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Bitcode: Add a string table to the bitcode format.

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Add a top-level STRTAB block containing a string table blob, and start storing
strings for module codes FUNCTION, GLOBALVAR, ALIAS, IFUNC and COMDAT in
the string table.

This change allows us to share names between globals and comdats as well
as between modules, and improves the efficiency of loading bitcode files by
no longer using a bit encoding for symbol names. Once we start writing the
irsymtab to the bitcode file we will also be able to share strings between
it and the module.

On my machine, link time for Chromium for Linux with ThinLTO decreases by
about 7% for no-op incremental builds or about 1% for full builds. Total
bitcode file size decreases by about 3%.

As discussed on llvm-dev:
http://lists.llvm.org/pipermail/llvm-dev/2017-April/111732.html

Differential Revision: https://reviews.llvm.org/D31838

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300464 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Peter Collingbourne
2017-04-17 17:51:36 +00:00
parent 0c79d1f4e0
commit 6163b4af73
21 changed files with 674 additions and 439 deletions
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25
test/Bitcode/thinlto-function-summary.ll
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@@ -2,9 +2,19 @@
; RUN: opt -passes=name-anon-globals -module-summary < %s | llvm-bcanalyzer -dump | FileCheck %s -check-prefix=BC
; Check for summary block/records.
; Check the value ids in the summary entries against the
; same in the ValueSumbolTable, to ensure the ordering is stable.
; Also check the linkage field on the summary entries.
; BC: <SOURCE_FILENAME
; "h"
; BC-NEXT: <GLOBALVAR {{.*}} op0=0 op1=1
; "foo"
; BC-NEXT: <FUNCTION op0=1 op1=3
; "bar"
; BC-NEXT: <FUNCTION op0=4 op1=3
; "anon.[32 chars].0"
; BC-NEXT: <FUNCTION op0=7 op1=39
; "variadic"
; BC-NEXT: <FUNCTION op0=46 op1=8
; "f"
; BC-NEXT: <ALIAS op0=54 op1=1
; BC: <GLOBALVAL_SUMMARY_BLOCK
; BC-NEXT: <VERSION
; BC-NEXT: <PERMODULE {{.*}} op0=1 op1=0
@@ -13,13 +23,8 @@
; BC-NEXT: <PERMODULE {{.*}} op0=4 op1=16
; BC-NEXT: <ALIAS {{.*}} op0=5 op1=0 op2=3
; BC-NEXT: </GLOBALVAL_SUMMARY_BLOCK
; BC-NEXT: <VALUE_SYMTAB
; BC-NEXT: <FNENTRY {{.*}} op0=4 {{.*}}> record string = 'variadic'
; BC-NEXT: <FNENTRY {{.*}} op0=1 {{.*}}> record string = 'foo'
; BC-NEXT: <FNENTRY {{.*}} op0=2 {{.*}}> record string = 'bar'
; BC-NEXT: <ENTRY {{.*}} op0=5 {{.*}}> record string = 'f'
; BC-NEXT: <ENTRY {{.*}} record string = 'h'
; BC-NEXT: <FNENTRY {{.*}} op0=3 {{.*}}> record string = 'anon.
; BC: <STRTAB_BLOCK
; BC-NEXT: blob data = 'hfoobaranon.{{................................}}.0variadicf'
; RUN: opt -name-anon-globals -module-summary < %s | llvm-dis | FileCheck %s