[fir] Add fir.constc conversion

[rovka]

Summary

Add the codegen for fir.constc.

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

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

[awarzynski]

flang/lib/Optimizer/CodeGen/CodeGen.cpp

569

Could you add a short comment for this struct?

579–586

It would really help me to understand the logic here if the names were more descriptive :) For example, what's ri and ii? And what's the difference between r and rr?

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

696

[nit] How about different KIND?

[kiranchandramohan]

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

695

I think we do not have this op in fir-ops.fir where we check all the ops. Could you add a similar one there as well?

[tschuett]

flang/lib/Optimizer/CodeGen/CodeGen.cpp

1654

Would it help to put // clang-format off around this block, with one entry per line. It is hard to see the real diff.

[clementval]

flang/lib/Optimizer/CodeGen/CodeGen.cpp

1654

It's changing a lot recently because we are upstreaming the conversion patterns. Once we are done it will not change much so I don't think we need to format it differently.

[rovka]

+ comment
+ test for kind = 8 (I don't think we need to cover all of them here, all the other complex ops only use kind = 16)
+ (hopefully) better names for variables

[rovka]

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

695

Great idea, I'll send a separate patch because we actually hit an unreachable while printing constc

[rovka]

Rebase so the premerge CI can run.

[kiranchandramohan]

LGTM.

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

695

OK

[awarzynski]

LGTM, thanks for addressing my comments!

flang/lib/Optimizer/CodeGen/CodeGen.cpp

matchAndRewrite(fir::CmpcOp cmp, OpAdaptor adaptor,
     default:
       rewriter.replaceOp(cmp, rcp.getResult());
       break;
     }
     return success();
   }
 };
 
+struct ConstcOpConversion : public FIROpConversion<fir::ConstcOp> {
+  using FIROpConversion::FIROpConversion;
+
+  mlir::LogicalResult
+  matchAndRewrite(fir::ConstcOp conc, OpAdaptor,
+                  mlir::ConversionPatternRewriter &rewriter) const override {
+    mlir::Location loc = conc.getLoc();
+    mlir::MLIRContext *ctx = conc.getContext();
+    mlir::Type ty = convertType(conc.getType());
+    mlir::Type ety = convertType(getComplexEleTy(conc.getType()));
+    auto ri = mlir::FloatAttr::get(ety, getValue(conc.getReal()));
+    auto rp = rewriter.create<mlir::LLVM::ConstantOp>(loc, ety, ri);
+    auto ii = mlir::FloatAttr::get(ety, getValue(conc.getImaginary()));
+    auto ip = rewriter.create<mlir::LLVM::ConstantOp>(loc, ety, ii);
+    auto c0 = mlir::ArrayAttr::get(ctx, rewriter.getI32IntegerAttr(0));
+    auto c1 = mlir::ArrayAttr::get(ctx, rewriter.getI32IntegerAttr(1));
+    auto r = rewriter.create<mlir::LLVM::UndefOp>(loc, ty);
+    auto rr = rewriter.create<mlir::LLVM::InsertValueOp>(loc, ty, r, rp, c0);
+    rewriter.replaceOpWithNewOp<mlir::LLVM::InsertValueOp>(conc, ty, rr, ip,
+                                                           c1);
+    return success();
+  }
+
+  inline APFloat getValue(mlir::Attribute attr) const {
+    return attr.cast<fir::RealAttr>().getValue();
+  }
+};
+
 /// convert value of from-type to value of to-type
 struct ConvertOpConversion : public FIROpConversion<fir::ConvertOp> {
   using FIROpConversion::FIROpConversion;
 
   static bool isFloatingPointTy(mlir::Type ty) {
     return ty.isa<mlir::FloatType>();
   }
 
void runOnOperation() override final {
     auto mod = getModule();
     if (!forcedTargetTriple.empty()) {
       fir::setTargetTriple(mod, forcedTargetTriple);
     }
 
