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abidhabidh
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[flang][OMPIRBuilder] Improve debug info for AMDGPU target.
This PR builds on PR#118314 and PR#125692 which enable the debugging of variables in the OpenMP target region. This PR adds the following changes so that usable debug info comes out of amdgpu backend. 1. Add DIOp based expressions. 2. Use alloca as location of the variable in debug record. Regarding 2nd point, OMPIRBuilder creates a function to implement target construct. The variable that are mapped are passed as argument to it. The argument handling code adds alloca+store+load for the arguments which are mapped by reference. It was observed that if the argument* is used as location of variable in debug record (directly or when it is result of LoadInst), the debug information is dropped for that variable. Thing work ok if the location of the alloca is used instead.
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‎flang/test/Integration/amdgpu/debug-target-var.f90

Lines changed: 24 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,24 @@
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! RUN: %flang_fc1 -triple amdgcn-amd-amdhsa -emit-llvm -fopenmp -fopenmp-is-target-device -debug-info-kind=standalone %s -o - | FileCheck %s
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subroutine fff(x, y)
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implicit none
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integer :: y(:)
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integer :: x
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!$omp target map(tofrom: x) map(tofrom: y)
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x = 5
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y = 10
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!$omp end target
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end subroutine fff
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!CHECK: define{{.*}}amdgpu_kernel void @[[FN:[0-9a-zA_Z_]+]]({{.*}}){{.*}}!dbg ![[SP:[0-9]+]]
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!CHECK: #dbg_declare({{.*}}, ![[X:[0-9]+]], !DIExpression(DIOpArg(0, ptr addrspace(5)), DIOpDeref(ptr), DIOpDeref(ptr)), {{.*}})
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!CHECK: #dbg_declare({{.*}}, ![[Y:[0-9]+]], !DIExpression(DIOpArg(0, ptr addrspace(5)), DIOpDeref(ptr), DIOpDeref(ptr)), {{.*}})
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!CHECK: }
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! CHECK-DAG: ![[SP]] = {{.*}}!DISubprogram(name: "[[FN]]"{{.*}})
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! CHECK-DAG: ![[X]] = !DILocalVariable(name: "x", arg: 2, scope: ![[SP]]{{.*}}type: ![[INT:[0-9]+]])
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! CHECK-DAG: ![[INT]] = !DIBasicType(name: "integer", size: 32, encoding: DW_ATE_signed)
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! CHECK-DAG: ![[Y]] = !DILocalVariable(name: "y", arg: 3, scope: ![[SP]]{{.*}}type: ![[ARR:[0-9]+]])
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! CHECK-DAG: ![[ARR]] = !DICompositeType(tag: DW_TAG_array_type, baseType: ![[INT]]{{.*}})

‎llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp

Lines changed: 49 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -6994,7 +6994,6 @@ static void FixupDebugInfoForOutlinedFunction(
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SmallDenseMap<DILocalVariable *, DILocalVariable *> RemappedVariables;
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auto GetUpdatedDIVariable = [&](DILocalVariable *OldVar, unsigned arg) {
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auto NewSP = Func->getSubprogram();
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DILocalVariable *&NewVar = RemappedVariables[OldVar];
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// Only use cached variable if the arg number matches. This is important
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// so that DIVariable created for privatized variables are not discarded.
@@ -7006,8 +7005,8 @@ static void FixupDebugInfoForOutlinedFunction(
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NewVar = llvm::DILocalVariable::get(
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Builder.getContext(), NewScope, OldVar->getName(), OldVar->getFile(),
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OldVar->getLine(), OldVar->getType(), arg, OldVar->getFlags(),
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llvm::dwarf::DW_MSPACE_LLVM_none,
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OldVar->getAlignInBits(), OldVar->getAnnotations());
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OldVar->getDWARFMemorySpace(), OldVar->getAlignInBits(),
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OldVar->getAnnotations());
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return NewVar;
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};
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@@ -7021,6 +7020,53 @@ static void FixupDebugInfoForOutlinedFunction(
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ArgNo = std::get<1>(Iter->second) + 1;
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}
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}
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Module *M = Func->getParent();
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if ((Triple(M->getTargetTriple())).isAMDGPU()) {
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// For target side, the ArgAccessorFuncCB/createDeviceArgumentAccessor
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// adds following for the kenel arguments.
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// %3 = alloca ptr, align 8, addrspace(5), !dbg !26
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// %4 = addrspacecast ptr addrspace(5) %3 to ptr, !dbg !26
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// store ptr %1, ptr %4, align 8, !dbg !26
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// For arguments that are passed by ref, there is an extra load like the
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// following.
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// %8 = load ptr, ptr %4, align 8
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//
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// The debug record at this moment may be pointing to %8 (in above
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// snippet) as location of variable. The AMDGPU backend drops the debug
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// info for variable in such cases. So we change the location to alloca
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// instead.
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bool passByRef = false;
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llvm::Type *locType = nullptr;
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for (auto Loc : DR->location_ops()) {
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locType = Loc->getType();
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if (llvm::LoadInst *Load = dyn_cast<llvm::LoadInst>(Loc)) {
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DR->replaceVariableLocationOp(Loc, Load->getPointerOperand());
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passByRef = true;
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}
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}
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// Add DIOps based expression. Note that we generate an extra indirection
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// if an argument is mapped by reference. The first reads the pointer
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// from alloca and 2nd read the value of the variable from that pointer.
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llvm::DIExprBuilder ExprBuilder(Builder.getContext());
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unsigned int allocaAS = M->getDataLayout().getAllocaAddrSpace();
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unsigned int defaultAS = M->getDataLayout().getProgramAddressSpace();
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ExprBuilder.append<llvm::DIOp::Arg>(0u, Builder.getPtrTy(allocaAS));
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// We have 2 options for the variables that are mapped byRef.
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// 1. Use a single indirection but change the type to the reference to the
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// original type. It will show up in the debugger as
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// "x=@0x7ffeec820000: 5"
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// This is similar to what clang does.
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// 2. Use double indirection and keep the original type. It will show up
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// in debugger as "x=5". This approached is used here as it is
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// consisten with the normal fortran parameters display.
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if (passByRef)
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ExprBuilder.append<llvm::DIOp::Deref>(Builder.getPtrTy(defaultAS));
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ExprBuilder.append<llvm::DIOp::Deref>(locType);
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DR->setExpression(ExprBuilder.intoExpression());
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}
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DR->setVariable(GetUpdatedDIVariable(OldVar, ArgNo));
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};
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‎mlir/test/Target/LLVMIR/omptarget-debug-var-1.mlir

