sammccall created this revision.
sammccall added a reviewer: kadircet.
Herald added a project: All.
sammccall requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
After building a PCH, the vector capacity is on average ~1/3 unused.
If we're going to keep it in memory for a while, reallocate to the right size.
Take care to do this once clang is destroyed so that we can reuse its
memory rather than requesting more.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D124242
Files:
clang/lib/Frontend/PrecompiledPreamble.cpp
Index: clang/lib/Frontend/PrecompiledPreamble.cpp
===================================================================
--- clang/lib/Frontend/PrecompiledPreamble.cpp
+++ clang/lib/Frontend/PrecompiledPreamble.cpp
@@ -374,6 +374,15 @@
return StringRef(Memory->Data.data(), Memory->Data.size());
}
+ // Shrink in-memory buffers to fit.
+ // This incurs a copy, but preambles tend to be long-lived.
+ // Only safe to call once nothing can alias the buffer.
+ void shrink() {
+ if (!Memory)
+ return;
+ Memory->Data = decltype(Memory->Data)(Memory->Data);
+ }
+
private:
PCHStorage() = default;
PCHStorage(const PCHStorage &) = delete;
@@ -520,7 +529,7 @@
if (!Act->hasEmittedPreamblePCH())
return BuildPreambleError::CouldntEmitPCH;
- Act.reset(); // Frees the PCH buffer frees, unless Storage keeps it in
memory.
+ Act.reset(); // Frees the PCH buffer, unless Storage keeps it in memory.
// Keep track of all of the files that the source manager knows about,
// so we can verify whether they have changed or not.
@@ -545,6 +554,11 @@
}
}
+ // Shrinking the storage requires extra temporary memory.
+ // Destroying clang first reduces peak memory usage.
+ CICleanup.unregister();
+ Clang.reset();
+ Storage->shrink();
return PrecompiledPreamble(
std::move(Storage), std::move(PreambleBytes), PreambleEndsAtStartOfLine,
std::move(FilesInPreamble), std::move(MissingFiles));
Index: clang/lib/Frontend/PrecompiledPreamble.cpp
===================================================================
--- clang/lib/Frontend/PrecompiledPreamble.cpp
+++ clang/lib/Frontend/PrecompiledPreamble.cpp
@@ -374,6 +374,15 @@
return StringRef(Memory->Data.data(), Memory->Data.size());
}
+ // Shrink in-memory buffers to fit.
+ // This incurs a copy, but preambles tend to be long-lived.
+ // Only safe to call once nothing can alias the buffer.
+ void shrink() {
+ if (!Memory)
+ return;
+ Memory->Data = decltype(Memory->Data)(Memory->Data);
+ }
+
private:
PCHStorage() = default;
PCHStorage(const PCHStorage &) = delete;
@@ -520,7 +529,7 @@
if (!Act->hasEmittedPreamblePCH())
return BuildPreambleError::CouldntEmitPCH;
- Act.reset(); // Frees the PCH buffer frees, unless Storage keeps it in memory.
+ Act.reset(); // Frees the PCH buffer, unless Storage keeps it in memory.
// Keep track of all of the files that the source manager knows about,
// so we can verify whether they have changed or not.
@@ -545,6 +554,11 @@
}
}
+ // Shrinking the storage requires extra temporary memory.
+ // Destroying clang first reduces peak memory usage.
+ CICleanup.unregister();
+ Clang.reset();
+ Storage->shrink();
return PrecompiledPreamble(
std::move(Storage), std::move(PreambleBytes), PreambleEndsAtStartOfLine,
std::move(FilesInPreamble), std::move(MissingFiles));
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
