[clang][OpenMP] Fix runtime crash in the call to __kmp_alloc.

[jyu2]

Summary

The problem is that "alloctor" from omp_init_allocator gets truncated before passing to __kmp_alloc.

To fix this, convert int type to UnsignedPointerDiffType to avoid truncate

[jyu2]

Ping!

[ABataev]

Why does it get truncated if the type must be integer? Probably, something incorrect in sema.

[jyu2]

In D129872#3671847, @ABataev wrote:

Why does it get truncated if the type must be integer? Probably, something incorrect in sema.

This is only failed with C. But not for C++. So I don't think we have problem for Seam. I may missing something...
The different is in reprehensive of enum type between c vs c++:
For C:

-EnumDecl 0x1193f838 <line:18:9, line:33:1> line:18:14 omp_allocator_handle_t
	-EnumConstantDecl 0x1193f940 <line:19:3, col:24> col:3 referenced omp_null_allocator 'int'
	`-ConstantExpr 0x1193f920 <col:24> 'int'
		-value: Int 0
	`-IntegerLiteral 0x1193f900 <col:24> 'int' 0
	-EnumConstantDecl 0x1193f9d0 <line:20:7, col:31> col:7 referenced omp_default_mem_alloc 'int'
	`-ConstantExpr 0x1193f9b0 <col:31> 'int'
		-value: Int 1
	`-IntegerLiteral 0x1193f990 <col:31> 'int' 1

for C++:

-EnumDecl 0x11b31d88 <line:18:9, line:33:1> line:18:14 omp_allocator_handle_t
	-EnumConstantDecl 0x11b31e90 <line:19:3, col:24> col:3 referenced omp_null_allocator 'omp_allocator_handle_t'
	`-ImplicitCastExpr 0x11b4b770 <col:24> 'unsigned long' <IntegralCast>
	`-ConstantExpr 0x11b31e70 <col:24> 'int'
		-value: Int 0
	`-IntegerLiteral 0x11b31e50 <col:24> 'int' 0
	-EnumConstantDecl 0x11b31f20 <line:20:7, col:31> col:7 referenced omp_default_mem_alloc 'omp_allocator_handle_t'
	`-ImplicitCastExpr 0x11b4b788 <col:31> 'unsigned long' <IntegralCast>
	`-ConstantExpr 0x11b31f00 <col:31> 'int'
		-value: Int 1
	`-IntegerLiteral 0x11b31ee0 <col:31> 'int' 1

[ABataev]

In D129872#3672332, @jyu2 wrote:

In D129872#3671847, @ABataev wrote:

Why does it get truncated if the type must be integer? Probably, something incorrect in sema.

This is only failed with C. But not for C++. So I don't think we have problem for Seam. I may missing something...
The different is in reprehensive of enum type between c vs c++:
For C:

-EnumDecl 0x1193f838 <line:18:9, line:33:1> line:18:14 omp_allocator_handle_t
	-EnumConstantDecl 0x1193f940 <line:19:3, col:24> col:3 referenced omp_null_allocator 'int'
	`-ConstantExpr 0x1193f920 <col:24> 'int'
		-value: Int 0
	`-IntegerLiteral 0x1193f900 <col:24> 'int' 0
	-EnumConstantDecl 0x1193f9d0 <line:20:7, col:31> col:7 referenced omp_default_mem_alloc 'int'
	`-ConstantExpr 0x1193f9b0 <col:31> 'int'
		-value: Int 1
	`-IntegerLiteral 0x1193f990 <col:31> 'int' 1

for C++:

