[PATCH] D30088: [OpenMP] Remove barriers at cancel and cancellation point

Jonas Hahnfeld via Phabricator via cfe-commits Fri, 17 Feb 2017 04:09:07 -0800

Hahnfeld created this revision.

This resolves a deadlock with the cancel directive when there is no explicit
cancellation point. In that case, the implicit barrier acts as cancellation
point. After removing the barrier after cancel, the now unmatched barrier for
the explicit cancellation point has to go as well.


This has probably worked before https://reviews.llvm.org/rL255992: With the 
calls for the explicit
barrier, it was sure that all threads passed a barrier before exiting.

Reported by Simon Convent and Joachim Protze!


https://reviews.llvm.org/D30088

Files:
  lib/CodeGen/CGOpenMPRuntime.cpp
  test/OpenMP/cancel_codegen.cpp
  test/OpenMP/cancellation_point_codegen.cpp

Index: test/OpenMP/cancellation_point_codegen.cpp
===================================================================
--- test/OpenMP/cancellation_point_codegen.cpp
+++ test/OpenMP/cancellation_point_codegen.cpp
@@ -26,7 +26,6 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
@@ -46,15 +45,13 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
 // CHECK: [[RES:%.+]] = call i32 @__kmpc_cancellationpoint(%ident_t* {{[^,]+}}, i32 [[GTID]], i32 3)
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
@@ -69,7 +66,6 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
@@ -116,7 +112,6 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,]+]],
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label %[[RETURN:.+]]
 // CHECK: [[RETURN]]
 // CHECK: ret void
@@ -126,7 +121,6 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,]+]],
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label %[[RETURN:.+]]
 // CHECK: [[RETURN]]
 // CHECK: ret i32 0
@@ -137,7 +131,6 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
@@ -150,15 +143,13 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
 // CHECK: [[RES:%.+]] = call i32 @__kmpc_cancellationpoint(%ident_t* {{[^,]+}}, i32 [[GTID]], i32 3)
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
@@ -171,7 +162,6 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
Index: test/OpenMP/cancel_codegen.cpp
===================================================================
--- test/OpenMP/cancel_codegen.cpp
+++ test/OpenMP/cancel_codegen.cpp
@@ -12,15 +12,16 @@
 {
 #pragma omp cancel parallel if(flag)
   argv[0][0] = argc;
+#pragma omp barrier
+  argv[0][0] += argc;
 }
 // CHECK: call void (%ident_t*, i32, void (i32*, i32*, ...)*, ...) @__kmpc_fork_call(
 #pragma omp sections
 {
 #pragma omp cancel sections
 }
 // CHECK: call void @__kmpc_for_static_init_4(
 // CHECK: call i32 @__kmpc_cancel(
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: call void @__kmpc_for_static_fini(
 // CHECK: call void @__kmpc_barrier(%ident_t*
 #pragma omp sections
@@ -36,15 +37,13 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
 // CHECK: [[RES:%.+]] = call i32 @__kmpc_cancel(%ident_t* {{[^,]+}}, i32 [[GTID]], i32 3)
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
@@ -62,7 +61,6 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
@@ -109,9 +107,10 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,]+]],
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label %[[RETURN:.+]]
 // CHECK: [[ELSE]]
+// The barrier directive should now call __kmpc_cancel_barrier
+// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[RETURN]]
 // CHECK: ret void
@@ -121,15 +120,13 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,]+]],
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label %[[RETURN:.+]]
 // CHECK: [[RETURN]]
 // CHECK: ret i32 0
 
 // CHECK: define internal void @{{[^(]+}}(i32* {{[^,]+}}, i32* {{[^,]+}})
 // CHECK: call void @__kmpc_for_static_init_4(
 // CHECK: call i32 @__kmpc_cancel(
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: call void @__kmpc_for_static_fini(
 // CHECK: ret void
 
@@ -139,15 +136,13 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
 // CHECK: [[RES:%.+]] = call i32 @__kmpc_cancel(%ident_t* {{[^,]+}}, i32 [[GTID]], i32 3)
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
@@ -160,7 +155,6 @@
 // CHECK: [[CMP:%.+]] = icmp ne i32 [[RES]], 0
 // CHECK: br i1 [[CMP]], label %[[EXIT:[^,].+]], label %[[CONTINUE:.+]]
 // CHECK: [[EXIT]]
-// CHECK: call i32 @__kmpc_cancel_barrier(%ident_t*
 // CHECK: br label
 // CHECK: [[CONTINUE]]
 // CHECK: br label
Index: lib/CodeGen/CGOpenMPRuntime.cpp
===================================================================
--- lib/CodeGen/CGOpenMPRuntime.cpp
+++ lib/CodeGen/CGOpenMPRuntime.cpp
@@ -4721,16 +4721,13 @@
       auto *Result = CGF.EmitRuntimeCall(
           createRuntimeFunction(OMPRTL__kmpc_cancellationpoint), Args);
       // if (__kmpc_cancellationpoint()) {
-      //  __kmpc_cancel_barrier();
       //   exit from construct;
       // }
       auto *ExitBB = CGF.createBasicBlock(".cancel.exit");
       auto *ContBB = CGF.createBasicBlock(".cancel.continue");
       auto *Cmp = CGF.Builder.CreateIsNotNull(Result);
       CGF.Builder.CreateCondBr(Cmp, ExitBB, ContBB);
       CGF.EmitBlock(ExitBB);
-      // __kmpc_cancel_barrier();
-      emitBarrierCall(CGF, Loc, OMPD_unknown, /*EmitChecks=*/false);
       // exit from construct;
       auto CancelDest =
           CGF.getOMPCancelDestination(OMPRegionInfo->getDirectiveKind());
@@ -4759,16 +4756,13 @@
       auto *Result = CGF.EmitRuntimeCall(
           RT.createRuntimeFunction(OMPRTL__kmpc_cancel), Args);
       // if (__kmpc_cancel()) {
-      //  __kmpc_cancel_barrier();
       //   exit from construct;
       // }
       auto *ExitBB = CGF.createBasicBlock(".cancel.exit");
       auto *ContBB = CGF.createBasicBlock(".cancel.continue");
       auto *Cmp = CGF.Builder.CreateIsNotNull(Result);
       CGF.Builder.CreateCondBr(Cmp, ExitBB, ContBB);
       CGF.EmitBlock(ExitBB);
-      // __kmpc_cancel_barrier();
-      RT.emitBarrierCall(CGF, Loc, OMPD_unknown, /*EmitChecks=*/false);
       // exit from construct;
       auto CancelDest =
           CGF.getOMPCancelDestination(OMPRegionInfo->getDirectiveKind());

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[PATCH] D30088: [OpenMP] Remove barriers at cancel and cancellation point

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