From 44e5b4e533a92ff44ae57cf0129398b162e82bf6 Mon Sep 17 00:00:00 2001 From: "Duncan P. N. Exon Smith" Date: Tue, 21 Oct 2014 22:27:47 +0000 Subject: [PATCH] IR: Reorder metadata bitcode serialization, NFC Enumerate `MDNode`'s operands *before* the node itself, so that the reader requires less RAUW. Although this will cause different code paths to be hit in the reader, this should effectively be no functionality change. llvm-svn: 220340 --- llvm/lib/Bitcode/Writer/ValueEnumerator.cpp | 26 ++++++++++++++------------ 1 file changed, 14 insertions(+), 12 deletions(-) diff --git a/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp b/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp index f2be18e..c14591a 100644 --- a/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp +++ b/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp @@ -495,29 +495,31 @@ void ValueEnumerator::EnumerateMDNodeOperands(const MDNode *N) { void ValueEnumerator::EnumerateMetadata(const Value *MD) { assert((isa(MD) || isa(MD)) && "Invalid metadata kind"); - // Enumerate the type of this value. - EnumerateType(MD->getType()); - + // Skip function-local nodes themselves, but walk their operands. const MDNode *N = dyn_cast(MD); - - // In the module-level pass, skip function-local nodes themselves, but - // do walk their operands. if (N && N->isFunctionLocal() && N->getFunction()) { EnumerateMDNodeOperands(N); return; } - // Check to see if it's already in! - unsigned &MDValueID = MDValueMap[MD]; - if (MDValueID) + // Insert a dummy ID to block the co-recursive call to + // EnumerateMDNodeOperands() from re-visiting MD in a cyclic graph. + // + // Return early if there's already an ID. + if (!MDValueMap.insert(std::make_pair(MD, 0)).second) return; - MDValues.push_back(MD); - MDValueID = MDValues.size(); + // Enumerate the type of this value. + EnumerateType(MD->getType()); - // Enumerate all non-function-local operands. + // Visit operands first to minimize RAUW. if (N) EnumerateMDNodeOperands(N); + + // Replace the dummy ID inserted above with the correct one. MDValueMap may + // have changed by inserting operands, so we need a fresh lookup here. + MDValues.push_back(MD); + MDValueMap[MD] = MDValues.size(); } /// EnumerateFunctionLocalMetadataa - Incorporate function-local metadata -- 2.7.4