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[OpenMP][Offload] Add support for lambdas with debug conditions #172107

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Merged
adurang merged 1 commit into from
Dec 16, 2025
+46 −9
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[OpenMP][Offload] Add support for lambdas with debug conditions #172107

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55 changes: 46 additions & 9 deletions offload/include/Shared/Debug.h
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Original file line number Diff line number Diff line change
Expand Up @@ -432,15 +432,22 @@ static inline raw_ostream &operator<<(raw_ostream &Os,

// helper templates to support lambdas with different number of arguments
template <typename LambdaTy> struct LambdaHelper {
template <typename T, typename = std::void_t<>>
struct has_two_args : std::false_type {};
template <typename T>
struct has_two_args<T,
std::void_t<decltype(std::declval<T>().operator()(1, 2))>>
: std::true_type {};
template <typename FuncTy, typename RetTy, typename... Args>
static constexpr size_t CountArgs(RetTy (FuncTy::*)(Args...)) {
return sizeof...(Args);
}
template <typename FuncTy, typename RetTy, typename... Args>
static constexpr size_t CountArgs(RetTy (FuncTy::*)(Args...) const) {
return sizeof...(Args);
}

static constexpr size_t NArgs = CountArgs(&LambdaTy::operator());
}
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@abhinavgaba abhinavgaba Dec 16, 2025

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There were some build issues that I saw locally. They may be environment specific, but to resolve them, I had to use the following patch:

diff --git a/offload/include/Shared/Debug.h b/offload/include/Shared/Debug.h
index 5cc98e16544d..7298b8597195 100644
--- a/offload/include/Shared/Debug.h
+++ b/offload/include/Shared/Debug.h
@@ -441,13 +441,12 @@ template <typename LambdaTy> struct LambdaHelper {
   static constexpr size_t CountArgs(RetTy (FuncTy::*)(Args...) const) {
     return sizeof...(Args);
   }
-
-  static constexpr size_t NArgs = CountArgs(&LambdaTy::operator());
-}
+};
 
 template <typename LambdaTy>
 struct LambdaOs : public LambdaHelper<LambdaTy> {
   static void dispatch(LambdaTy func, llvm::raw_ostream &Os, uint32_t Level) {
+    static constexpr size_t NArgs = LambdaHelper<LambdaTy>::CountArgs(&LambdaTy::operator());
     if constexpr (NArgs == 2)
       func(Os, Level);
     else
@@ -487,6 +486,7 @@ struct LambdaOs : public LambdaHelper<LambdaTy> {
 // helper templates to support lambdas with different number of arguments
 template <typename LambdaTy> struct LambdaIf : public LambdaHelper<LambdaTy> {
   static void dispatch(LambdaTy func, uint32_t Level) {
+    static constexpr size_t NArgs = LambdaHelper<LambdaTy>::CountArgs(&LambdaTy::operator());
     if constexpr (NArgs == 1)
       func(Level);
     else


template <typename LambdaTy>
struct LambdaOs : public LambdaHelper<LambdaTy> {
static void dispatch(LambdaTy func, llvm::raw_ostream &Os, uint32_t Level) {
if constexpr (has_two_args<LambdaTy>::value)
if constexpr (NArgs == 2)
func(Os, Level);
else
func(Os);
Expand All @@ -457,8 +464,8 @@ template <typename LambdaTy> struct LambdaHelper {
RealLevel, /*ShouldPrefixNextString=*/true, \
/*ShouldEmitNewLineOnDestruction=*/true}; \
auto F = Callback; \
::llvm::offload::debug::LambdaHelper<decltype(F)>::dispatch(F, OS, \
RealLevel); \
::llvm::offload::debug::LambdaOs<decltype(F)>::dispatch(F, OS, \
RealLevel); \
} \
}

Expand All @@ -476,6 +483,33 @@ template <typename LambdaTy> struct LambdaHelper {
#define ODBG_OS(...) \
ODBG_OS_SELECT(__VA_ARGS__ __VA_OPT__(, ) 3, 2, 1)(__VA_ARGS__)

// helper templates to support lambdas with different number of arguments
template <typename LambdaTy> struct LambdaIf : public LambdaHelper<LambdaTy> {
static void dispatch(LambdaTy func, uint32_t Level) {
if constexpr (NArgs == 1)
func(Level);
else
func();
}
};

#define ODBG_IF_BASE(Type, Level, Callback) \
if (::llvm::offload::debug::isDebugEnabled()) { \
uint32_t RealLevel = (Level); \
if (::llvm::offload::debug::shouldPrintDebug(GETNAME(TARGET_NAME), (Type), \
RealLevel)) { \
auto F = Callback; \
::llvm::offload::debug::LambdaIf<decltype(F)>::dispatch(F, RealLevel); \
} \
}

#define ODBG_IF_3(Type, Level, Callback) ODBG_IF_BASE(Type, Level, Callback)
#define ODBG_IF_2(Type, Callback) ODBG_IF_3(Type, 1, Callback)
#define ODBG_IF_1(Callback) ODBG_IF_2("default", Callback)
#define ODBG_IF_SELECT(Type, Level, Callback, NArgs, ...) ODBG_IF_##NArgs
#define ODBG_IF(...) \
ODBG_IF_SELECT(__VA_ARGS__ __VA_OPT__(, ) 3, 2, 1)(__VA_ARGS__)

#else

inline bool isDebugEnabled() { return false; }
Expand All @@ -496,6 +530,9 @@ inline bool isDebugEnabled() { return false; }
#define ODBG_OS_STREAM(Stream, Type, Level, Callback)
#define ODBG_OS(...)

#define ODBG_IF_BASE(Type, Level, Callback)
#define ODBG_IF(...)

#endif

} // namespace llvm::offload::debug
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