[flang][cuda] Run target rewrite in gpu.module (#118592)

Apply signature conversion for `func.func` in the gpu.module. More work
will need to be done for gpu.func op and implement the NVVM ABI for
conversion in the gpu module.

Author: clementval

flang/lib/Optimizer/CodeGen/TargetRewrite.cpp

@@ -27,6 +27,7 @@
 #include "flang/Optimizer/Dialect/Support/FIRContext.h"
 #include "flang/Optimizer/Support/DataLayout.h"
 #include "mlir/Dialect/DLTI/DLTI.h"
+#include "mlir/Dialect/GPU/IR/GPUDialect.h"
 #include "mlir/Dialect/LLVMIR/LLVMDialect.h"
 #include "mlir/Transforms/DialectConversion.h"
 #include "llvm/ADT/STLExtras.h"
@@ -720,6 +721,11 @@ class TargetRewrite : public fir::impl::TargetRewritePassBase<TargetRewrite> {
 
       convertSignature(fn);
     }
+
+    for (auto gpuMod : mod.getOps<mlir::gpu::GPUModuleOp>())
+      for (auto fn : gpuMod.getOps<mlir::func::FuncOp>())
+        convertSignature(fn);
+
     return mlir::success();
   }
 

flang/test/Fir/CUDA/cuda-target-rewrite.mlir

@@ -0,0 +1,16 @@
+// RUN: fir-opt --target-rewrite %s | FileCheck %s
+
+gpu.module @testmod {
+  gpu.func @_QPvcpowdk(%arg0: !fir.ref<complex<f64>> {cuf.data_attr = #cuf.cuda<device>, fir.bindc_name = "a"}) attributes {cuf.proc_attr = #cuf.cuda_proc<global>} {
+    %0 = fir.alloca i64
+    %1 = fir.load %0 : !fir.ref<i64>
+    %2 = fir.load %arg0 : !fir.ref<complex<f64>>
+    %3 = fir.call @_FortranAzpowk(%2, %1) fastmath<contract> : (complex<f64>, i64) -> complex<f64>
+    gpu.return
+  }
+  func.func private @_FortranAzpowk(complex<f64>, i64) -> complex<f64> attributes {fir.bindc_name = "_FortranAzpowk", fir.runtime}
+}
+
+// CHECK-LABEL: gpu.func @_QPvcpowdk
+// CHECK: %{{.*}} = fir.call @_FortranAzpowk(%{{.*}}, %{{.*}}, %{{.*}}) : (f64, f64, i64) -> tuple<f64, f64>
+// CHECK: func.func private @_FortranAzpowk(f64, f64, i64) -> tuple<f64, f64> attributes {fir.bindc_name = "_FortranAzpowk", fir.runtime}