[thinlto] Basic thinlto fdo heuristic

Summary:
This patch improves thinlto importer
by importing 3x larger functions that are called from hot block.

I compared performance with the trunk on spec, and there
were about 2% on povray and 3.33% on milc. These results seems
to be consistant and match the results Teresa got with her simple
heuristic. Some benchmarks got slower but I think they are just
noisy (mcf, xalancbmki, omnetpp)- running the benchmarks again with
more iterations to confirm. Geomean of all benchmarks including the noisy ones
were about +0.02%.

I see much better improvement on google branch with Easwaran patch
for pgo callsite inlining (the inliner actually inline those big functions)
Over all I see +0.5% improvement, and I get +8.65% on povray.
So I guess we will see much bigger change when Easwaran patch will land
(it depends on new pass manager), but it is still worth putting this to trunk
before it.

Implementation details changes:
- Removed CallsiteCount.
- ProfileCount got replaced by Hotness
- hot-import-multiplier is set to 3.0 for now,
didn't have time to tune it up, but I see that we get most of the interesting
functions with 3, so there is no much performance difference with higher, and
binary size doesn't grow as much as with 10.0.

Reviewers: eraman, mehdi_amini, tejohnson

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D24638

llvm-svn: 282437

1 files changed, 13 insertions, 4 deletions

diff --git a/llvm/test/Bitcode/thinlto-function-summary-callgraph-pgo.ll b/llvm/test/Bitcode/thinlto-function-summary-callgraph-pgo.ll
index a927a16be15..713e36dd14d 100644
--- a/llvm/test/Bitcode/thinlto-function-summary-callgraph-pgo.ll
+++ b/llvm/test/Bitcode/thinlto-function-summary-callgraph-pgo.ll
@@ -1,15 +1,20 @@
 ; Test to check the callgraph in summary when there is PGO
 ; RUN: opt -module-summary %s -o %t.o
 ; RUN: llvm-bcanalyzer -dump %t.o | FileCheck %s
+
 ; RUN: opt -module-summary %p/Inputs/thinlto-function-summary-callgraph.ll -o %t2.o
 ; RUN: llvm-lto -thinlto -o %t3 %t.o %t2.o
 ; RUN: llvm-bcanalyzer -dump %t3.thinlto.bc | FileCheck %s --check-prefix=COMBINED
 
+; Check parsing for old summary versions generated from this file.
+; RUN: llvm-lto -thinlto-index-stats %p/Inputs/thinlto-function-summary-callgraph-pgo.1.bc  | FileCheck %s --check-prefix=OLD
+; RUN: llvm-lto -thinlto-index-stats %p/Inputs/thinlto-function-summary-callgraph-pgo-combined.1.bc  | FileCheck %s --check-prefix=OLD-COMBINED
+
 ; CHECK:       <GLOBALVAL_SUMMARY_BLOCK
 ; CHECK-NEXT:    <VERSION
 ; See if the call to func is registered, using the expected callsite count
-; and profile count, with value id matching the subsequent value symbol table.
-; CHECK-NEXT:    <PERMODULE_PROFILE {{.*}} op4=[[FUNCID:[0-9]+]] op5=1 op6=1/>
+; and hotness type, with value id matching the subsequent value symbol table.
+; CHECK-NEXT:    <PERMODULE_PROFILE {{.*}} op4=[[FUNCID:[0-9]+]] op5=2/>
 ; CHECK-NEXT:  </GLOBALVAL_SUMMARY_BLOCK>
 ; CHECK-NEXT:  <VALUE_SYMTAB
 ; CHECK-NEXT:    <FNENTRY {{.*}} record string = 'main'
@@ -21,8 +26,9 @@
 ; COMBINED-NEXT:    <VERSION
 ; COMBINED-NEXT:    <COMBINED
 ; See if the call to func is registered, using the expected callsite count
-; and profile count, with value id matching the subsequent value symbol table.
-; COMBINED-NEXT:    <COMBINED_PROFILE {{.*}} op5=[[FUNCID:[0-9]+]] op6=1 op7=1/>
+; and hotness type, with value id matching the subsequent value symbol table.
+; op6=2 which is hotnessType::None.
+; COMBINED-NEXT:    <COMBINED_PROFILE {{.*}} op5=[[FUNCID:[0-9]+]] op6=2/>
 ; COMBINED-NEXT:  </GLOBALVAL_SUMMARY_BLOCK>
 ; COMBINED-NEXT:  <VALUE_SYMTAB
 ; Entry for function func should have entry with value id FUNCID
@@ -44,3 +50,6 @@ entry:
 declare void @func(...) #1
 
 !2 = !{!"function_entry_count", i64 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)