[Mlir-commits] [mlir] c0fc5be - [Flang][OpenMP] Fix to resolve the crash with SIMD aligned clause. (#150612)
llvmlistbot at llvm.org
llvmlistbot at llvm.org
Thu Aug 28 23:18:28 PDT 2025
Author: Kaviya Rajendiran
Date: 2025-08-29T11:48:24+05:30
New Revision: c0fc5be60fd74babaf1a0b3dd3a44eeb9f3d73dc
URL: https://github.com/llvm/llvm-project/commit/c0fc5be60fd74babaf1a0b3dd3a44eeb9f3d73dc
DIFF: https://github.com/llvm/llvm-project/commit/c0fc5be60fd74babaf1a0b3dd3a44eeb9f3d73dc.diff
LOG: [Flang][OpenMP] Fix to resolve the crash with SIMD aligned clause. (#150612)
**Issue:**
When SIMD aligned clause has a alignment value which is not a power of
2, compiler crashes with error Assertion (alignment & (alignment - 1))
== 0 && "alignment is not power of 2"
**Fix:**
According to LLVM Language Reference manual
[[link]](https://llvm.org/docs/LangRef.html#assume-opbundles), the
alignment value may be non-power-of-two. In that case, the pointer value
must be a null pointer otherwise the behavior is undefined.
So instead of emitting `llvm.assume` intrinsic function with a null
pointer having the specified alignment, modified the implementation
which ignores the aligned clause which has an alignment value which is
not a power of 2. This patch also emits a warning indicating that the aligned clause is ignored if the alignment value is not a power of two.
It fixes the issue https://github.com/llvm/llvm-project/issues/149458
Added:
Modified:
flang/lib/Lower/OpenMP/ClauseProcessor.cpp
flang/lib/Semantics/check-omp-structure.cpp
flang/test/Lower/OpenMP/simd.f90
flang/test/Semantics/OpenMP/simd-aligned.f90
mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
mlir/test/Target/LLVMIR/openmp-simd-aligned.mlir
Removed:
################################################################################
diff --git a/flang/lib/Lower/OpenMP/ClauseProcessor.cpp b/flang/lib/Lower/OpenMP/ClauseProcessor.cpp
index bedcb2a267d92..6b9bd6640b393 100644
--- a/flang/lib/Lower/OpenMP/ClauseProcessor.cpp
+++ b/flang/lib/Lower/OpenMP/ClauseProcessor.cpp
@@ -648,10 +648,8 @@ addAlignedClause(lower::AbstractConverter &converter,
// The default alignment for some targets is equal to 0.
// Do not generate alignment assumption if alignment is less than or equal to
- // 0.
- if (alignment > 0) {
- // alignment value must be power of 2
- assert((alignment & (alignment - 1)) == 0 && "alignment is not power of 2");
+ // 0 or not a power of two
+ if (alignment > 0 && ((alignment & (alignment - 1)) == 0)) {
auto &objects = std::get<omp::ObjectList>(clause.t);
if (!objects.empty())
genObjectList(objects, converter, alignedVars);
diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index 7ca385792177a..742b58ce7e741 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -3489,9 +3489,14 @@ void OmpStructureChecker::Enter(const parser::OmpClause::Aligned &x) {
x.v, llvm::omp::OMPC_aligned, GetContext().clauseSource, context_)) {
auto &modifiers{OmpGetModifiers(x.v)};
if (auto *align{OmpGetUniqueModifier<parser::OmpAlignment>(modifiers)}) {
- if (const auto &v{GetIntValue(align->v)}; !v || *v <= 0) {
+ const auto &v{GetIntValue(align->v)};
+ if (!v || *v <= 0) {
context_.Say(OmpGetModifierSource(modifiers, align),
"The alignment value should be a constant positive integer"_err_en_US);
+ } else if (((*v) & (*v - 1)) != 0) {
+ context_.Warn(common::UsageWarning::OpenMPUsage,
+ OmpGetModifierSource(modifiers, align),
+ "Alignment is not a power of 2, Aligned clause will be ignored"_warn_en_US);
}
}
}
diff --git a/flang/test/Lower/OpenMP/simd.f90 b/flang/test/Lower/OpenMP/simd.f90
index d815474b84b31..7655c786573e3 100644
--- a/flang/test/Lower/OpenMP/simd.f90
+++ b/flang/test/Lower/OpenMP/simd.f90
@@ -226,6 +226,23 @@ subroutine simdloop_aligned_allocatable()
end do
end subroutine
+subroutine aligned_non_power_of_two()
+ integer :: i
+ integer, allocatable :: A(:)
