Bitcode: Add a string table to the bitcode format.

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

View File

@@ -10,30 +10,27 @@
; RUN: llvm-lto -thinlto-index-stats %p/Inputs/thinlto-function-summary-callgraph.1.bc | FileCheck %s --check-prefix=OLD
; RUN: llvm-lto -thinlto-index-stats %p/Inputs/thinlto-function-summary-callgraph-combined.1.bc | FileCheck %s --check-prefix=OLD-COMBINED
; CHECK: <SOURCE_FILENAME
; CHECK-NEXT: <FUNCTION
; "func"
; CHECK-NEXT: <FUNCTION op0=4 op1=4
; CHECK: <GLOBALVAL_SUMMARY_BLOCK
; CHECK-NEXT: <VERSION
; See if the call to func is registered, using the expected callsite count
; and value id matching the subsequent value symbol table.
; CHECK-NEXT: <PERMODULE {{.*}} op4=[[FUNCID:[0-9]+]]/>
; See if the call to func is registered.
; CHECK-NEXT: <PERMODULE {{.*}} op4=1/>
; CHECK-NEXT: </GLOBALVAL_SUMMARY_BLOCK>
; CHECK-NEXT: <VALUE_SYMTAB
; CHECK-NEXT: <FNENTRY {{.*}} record string = 'main'
; External function func should have entry with value id FUNCID
; CHECK-NEXT: <ENTRY {{.*}} op0=[[FUNCID]] {{.*}} record string = 'func'
; CHECK-NEXT: </VALUE_SYMTAB>
; CHECK: <STRTAB_BLOCK
; CHECK-NEXT: blob data = 'mainfunc'
; COMBINED: <GLOBALVAL_SUMMARY_BLOCK
; COMBINED-NEXT: <VERSION
; COMBINED-NEXT: <VALUE_GUID op0=[[FUNCID:[0-9]+]] op1=7289175272376759421/>
; COMBINED-NEXT: <VALUE_GUID
; COMBINED-NEXT: <COMBINED
; See if the call to func is registered, using the expected callsite count
; and value id matching the subsequent value symbol table.
; COMBINED-NEXT: <COMBINED {{.*}} op5=[[FUNCID:[0-9]+]]/>
; See if the call to func is registered.
; COMBINED-NEXT: <COMBINED {{.*}} op5=[[FUNCID]]/>
; COMBINED-NEXT: </GLOBALVAL_SUMMARY_BLOCK>
; COMBINED-NEXT: <VALUE_SYMTAB
; Entry for function func should have entry with value id FUNCID
; COMBINED-NEXT: <COMBINED_ENTRY {{.*}} op0=[[FUNCID]] op1=7289175272376759421/>
; COMBINED-NEXT: <COMBINED
; COMBINED-NEXT: </VALUE_SYMTAB>
; ModuleID = 'thinlto-function-summary-callgraph.ll'
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
@@ -49,4 +46,4 @@ entry:
declare void @func(...) #1
; OLD: Index {{.*}} contains 1 nodes (1 functions, 0 alias, 0 globals) and 1 edges (0 refs and 1 calls)
; OLD-COMBINED: Index {{.*}} contains 2 nodes (2 functions, 0 alias, 0 globals) and 1 edges (0 refs and 1 calls)
; OLD-COMBINED: Index {{.*}} contains 2 nodes (2 functions, 0 alias, 0 globals) and 1 edges (0 refs and 1 calls)