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[Dwarf] Optimize getOrCreateSourceID() for repeated calls on same file (NFCI) 

DwarfCompileUnit::getOrCreateSourceID() is often called many times
in sequence with the same DIFile. This is currently very expensive,
because it involves creating a string from directory and file name
and looking it up in a string map. This patch remembers the last
DIFile and its ID and directly returns that.

This gives a geomean -1.3% compile-time improvement on CTMark O0-g.

Differential Revision: https://reviews.llvm.org/D118041
This commit is contained in:
Nikita Popov 2022-01-24 14:29:05 +01:00
parent 70cb8daed4
commit 9554aaa275
2 changed files with 11 additions and 3 deletions
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7
llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
View File

@ -127,9 +127,14 @@ unsigned DwarfCompileUnit::getOrCreateSourceID(const DIFile *File) {
if (!File)
return Asm->OutStreamer->emitDwarfFileDirective(0, "", "", None, None,
CUID);
return Asm->OutStreamer->emitDwarfFileDirective(
if (LastFile != File) {
LastFile = File;
LastFileID = Asm->OutStreamer->emitDwarfFileDirective(
0, File->getDirectory(), File->getFilename(), DD->getMD5AsBytes(File),
File->getSource(), CUID);
}
return LastFileID;
}
DIE *DwarfCompileUnit::getOrCreateGlobalVariableDIE(

3
llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.h
View File

@ -86,6 +86,9 @@ class DwarfCompileUnit final : public DwarfUnit {
/// DWO ID for correlating skeleton and split units.
uint64_t DWOId = 0;
const DIFile *LastFile = nullptr;
unsigned LastFileID;
/// Construct a DIE for the given DbgVariable without initializing the
/// DbgVariable's DIE reference.
DIE *constructVariableDIEImpl(const DbgVariable &DV, bool Abstract);