<div dir="ltr">Certainly seems like a thing we might want to try - though it'd help to have a reminder/description of why shrinking these fields to these specific bit sizes is valid (are the already restricted to those sizes in other places/ways, for example - point to where/how they're already so restricted)</div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Apr 8, 2016 at 7:08 PM, Davide Italiano via llvm-commits <span dir="ltr"><<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">davide created this revision.<br>
davide added reviewers: dexonsmith, aprantl, echristo, dblaikie.<br>
davide added a subscriber: llvm-commits.<br>
<br>
I started this effort after noticing that DI shows up as a considerable portion of memory usage during an LTO build (of clang, and others).<br>
This is roughly the data I got (peak usage):<br>
DISubprogram: 228MB<br>
DILocalVariable: 164MB<br>
The proposed patch packs field slightly more efficiently reducing the size of DISubprogram from 48bytes to 40bytes and of DILocalVariable from 40 bytes to 32 bytes.<br>
The saving overall in memory is ~70MB.<br>
This is still to be considered WIP as this breaks 4 tests in the LLVM suite (which I'm currently investigating), but I wanted to have some eyes on it as DebugInfo seems to be of interest of many these days.<br>
<br>
<a href="http://reviews.llvm.org/D18918" rel="noreferrer" target="_blank">http://reviews.llvm.org/D18918</a><br>
<br>
Files:<br>
include/llvm/IR/DebugInfoMetadata.h<br>
<br>
Index: include/llvm/IR/DebugInfoMetadata.h<br>
===================================================================<br>
--- include/llvm/IR/DebugInfoMetadata.h<br>
+++ include/llvm/IR/DebugInfoMetadata.h<br>
@@ -1229,21 +1229,21 @@<br>
<br>
unsigned Line;<br>
unsigned ScopeLine;<br>
- unsigned Virtuality;<br>
unsigned VirtualIndex;<br>
- unsigned Flags;<br>
- bool IsLocalToUnit;<br>
- bool IsDefinition;<br>
- bool IsOptimized;<br>
+ unsigned Virtuality:2;<br>
+ unsigned Flags:27;<br>
+ bool IsLocalToUnit:1;<br>
+ bool IsDefinition:1;<br>
+ bool IsOptimized:1;<br>
<br>
DISubprogram(LLVMContext &C, StorageType Storage, unsigned Line,<br>
- unsigned ScopeLine, unsigned Virtuality, unsigned VirtualIndex,<br>
+ unsigned ScopeLine, unsigned VirtualIndex, unsigned Virtuality,<br>
unsigned Flags, bool IsLocalToUnit, bool IsDefinition,<br>
bool IsOptimized, ArrayRef<Metadata *> Ops)<br>
: DILocalScope(C, DISubprogramKind, Storage, dwarf::DW_TAG_subprogram,<br>
Ops),<br>
- Line(Line), ScopeLine(ScopeLine), Virtuality(Virtuality),<br>
- VirtualIndex(VirtualIndex), Flags(Flags), IsLocalToUnit(IsLocalToUnit),<br>
+ Line(Line), ScopeLine(ScopeLine), VirtualIndex(VirtualIndex),<br>
+ Virtuality(Virtuality), Flags(Flags), IsLocalToUnit(IsLocalToUnit),<br>
IsDefinition(IsDefinition), IsOptimized(IsOptimized) {}<br>
~DISubprogram() = default;<br>
<br>
@@ -1858,8 +1858,8 @@<br>
friend class LLVMContextImpl;<br>
friend class MDNode;<br>
<br>
- unsigned Arg;<br>
- unsigned Flags;<br>
+ unsigned Arg:16;<br>
+ unsigned Flags:16;<br>
<br>
DILocalVariable(LLVMContext &C, StorageType Storage, unsigned Line,<br>
unsigned Arg, unsigned Flags, ArrayRef<Metadata *> Ops)<br>
<br>
<br>
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<br></blockquote></div><br></div>