     auto *context = getModule().getContext();
     fir::LLVMTypeConverter typeConverter{getModule()};
     mlir::OwningRewritePatternList pattern(context);
     pattern.insert<
         AbsentOpConversion, AddcOpConversion, AddrOfOpConversion,
         AllocaOpConversion, BoxAddrOpConversion, BoxCharLenOpConversion,
         BoxDimsOpConversion, BoxEleSizeOpConversion, BoxIsAllocOpConversion,
         BoxIsArrayOpConversion, BoxIsPtrOpConversion, BoxRankOpConversion,
-        CallOpConversion, CmpcOpConversion, ConvertOpConversion,
-        DispatchOpConversion, DispatchTableOpConversion, DTEntryOpConversion,
-        DivcOpConversion, EmboxCharOpConversion, ExtractValueOpConversion,
-        HasValueOpConversion, GenTypeDescOpConversion, GlobalLenOpConversion,
-        GlobalOpConversion, InsertOnRangeOpConversion, InsertValueOpConversion,
-        IsPresentOpConversion, LoadOpConversion, NegcOpConversion,
-        MulcOpConversion, SelectCaseOpConversion, SelectOpConversion,
-        SelectRankOpConversion, SelectTypeOpConversion, StoreOpConversion,
-        StringLitOpConversion, SubcOpConversion, UnboxCharOpConversion,
-        UndefOpConversion, UnreachableOpConversion, ZeroOpConversion>(
-        typeConverter);
+        CallOpConversion, CmpcOpConversion, ConstcOpConversion,
+        ConvertOpConversion, DispatchOpConversion, DispatchTableOpConversion,
+        DTEntryOpConversion, DivcOpConversion, EmboxCharOpConversion,
+        ExtractValueOpConversion, HasValueOpConversion, GenTypeDescOpConversion,
+        GlobalLenOpConversion, GlobalOpConversion, InsertOnRangeOpConversion,
+        InsertValueOpConversion, IsPresentOpConversion, LoadOpConversion,
+        NegcOpConversion, MulcOpConversion, SelectCaseOpConversion,
+        SelectOpConversion, SelectRankOpConversion, SelectTypeOpConversion,
+        StoreOpConversion, StringLitOpConversion, 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

 // CHECK:         %[[CONVERTY:.*]] = llvm.fptrunc %[[Y]] : f128 to f16
 // CHECK:         %[[STRUCT0:.*]] = llvm.mlir.undef : !llvm.struct<(f16, f16)>
 // CHECK:         %[[STRUCT1:.*]] = llvm.insertvalue %[[CONVERTX]], %[[STRUCT0]][0 : i32] : !llvm.struct<(f16, f16)>
 // CHECK:         %[[STRUCT2:.*]] = llvm.insertvalue %[[CONVERTY]], %[[STRUCT1]][1 : i32] : !llvm.struct<(f16, f16)>
 // CHECK:         llvm.return %[[STRUCT2]] : !llvm.struct<(f16, f16)>
 
 // -----
 
+// Test constc.
+
+func @test_constc() -> !fir.complex<4> {
+  %0 = fir.constc (#fir.real<4, 1.4>, #fir.real<4, 2.3>) : !fir.complex<4>
+  return %0 : !fir.complex<4>
+}
+
+// CHECK-LABEL: @test_constc
+// CHECK_SAME: () -> !llvm.struct<(f32, f32)>
+// CHECK-DAG: [[rp:%.*]] = llvm.mlir.constant(1.400000e+00 : f32) : f32
+// CHECK-DAG: [[ip:%.*]] = llvm.mlir.constant(2.300000e+00 : f32) : f32
+// CHECK: [[undef:%.*]] = llvm.mlir.undef : !llvm.struct<(f32, f32)>
+// CHECK: [[withr:%.*]] = llvm.insertvalue [[rp]], [[undef]][0 : i32] : !llvm.struct<(f32, f32)>
+// CHECK: [[full:%.*]] = llvm.insertvalue [[ip]], [[withr]][1 : i32] : !llvm.struct<(f32, f32)>
+// CHECK: return [[full]] : !llvm.struct<(f32, f32)>
+
+// -----
+
 // Test `fir.store` --> `llvm.store` conversion
 
 func @test_store_index(%val_to_store : index, %addr : !fir.ref<index>) {
   fir.store %val_to_store to %addr : !fir.ref<index>
   return
 }
 
 // CHECK-LABEL:   llvm.func @test_store_index