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[OpenMP] Add an option to always inline OpenMP device functions. 

Performance on GPU targets can be highly variable, sometimes inlining
everything hurts performance and sometimes it greatly improves it. Add
an option to toggle this behaviour to better investigate it.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D109014
This commit is contained in:
Joseph Huber 2021-08-31 15:03:33 -04:00
parent 862a311301
commit 29a74a3915
2 changed files with 81 additions and 0 deletions
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12
llvm/lib/Transforms/IPO/OpenMPOpt.cpp
View File

@ -97,6 +97,11 @@ static cl::opt<bool> PrintModuleAfterOptimizations(
cl::desc("Print the current module after OpenMP optimizations."),
cl::Hidden, cl::init(false));
static cl::opt<bool> AlwaysInlineDeviceFunctions(
"openmp-opt-inline-device", cl::ZeroOrMore,
cl::desc("Inline all applicible functions on the device."), cl::Hidden,
cl::init(false));
STATISTIC(NumOpenMPRuntimeCallsDeduplicated,
"Number of OpenMP runtime calls deduplicated");
STATISTIC(NumOpenMPParallelRegionsDeleted,
@ -4481,6 +4486,13 @@ PreservedAnalyses OpenMPOptPass::run(Module &M, ModuleAnalysisManager &AM) {
OpenMPOpt OMPOpt(SCC, CGUpdater, OREGetter, InfoCache, A);
bool Changed = OMPOpt.run(true);
// Optionally inline device functions for potentially better performance.
if (AlwaysInlineDeviceFunctions && isOpenMPDevice(M))
for (Function &F : M)
if (!F.isDeclaration() && !Kernels.contains(&F) &&
!F.hasFnAttribute(Attribute::NoInline))
F.addFnAttr(Attribute::AlwaysInline);
if (PrintModuleAfterOptimizations)
LLVM_DEBUG(dbgs() << TAG << "Module after OpenMPOpt Module Pass:\n" << M);

69
llvm/test/Transforms/OpenMP/always_inline_device.ll Normal file
View File

@ -0,0 +1,69 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-attributes
; RUN: opt < %s -S -passes=openmp-opt -openmp-opt-inline-device | FileCheck %s
%struct.ident_t = type { i32, i32, i32, i32, i8* }
@0 = private unnamed_addr constant [23 x i8] c";unknown;unknown;0;0;;\00", align 1
@1 = private unnamed_addr constant %struct.ident_t { i32 0, i32 2, i32 0, i32 0, i8* getelementptr inbounds ([23 x i8], [23 x i8]* @0, i32 0, i32 0) }, align 8
@__omp_offloading_fd02_c0934fc2_foo_l4_exec_mode = weak constant i8 1
@llvm.compiler.used = appending global [1 x i8*] [i8* @__omp_offloading_fd02_c0934fc2_foo_l4_exec_mode], section "llvm.metadata"
; Function Attrs: convergent norecurse nounwind
define weak void @__omp_offloading_fd02_c0934fc2_foo_l4() #0 {
; CHECK: Function Attrs: convergent norecurse nounwind
; CHECK-LABEL: @__omp_offloading_fd02_c0934fc2_foo_l4(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = call i32 @__kmpc_target_init(%struct.ident_t* @[[GLOB1:[0-9]+]], i1 true, i1 false, i1 false)
; CHECK-NEXT: [[EXEC_USER_CODE:%.*]] = icmp eq i32 [[TMP0]], -1
; CHECK-NEXT: br i1 [[EXEC_USER_CODE]], label [[USER_CODE_ENTRY:%.*]], label [[WORKER_EXIT:%.*]]
; CHECK: user_code.entry:
; CHECK-NEXT: call void @__kmpc_target_deinit(%struct.ident_t* @[[GLOB1]], i1 true, i1 false)
; CHECK-NEXT: ret void
; CHECK: worker.exit:
; CHECK-NEXT: ret void
;
entry:
%0 = call i32 @__kmpc_target_init(%struct.ident_t* @1, i1 false, i1 true, i1 true)
%exec_user_code = icmp eq i32 %0, -1
br i1 %exec_user_code, label %user_code.entry, label %worker.exit
user_code.entry: ; preds = %entry
call void @bar() #2
call void @__kmpc_target_deinit(%struct.ident_t* @1, i1 false, i1 true)
ret void
worker.exit: ; preds = %entry
ret void
}
declare i32 @__kmpc_target_init(%struct.ident_t*, i1, i1, i1)
declare void @__kmpc_target_deinit(%struct.ident_t*, i1, i1)
; Function Attrs: convergent nounwind
define hidden void @bar() #1 {
; CHECK: Function Attrs: alwaysinline convergent nounwind
; CHECK-LABEL: @bar(
; CHECK-NEXT: entry:
; CHECK-NEXT: ret void
;
entry:
ret void
}
attributes #0 = { convergent norecurse nounwind "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="sm_70" "target-features"="+ptx32,+sm_70" }
attributes #1 = { convergent nounwind "frame-pointer"="all" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="sm_70" "target-features"="+ptx32,+sm_70" }
attributes #2 = { convergent }
!omp_offload.info = !{!0}
!nvvm.annotations = !{!1}
!llvm.module.flags = !{!2, !3, !4, !5, !6}
!llvm.ident = !{!7}
!0 = !{i32 0, i32 64770, i32 -1064087614, !"foo", i32 4, i32 0}
!1 = !{void ()* @__omp_offloading_fd02_c0934fc2_foo_l4, !"kernel", i32 1}
!2 = !{i32 1, !"wchar_size", i32 4}
!3 = !{i32 7, !"openmp", i32 50}
!4 = !{i32 7, !"openmp-device", i32 50}
!5 = !{i32 7, !"PIC Level", i32 2}
!6 = !{i32 7, !"frame-pointer", i32 2}
!7 = !{!"clang version 14.0.0"}