-EnumDecl 0x11b31d88 <line:18:9, line:33:1> line:18:14 omp_allocator_handle_t
	-EnumConstantDecl 0x11b31e90 <line:19:3, col:24> col:3 referenced omp_null_allocator 'omp_allocator_handle_t'
	`-ImplicitCastExpr 0x11b4b770 <col:24> 'unsigned long' <IntegralCast>
	`-ConstantExpr 0x11b31e70 <col:24> 'int'
		-value: Int 0
	`-IntegerLiteral 0x11b31e50 <col:24> 'int' 0
	-EnumConstantDecl 0x11b31f20 <line:20:7, col:31> col:7 referenced omp_default_mem_alloc 'omp_allocator_handle_t'
	`-ImplicitCastExpr 0x11b4b788 <col:31> 'unsigned long' <IntegralCast>
	`-ConstantExpr 0x11b31f00 <col:31> 'int'
		-value: Int 1
	`-IntegerLiteral 0x11b31ee0 <col:31> 'int' 1

If the type does not match, we have a problem with casting. Need to add an explicit cast to int-like type rather than avoid implicit casts.

[ABataev]

clang/lib/Sema/SemaOpenMP.cpp

16379

It must be int type, no?

[jyu2]

clang/lib/Sema/SemaOpenMP.cpp

16379

unsigned int?

[ABataev]

clang/lib/Sema/SemaOpenMP.cpp

16379

Check the standard, IIRC it says just int.

[jyu2]

clang/lib/Sema/SemaOpenMP.cpp

16379

I see that is enum type.

Runtime library definitions: The enum types for omp_allocator_handle_t:

The type omp_allocator_handle_t, which must be an implementation-defined (for C++
possibly scoped) enum type with at least the omp_null_allocator enumerator with the
value zero and an enumerator for each predefined memory allocator in Table 2.10;

[ABataev]

clang/lib/Sema/SemaOpenMP.cpp

16379

IIRC, in C enums are always int-based.

[jyu2]

clang/lib/Sema/SemaOpenMP.cpp

16379

That is right. But not for C++.

[ABataev]

clang/lib/Sema/SemaOpenMP.cpp

16379

For C++ need to get the base int type.

[jyu2]

clang/lib/Sema/SemaOpenMP.cpp

16379

For C++ enum type is unsigned int:
since following is defined inside the omp_allocator_handle_t.
KMP_ALLOCATOR_MAX_HANDLE = (18446744073709551615UL)

But for C it is int.

-EnumDecl 0x11b31d88 <line:18:9, line:33:1> line:18:14 omp_allocator_handle_t
| |-EnumConstantDecl 0x11b31e90 <line:19:3, col:24> col:3 referenced omp_null_allocator 'omp_allocator_handle_t'
| | `-ImplicitCastExpr 0x11b4b770 <col:24> 'unsigned long' <IntegralCast>
| |   `-ConstantExpr 0x11b31e70 <col:24> 'int'
| |     |-value: Int 0

[ABataev]

clang/lib/Sema/SemaOpenMP.cpp

16379

I wouldn't rely on this, this is just implementation specific. Instead, need to find corresponding EnumDwcl and extract underlying integer type (getIntegerType). If it is null - the underlying type is int, otherwise use returned type.

clang/lib/Sema/SemaOpenMP.cpp

OMPClause *Sema::ActOnOpenMPAllocatorClause(Expr *A, SourceLocation StartLoc,
   // OpenMP [2.11.3, allocate Directive, Description]
   // allocator is an expression of omp_allocator_handle_t type.
   if (!findOMPAllocatorHandleT(*this, A->getExprLoc(), DSAStack))
     return nullptr;
 
   ExprResult Allocator = DefaultLvalueConversion(A);
   if (Allocator.isInvalid())
     return nullptr;
-  Allocator = PerformImplicitConversion(Allocator.get(),
-                                        DSAStack->getOMPAllocatorHandleT(),
+  QualType AllocatorHT = DSAStack->getOMPAllocatorHandleT();
+  if (!AllocatorHT->isEnumeralType() && AllocatorHT->isIntegerType())
+    // allocator_handler_t is enum type.  For int type convert to
+    // UnsignedPointerDiffType avoid truncate.
+    AllocatorHT = Context.getUnsignedPointerDiffType();
+  Allocator = PerformImplicitConversion(Allocator.get(), AllocatorHT,
                                         Sema::AA_Initializing,
                                         /*AllowExplicit=*/true);
   if (Allocator.isInvalid())
     return nullptr;
   return new (Context)
       OMPAllocatorClause(Allocator.get(), StartLoc, LParenLoc, EndLoc);
 }
 

