[OpenACC][CIR] implement 'collapse' lowering for combined constructs

Another trivial implementation. It has a constant value that doesn't
require any insertion of instructions, so this just works with minimal
effort.

Author: erichkeane

clang/lib/CIR/CodeGen/CIRGenOpenACCClause.h

@@ -414,10 +414,10 @@ class OpenACCClauseCIREmitter final
       value = value.sextOrTrunc(64);
       operation.setCollapseForDeviceTypes(builder.getContext(),
                                           lastDeviceTypeValues, value);
+    } else if constexpr (isCombinedType<OpTy>) {
+      applyToLoopOp(clause);
     } else {
-      // TODO: When we've implemented this for everything, switch this to an
-      // unreachable. Combined constructs remain.
-      return clauseNotImplemented(clause);
+      llvm_unreachable("Unknown construct kind in VisitCollapseClause");
     }
   }
 

clang/test/CIR/CodeGenOpenACC/combined.cpp

@@ -134,4 +134,46 @@ extern "C" void acc_combined(int N) {
   // CHECK: acc.terminator
   // CHECK-NEXT: } loc
 
+  #pragma acc parallel loop collapse(1) device_type(radeon)
+  for(unsigned I = 0; I < N; ++I)
+    for(unsigned J = 0; J < N; ++J)
+      for(unsigned K = 0; K < N; ++K);
+  // CHECK: acc.parallel combined(loop) {
+  // CHECK: acc.loop combined(parallel) {
+  // CHECK: acc.yield
+  // CHECK-NEXT: } attributes {collapse = [1], collapseDeviceType = [#acc.device_type<none>]}
+  // CHECK: acc.yield
+  // CHECK-NEXT: } loc
+
+  #pragma acc serial loop collapse(1) device_type(radeon) collapse (2)
+  for(unsigned I = 0; I < N; ++I)
+    for(unsigned J = 0; J < N; ++J)
+      for(unsigned K = 0; K < N; ++K);
+  // CHECK: acc.serial combined(loop) {
+  // CHECK: acc.loop combined(serial) {
+  // CHECK: acc.yield
+  // CHECK-NEXT: } attributes {collapse = [1, 2], collapseDeviceType = [#acc.device_type<none>, #acc.device_type<radeon>]}
+  // CHECK: acc.yield
+  // CHECK-NEXT: } loc
+
+  #pragma acc kernels loop collapse(1) device_type(radeon, nvidia) collapse (2)
+  for(unsigned I = 0; I < N; ++I)
+    for(unsigned J = 0; J < N; ++J)
+      for(unsigned K = 0; K < N; ++K);
+  // CHECK: acc.kernels combined(loop) {
+  // CHECK: acc.loop combined(kernels) {
+  // CHECK: acc.yield
+  // CHECK-NEXT: } attributes {collapse = [1, 2, 2], collapseDeviceType = [#acc.device_type<none>, #acc.device_type<radeon>, #acc.device_type<nvidia>]}
+  // CHECK: acc.terminator
+  // CHECK-NEXT: } loc
+  #pragma acc parallel loop collapse(1) device_type(radeon, nvidia) collapse(2) device_type(host) collapse(3)
+  for(unsigned I = 0; I < N; ++I)
+    for(unsigned J = 0; J < N; ++J)
+      for(unsigned K = 0; K < N; ++K);
+  // CHECK: acc.parallel combined(loop) {
+  // CHECK: acc.loop combined(parallel) {
+  // CHECK: acc.yield
+  // CHECK-NEXT: } attributes {collapse = [1, 2, 2, 3], collapseDeviceType = [#acc.device_type<none>, #acc.device_type<radeon>, #acc.device_type<nvidia>, #acc.device_type<host>]}
+  // CHECK: acc.yield
+  // CHECK-NEXT: } loc
 }