[llvm][mustache] Avoid extra allocations in parseSection

[ilovepi]

We don't need to have extra allocations when concatenating raw bodies.

[ilovepi]

• [llvm][mustache] Avoid extra allocations in parseSection #159199 👈 (View in Graphite)
• [llvm][mustache] Optimize accessor splitting with a single pass #159198
• [llvm][mustache] Avoid redundant saves in accessor splitting #159197
• [llvm][mustache] Use single pass when tokenizing #159196
• [llvm][mustache] Avoid extra copy for json strings #159195
• [llvm][mustache] Use BumpPtrAllocator to save ASTNodes #159194
• [llvm][mustache] Simplify debug logging #159193
• [llvm][mustache] Fix failing StandaloneIndentation test #159192
• [llvm][mustache] Introduce MustacheContext to simplify mustache APIs #159191
• [llvm][mustache] Remove out parameters from processTags() #159190
• [llvm][mustache] Refactor template rendering #159189
• [llvm][mustache] Refactor tokenizer for clarity #159188
• [llvm][mustache] Support setting delimiters in templates #159187
• [llvm][mustache] Precommit test for Set Delimiter #159186
• [llvm][mustache] Align standalone partial indentation with spec #159185
• [llvm][mustache] Precommit test for StandaloneIndentation #159184
• [llvm][mustache] Add support for Triple Mustache #159183
• [llvm][mustache] Precommit tests for Triple Mustache #159182
• main

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[llvmbot]

@llvm/pr-subscribers-llvm-support

Author: Paul Kirth (ilovepi)

Changes

We don't need to have extra allocations when concatenating raw bodies.

---

Full diff: https://github.com/llvm/llvm-project/pull/159199.diff

1 Files Affected:

• (modified) llvm/lib/Support/Mustache.cpp (+8-1)

diff --git a/llvm/lib/Support/Mustache.cpp b/llvm/lib/Support/Mustache.cpp
index 8139e9eb4717f..829643d1f35d2 100644
--- a/llvm/lib/Support/Mustache.cpp
+++ b/llvm/lib/Support/Mustache.cpp
@@ -590,9 +590,16 @@ void Parser::parseSection(ASTNode *Parent, ASTNode::Type Ty,
   size_t Start = CurrentPtr;
   parseMustache(CurrentNode);
   const size_t End = CurrentPtr - 1;
+
+  size_t RawBodySize = 0;
+  for (size_t I = Start; I < End; ++I)
+    RawBodySize += Tokens[I].RawBody.size();
+
   SmallString<128> RawBody;
-  for (std::size_t I = Start; I < End; I++)
+  RawBody.reserve(RawBodySize);
+  for (std::size_t I = Start; I < End; ++I)
     RawBody += Tokens[I].RawBody;
+
   CurrentNode->setRawBody(Ctx.Saver.save(StringRef(RawBody)));
   Parent->addChild(CurrentNode);
 }