Lines changed: 21 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -26,7 +26,7 @@
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#var_x = #llvm.di_local_variable<scope = #sp,
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name = "x", file = #file, line = 12, type = #real_ty>
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module attributes {llvm.target_triple = "amdgcn-amd-amdhsa", omp.is_target_device = true} {
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module attributes {llvm.target_triple = "amdgcn-amd-amdhsa", omp.is_target_device = true, dlti.dl_spec = #dlti.dl_spec<"dlti.alloca_memory_space" = 5 : ui64>} {
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llvm.func @test() {
3131
%0 = llvm.mlir.constant(1 : i64) : i64
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%1 = llvm.alloca %0 x f32 : (i64) -> !llvm.ptr
@@ -56,8 +56,23 @@ module attributes {llvm.target_triple = "amdgcn-amd-amdhsa", omp.is_target_devic
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#loc3 = loc(fused<#sp>[#loc2])
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#loc4 = loc(fused<#g_var>[#loc1])
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59-
// CHECK: ![[SP:[0-9]+]] = distinct !DISubprogram(name: "__omp_offloading{{.*}}test{{.*}})
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// CHECK: !DILocalVariable(name: "dyn_ptr", arg: 1, scope: ![[SP]]{{.*}}flags: DIFlagArtificial)
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// CHECK: !DILocalVariable(name: "x", arg: 2, scope: ![[SP]]{{.*}})
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// CHECK: !DILocalVariable(name: "arr", arg: 3, scope: ![[SP]]{{.*}})
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// CHECK: !DILocalVariable(name: "i", arg: 4, scope: ![[SP]]{{.*}})
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// CHECK: define{{.*}}@__omp_offloading{{.*}}test{{.*}}(ptr %0, ptr %[[ARG1:[0-9]+]], ptr %[[ARG2:[0-9]+]], ptr %[[ARG3:[0-9]+]])
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// CHECK-DAG: store ptr %[[ARG1]], ptr %[[CAST1:[0-9]+]]{{.*}}
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// CHECK-DAG: %[[CAST1]] = addrspacecast ptr addrspace(5) %[[AL1:[0-9]+]]
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// CHECK-DAG: %[[AL1]] = alloca{{.*}}
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// CHECK-DAG: store ptr %[[ARG2]], ptr %[[CAST2:[0-9]+]]{{.*}}
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// CHECK-DAG: %[[CAST2]] = addrspacecast ptr addrspace(5) %[[AL2:[0-9]+]]
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// CHECK-DAG: %[[AL2]] = alloca{{.*}}
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// CHECK-DAG: store ptr %[[ARG3]], ptr %[[CAST3:[0-9]+]]{{.*}}
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// CHECK-DAG: %[[CAST3]] = addrspacecast ptr addrspace(5) %[[AL3:[0-9]+]]
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// CHECK-DAG: %[[AL3]] = alloca{{.*}}
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// CHECK-DAG: #dbg_declare(ptr %[[CAST1]], ![[X:[0-9]+]], !DIExpression(DIOpArg(0, ptr addrspace(5)), DIOpDeref(ptr), DIOpDeref(ptr)), {{.*}})
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// CHECK-DAG: #dbg_declare(ptr %[[CAST2]], ![[ARR:[0-9]+]], !DIExpression(DIOpArg(0, ptr addrspace(5)), DIOpDeref(ptr), DIOpDeref(ptr)), {{.*}})
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// CHECK-DAG: #dbg_declare(ptr %[[CAST3]], ![[I:[0-9]+]], !DIExpression(DIOpArg(0, ptr addrspace(5)), DIOpDeref(ptr)), {{.*}})
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// CHECK-DAG: ![[SP:[0-9]+]] = distinct !DISubprogram(name: "__omp_offloading{{.*}}test{{.*}})
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// CHECK-DAG: !DILocalVariable(name: "dyn_ptr", arg: 1, scope: ![[SP]]{{.*}}flags: DIFlagArtificial)
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// CHECK-DAG: ![[X:[0-9]+]] = !DILocalVariable(name: "x", arg: 2, scope: ![[SP]]{{.*}})
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// CHECK-DAG: ![[ARR:[0-9]+]] = !DILocalVariable(name: "arr", arg: 3, scope: ![[SP]]{{.*}})
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// CHECK-DAG: ![[I:[0-9]+]] = !DILocalVariable(name: "i", arg: 4, scope: ![[SP]]{{.*}})

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