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[NVPTX] Add more clear error message for using invalid syncscope #165737

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[NVPTX] Add more clear error message for using invalid syncscope #165737

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30b99de
[NVPTX] Add more clear error message for using invalid syncscope
smada3 Oct 30, 2025
24ffd3e
Fixed printing code to be cleaner
smada3 Oct 31, 2025
294b0c1
Merge remote-tracking branch 'llvm/main' into github/smada/nvptx-syns…
smada3 Oct 31, 2025
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23 changes: 17 additions & 6 deletions llvm/lib/Target/NVPTX/NVPTXISelDAGToDAG.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1836,7 +1836,7 @@ bool NVPTXDAGToDAGISel::tryFence(SDNode *N) {
return true;
}

NVPTXScopes::NVPTXScopes(LLVMContext &C) {
NVPTXScopes::NVPTXScopes(LLVMContext &C) : Context(&C) {
Scopes[C.getOrInsertSyncScopeID("singlethread")] = NVPTX::Scope::Thread;
Scopes[C.getOrInsertSyncScopeID("")] = NVPTX::Scope::System;
Scopes[C.getOrInsertSyncScopeID("block")] = NVPTX::Scope::Block;
Expand All @@ -1851,11 +1851,22 @@ NVPTX::Scope NVPTXScopes::operator[](SyncScope::ID ID) const {

auto S = Scopes.find(ID);
if (S == Scopes.end()) {
// TODO:
// - Add API to LLVMContext to get the name of a single scope.
// - Use that API here to print an error containing the name
// of this Unknown ID.
report_fatal_error(formatv("Could not find scope ID={}.", int(ID)));
// Get the actual scope name from LLVMContext for a better error message
std::string scopeName = "<unknown>";
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Is this expected to ever happen? If so, please add a test, if not perhaps change to an assert?

if (auto name = Context->getSyncScopeName(ID))
scopeName = name->str();

// Build list of supported syncscopes programmatically
SmallVector<StringRef> supportedScopes;
for (const auto &Entry : Scopes) {
if (auto name = Context->getSyncScopeName(Entry.first))
supportedScopes.push_back(name->empty() ? "<empty string>" : *name);
}
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The error-reporting enhancement LGTM.

Would collecting the scopes in a small-vector and then using llvm::join (with comma as separator) make it simpler?

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Agreed, better yet use StringRefs as well and just comma join the list as part of formatv https://llvm.org/docs/ProgrammersManual.html#formatv-examples

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Nice, didn't know llvm:join existed. Changed to use both, take a look when you get a chance.

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You don't even need to use join in this case, just use the existing formatv support for ranges


reportFatalUsageError(
formatv("NVPTX backend does not support syncscope \"{0}\" (ID={1}).\n"
"Supported syncscopes are: {2}.",
scopeName, int(ID), llvm::join(supportedScopes, ", ")));
}
return S->second;
}
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1 change: 1 addition & 0 deletions llvm/lib/Target/NVPTX/NVPTXISelDAGToDAG.h
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Expand Up @@ -35,6 +35,7 @@ struct NVPTXScopes {

private:
SmallMapVector<SyncScope::ID, NVPTX::Scope, 8> Scopes{};
LLVMContext *Context = nullptr;
};

class LLVM_LIBRARY_VISIBILITY NVPTXDAGToDAGISel : public SelectionDAGISel {
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11 changes: 11 additions & 0 deletions llvm/test/CodeGen/NVPTX/cmpxchg-unsupported-syncscope.err.ll
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@@ -0,0 +1,11 @@
; RUN: not llc -mcpu=sm_100a -mtriple=nvptx64 -mattr=+ptx86 %s 2>&1 | FileCheck %s

; Test that we get a clear error message when using an unsupported syncscope.

; CHECK: NVPTX backend does not support syncscope "agent"
; CHECK: Supported syncscopes are: singlethread, <empty string>, block, cluster, device
define i32 @cmpxchg_unsupported_syncscope_agent(ptr %addr, i32 %cmp, i32 %new) {
%result = cmpxchg ptr %addr, i32 %cmp, i32 %new syncscope("agent") monotonic monotonic
%value = extractvalue { i32, i1 } %result, 0
ret i32 %value
}