clang/test/OpenMP/omp_init_allocator.c

+// RUN: %clang_cc1 -isystem %S/Inputs -emit-llvm -o - -fopenmp \
+// RUN: -fopenmp-version=50 -triple x86_64-unknown-linux-gnu %s | FileCheck %s
+
+typedef enum {
+  omp_atk_sync_hint = 1,
+  omp_atk_alignment = 2
+} omp_alloctrait_key_t;
+typedef unsigned long int uintptr_t;
+typedef uintptr_t omp_uintptr_t;
+typedef struct {
+  omp_alloctrait_key_t key;
+  omp_uintptr_t value;
+} omp_alloctrait_t;
+typedef enum omp_allocator_handle_t {
+  omp_null_allocator = 0,
+  omp_default_mem_alloc = 1,
+  omp_large_cap_mem_alloc = 2,
+  omp_const_mem_alloc = 3,
+  omp_high_bw_mem_alloc = 4,
+  omp_low_lat_mem_alloc = 5,
+  omp_cgroup_mem_alloc = 6,
+  omp_pteam_mem_alloc = 7,
+  omp_thread_mem_alloc = 8,
+
+  omp_target_host_mem_alloc = 100,
+  omp_target_shared_mem_alloc = 101,
+  omp_target_device_mem_alloc = 102,
+  KMP_ALLOCATOR_MAX_HANDLE = (18446744073709551615UL)
+} omp_allocator_handle_t;
+typedef enum omp_memspace_handle_t {
+  omp_default_mem_space = 0,
+  omp_large_cap_mem_space = 1,
+  omp_const_mem_space = 2,
+  omp_high_bw_mem_space = 3,
+  omp_low_lat_mem_space = 4,
+
+  omp_target_host_mem_space = 100,
+  omp_target_shared_mem_space = 101,
+  omp_target_device_mem_space = 102,
+  KMP_MEMSPACE_MAX_HANDLE = (18446744073709551615UL)
+} omp_memspace_handle_t;
+
+extern omp_allocator_handle_t omp_init_allocator(omp_memspace_handle_t m,
+                                                 int ntraits,
+                                                 omp_alloctrait_t traits[]);
+//CHECK-LABEL: test_allocate_allocator
+void test_allocate_allocator() {
+  omp_alloctrait_t x_traits[1] = {{omp_atk_alignment, 64}};
+  omp_allocator_handle_t x_alloc =
+      omp_init_allocator(omp_default_mem_space, 1, x_traits);
+  {
+    int x;
+// CHECK: [[RET:%.+]] = call i64 @omp_init_allocator
+// CHECK-NEXT: store i64 [[RET]], ptr [[X_ALLOC:%x_alloc]]
+// CHECK: [[TMP:%.+]] = load i64, ptr [[X_ALLOC]]
+// CHECK-NEXT: [[CONV:%conv]] = inttoptr i64 [[TMP]] to ptr
+// CHECK-NEXT: call ptr @__kmpc_alloc(i32 %0, i64 4, ptr [[CONV]])
+// CHECK-NOT: trunc
+#pragma omp allocate(x) allocator(x_alloc)
+  }
+}

openmp/runtime/test/api/omp_init_allocator.c

+// RUN: %libomp-compile-and-run
+
+#include <omp.h>
+#include <stdio.h>
+
+void test_allocate_allocator() {
+  omp_alloctrait_t x_traits[1] = {{omp_atk_alignment, 64}};
+  omp_allocator_handle_t x_alloc =
+      omp_init_allocator(omp_default_mem_space, 1, x_traits);
+  {
+    int x;
+#pragma omp allocate(x) allocator(x_alloc)
+  }
+  omp_destroy_allocator(x_alloc);
+}
+
+int main() {
+  test_allocate_allocator();
+  printf("passed\n");
+}