+ allocate(A(10))
+!CHECK: %[[A_PTR:.*]] = fir.alloca !fir.box<!fir.heap<!fir.array<?xi32>>> {bindc_name = "a",
+!CHECK-SAME: uniq_name = "_QFaligned_non_power_of_twoEa"}
+!CHECK: %[[A_DECL:.*]]:2 = hlfir.declare %[[A_PTR]] {fortran_attrs = #fir.var_attrs<allocatable>,
+!CHECK-SAME: uniq_name = "_QFaligned_non_power_of_twoEa"} :
+!CHECK-SAME: (!fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>) ->
+!CHECK-SAME: (!fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>, !fir.ref<!fir.box<!fir.heap<!fir.array<?xi32>>>>)
+!CHECK: omp.simd private
+ !$OMP SIMD ALIGNED(A:257)
+ do i = 1, 10
+ A(i) = i
+ end do
+end subroutine
+
!CHECK-LABEL: func @_QPsimd_with_nontemporal_clause
subroutine simd_with_nontemporal_clause(n)
!CHECK: %[[A_DECL:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "_QFsimd_with_nontemporal_clauseEa"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
diff --git a/flang/test/Semantics/OpenMP/simd-aligned.f90 b/flang/test/Semantics/OpenMP/simd-aligned.f90
index 0a9f95833e22e..4c410a7c4631b 100644
--- a/flang/test/Semantics/OpenMP/simd-aligned.f90
+++ b/flang/test/Semantics/OpenMP/simd-aligned.f90
@@ -60,9 +60,16 @@ program omp_simd
!$omp end simd
!ERROR: 'd' in ALIGNED clause must be of type C_PTR, POINTER or ALLOCATABLE
+ !WARNING: Alignment is not a power of 2, Aligned clause will be ignored [-Wopen-mp-usage]
!$omp simd aligned(d:100)
do i = 1, 100
d(i) = i
end do
+ !WARNING: Alignment is not a power of 2, Aligned clause will be ignored [-Wopen-mp-usage]
+ !$omp simd aligned(b:65)
+ do i = 1, 100
+ b(i) = i
+ end do
+
end program omp_simd
diff --git a/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp b/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
index 6694de8383534..769065cef6f5c 100644
--- a/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
@@ -2893,6 +2893,12 @@ convertOmpSimd(Operation &opInst, llvm::IRBuilderBase &builder,
alignment = builder.getInt64(intAttr.getInt());
assert(ty->isPointerTy() && "Invalid type for aligned variable");
assert(alignment && "Invalid alignment value");
+
+ // Check if the alignment value is not a power of 2. If so, skip emitting
+ // alignment.
+ if (!intAttr.getValue().isPowerOf2())
+ continue;
+
auto curInsert = builder.saveIP();
builder.SetInsertPoint(sourceBlock);
llvmVal = builder.CreateLoad(ty, llvmVal);
diff --git a/mlir/test/Target/LLVMIR/openmp-simd-aligned.mlir b/mlir/test/Target/LLVMIR/openmp-simd-aligned.mlir
index 234604e4b664a..902548cb31d20 100644
--- a/mlir/test/Target/LLVMIR/openmp-simd-aligned.mlir
+++ b/mlir/test/Target/LLVMIR/openmp-simd-aligned.mlir
@@ -58,3 +58,25 @@ llvm.func @_QPsimd_aligned_allocatable() {
}
llvm.return
}
+
+//CHECK-LABEL: define void @_QPsimd_aligned_non_power_of_two() {
+//CHECK: %[[A_ADDR:.*]] = alloca { ptr, i64, i32, i8, i8, i8, i8, [1 x [3 x i64]] }, i64 1, align 8
+//CHECK: %[[B_ADDR:.*]] = alloca { ptr, i64, i32, i8, i8, i8, i8, [1 x [3 x i64]] }, i64 1, align 8
+//CHECK: %[[LOAD_B:.*]] = load ptr, ptr %[[B_ADDR]], align 8
+//CHECK: call void @llvm.assume(i1 true) [ "align"(ptr %[[LOAD_B]], i64 64) ]
+//CHECK-NOT: call void @llvm.assume(i1 true) [ "align"(ptr %{{.*}}, i64 257) ]
+llvm.func @_QPsimd_aligned_non_power_of_two() {
+ %0 = llvm.mlir.constant(1 : i64) : i64
+ %1 = llvm.alloca %0 x !llvm.struct<(ptr, i64, i32, i8, i8, i8, i8, array<1 x array<3 x i64>>)> {bindc_name = "a"} : (i64) -> !llvm.ptr
+ %2 = llvm.alloca %0 x !llvm.struct<(ptr, i64, i32, i8, i8, i8, i8, array<1 x array<3 x i64>>)> {bindc_name = "b"} : (i64) -> !llvm.ptr
+ %3 = llvm.mlir.constant(1 : i32) : i32
+ %4 = llvm.mlir.constant(10 : i32) : i32
+ %5 = llvm.mlir.constant(1 : i32) : i32
+ omp.simd aligned(%1 : !llvm.ptr -> 257 : i64, %2 : !llvm.ptr -> 64 : i64) {
+ omp.loop_nest (%arg0) : i32 = (%3) to (%4) inclusive step (%5) {
+ omp.yield
+ }
+ }
+ llvm.return
+}
+
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