp> {
+  using MustBeDeadConversion::MustBeDeadConversion;
+};
+
+struct ShapeShiftOpConversion : public MustBeDeadConversion<fir::ShapeShiftOp> {
+  using MustBeDeadConversion::MustBeDeadConversion;
+};
+
+struct ShiftOpConversion : public MustBeDeadConversion<fir::ShiftOp> {
+  using MustBeDeadConversion::MustBeDeadConversion;
+};
+
+struct SliceOpConversion : public MustBeDeadConversion<fir::SliceOp> {
+  using MustBeDeadConversion::MustBeDeadConversion;
+};
+
 /// `fir.is_present` -->
 /// ```
 ///  %0 = llvm.mlir.constant(0 : i64)
 ///  %1 = llvm.ptrtoint %0
 ///  %2 = llvm.icmp "ne" %1, %0 : i64
 /// ```
 struct IsPresentOpConversion : public FIROpConversion<fir::IsPresentOp> {
   using FIROpConversion::FIROpConversion;
pattern.insert<
         BoxEleSizeOpConversion, BoxIsAllocOpConversion, BoxIsArrayOpConversion,
         BoxIsPtrOpConversion, BoxRankOpConversion, CallOpConversion,
         ConvertOpConversion, DispatchOpConversion, DispatchTableOpConversion,
         DTEntryOpConversion, DivcOpConversion, EmboxCharOpConversion,
         ExtractValueOpConversion, HasValueOpConversion, GlobalLenOpConversion,
         GlobalOpConversion, InsertOnRangeOpConversion, InsertValueOpConversion,
         IsPresentOpConversion, LoadOpConversion, NegcOpConversion,
         MulcOpConversion, SelectCaseOpConversion, SelectOpConversion,
-        SelectRankOpConversion, SelectTypeOpConversion, StoreOpConversion,
-        SubcOpConversion, UnboxCharOpConversion, UndefOpConversion,
-        UnreachableOpConversion, ZeroOpConversion>(typeConverter);
+        SelectRankOpConversion, SelectTypeOpConversion, ShapeOpConversion,
+        ShapeShiftOpConversion, ShiftOpConversion, SliceOpConversion,
+        StoreOpConversion, SubcOpConversion, UnboxCharOpConversion,
+        UndefOpConversion, UnreachableOpConversion, ZeroOpConversion>(
+        typeConverter);
     mlir::populateStdToLLVMConversionPatterns(typeConverter, pattern);
     mlir::arith::populateArithmeticToLLVMConversionPatterns(typeConverter,
                                                             pattern);
     mlir::ConversionTarget target{*context};
     target.addLegalDialect<mlir::LLVM::LLVMDialect>();
 
     // required NOPs for applying a full conversion
     target.addLegalOp<mlir::ModuleOp>();

flang/test/Fir/convert-to-llvm.fir

func @absent() -> i1 {
   return %1 : i1
 }
 
 // CHECK-LABEL: @absent
 // CHECK-SAME:  () -> i1
 // CHECK-NEXT:  %[[ptr:.*]] = llvm.mlir.null : !llvm.ptr<i64>
 // CHECK-NEXT:  %[[ret_val:.*]] = llvm.call @is_present(%[[ptr]]) : (!llvm.ptr<i64>) -> i1
 // CHECK-NEXT:  llvm.return %[[ret_val]] : i1
+
+// -----
+
+// Test must be dead conversion.
+
+func @dead_shift() {
+  %c0 = arith.constant 0 : index
+  %0 = fir.shift %c0 : (index) -> !fir.shift<1>
+  return
+}
+
+// CHECK-LABEL: llvm.func @dead_shift
+// CHECK-NOT: fir.shift
+// CHECK: %{{.*}} = llvm.mlir.constant(0 : index) : i{{.*}}
+// CHECK-NEXT: llvm.return
+
+func @dead_shape() {
+  %c0 = arith.constant 0 : index
+  %0 = fir.shape %c0 : (index) -> !fir.shape<1>
+  return
+}
+
+// CHECK-LABEL: llvm.func @dead_shape
+// CHECK-NOT: fir.shape
+// CHECK: %{{.*}} = llvm.mlir.constant(0 : index) : i{{.*}}
+// CHECK-NEXT: llvm.return
+
+func @dead_shapeshift() {
+  %c0 = arith.constant 0 : index
+  %0 = fir.shape_shift %c0, %c0 : (index, index) -> !fir.shapeshift<1>
+  return
+}
+
+// CHECK-LABEL: llvm.func @dead_shapeshift
+// CHECK-NOT: fir.shape_shift
+// CHECK: %{{.*}} = llvm.mlir.constant(0 : index) : i{{.*}}
+// CHECK-NEXT: llvm.return
+
+func @dead_slice() {
+  %c0 = arith.constant 0 : index
+  %0 = fir.slice %c0, %c0, %c0 : (index, index, index) -> !fir.slice<1>
+  return
+}
+
+// CHECK-LABEL: llvm.func @dead_slice
+// CHECK-NOT: fir.slice
+// CHECK: %{{.*}} = llvm.mlir.constant(0 : index) : i{{.*}}
+// CHECK-NEXT: llvm.return