[llvm] r345524 - [HotColdSplitting] Allow outlining single-block cold regions
Vedant Kumar via llvm-commits
llvm-commits at lists.llvm.org
Mon Oct 29 12:15:39 PDT 2018
Author: vedantk
Date: Mon Oct 29 12:15:39 2018
New Revision: 345524
URL: http://llvm.org/viewvc/llvm-project?rev=345524&view=rev
Log:
[HotColdSplitting] Allow outlining single-block cold regions
It can be profitable to outline single-block cold regions because they
may be large.
Allow outlining single-block regions if they have over some threshold of
non-debug, non-terminator instructions. I chose 3 as the threshold after
experimenting with several internal frameworks.
In practice, reducing the threshold further did not give much
improvement, whereas increasing it resulted in substantial regressions.
Differential Revision: https://reviews.llvm.org/D53824
Modified:
llvm/trunk/lib/Transforms/IPO/HotColdSplitting.cpp
llvm/trunk/test/Transforms/HotColdSplit/do-not-split.ll
llvm/trunk/test/Transforms/HotColdSplit/minsize.ll
llvm/trunk/test/Transforms/HotColdSplit/split-out-dbg-val-of-arg.ll
Modified: llvm/trunk/lib/Transforms/IPO/HotColdSplitting.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/HotColdSplitting.cpp?rev=345524&r1=345523&r2=345524&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/HotColdSplitting.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/HotColdSplitting.cpp Mon Oct 29 12:15:39 2018
@@ -31,6 +31,7 @@
#include "llvm/IR/Function.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassManager.h"
@@ -65,6 +66,10 @@ using namespace llvm;
static cl::opt<bool> EnableStaticAnalyis("hot-cold-static-analysis",
cl::init(true), cl::Hidden);
+static cl::opt<unsigned> MinOutliningInstCount(
+ "min-outlining-inst-count", cl::init(3), cl::Hidden,
+ cl::desc("Minimum number of instructions needed for a single-block region "
+ "to be an outlining candidate"));
namespace {
@@ -130,6 +135,19 @@ static bool mayExtractBlock(const BasicB
return !BB.hasAddressTaken();
}
+/// Check whether \p BB has at least \p Min non-debug, non-terminator
+/// instructions.
+static bool hasMinimumInstCount(const BasicBlock &BB, unsigned Min) {
+ unsigned Count = 0;
+ for (const Instruction &I : BB) {
+ if (isa<DbgInfoIntrinsic>(&I) || &I == BB.getTerminator())
+ continue;
+ if (++Count >= Min)
+ return true;
+ }
+ return false;
+}
+
/// Identify the maximal region of cold blocks which includes \p SinkBB.
///
/// Include all blocks post-dominated by \p SinkBB, \p SinkBB itself, and all
@@ -223,9 +241,8 @@ findMaximalColdRegion(BasicBlock &SinkBB
++SuccIt;
}
- // TODO: Consider outlining regions with just 1 block, but more than some
- // threshold of instructions.
- if (ColdRegion.size() == 1)
+ if (ColdRegion.size() == 1 &&
+ !hasMinimumInstCount(*ColdRegion[0], MinOutliningInstCount))
return {};
return ColdRegion;
Modified: llvm/trunk/test/Transforms/HotColdSplit/do-not-split.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/HotColdSplit/do-not-split.ll?rev=345524&r1=345523&r2=345524&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/HotColdSplit/do-not-split.ll (original)
+++ llvm/trunk/test/Transforms/HotColdSplit/do-not-split.ll Mon Oct 29 12:15:39 2018
@@ -6,7 +6,7 @@
; The cold region is too small to split.
; CHECK-LABEL: @foo
-; CHECK-NOT: codeRepl
+; CHECK-NOT: foo.cold.1
define void @foo() {
entry:
br i1 undef, label %if.then, label %if.end
@@ -15,21 +15,28 @@ if.then:
unreachable
if.end: ; preds = %entry
- br label %if.then12
+ ret void
+}
-if.then12: ; preds = %if.end
- br label %cleanup40
+; The cold region is still too small to split.
+; CHECK-LABEL: @bar
+; CHECK-NOT: bar.cold.1
+define void @bar() {
+entry:
+ br i1 undef, label %if.then, label %if.end
-cleanup40: ; preds = %if.then12
- br label %return
+if.then: ; preds = %entry
+ call void @sink()
+ call void @sink()
+ ret void
-return: ; preds = %cleanup40
+if.end: ; preds = %entry
ret void
}
; Make sure we don't try to outline the entire function.
; CHECK-LABEL: @fun
-; CHECK-NOT: codeRepl
+; CHECK-NOT: fun.cold.1
define void @fun() {
entry:
br i1 undef, label %if.then, label %if.end
@@ -43,14 +50,53 @@ if.end:
; Don't outline infinite loops.
; CHECK-LABEL: @infinite_loop
-; CHECK-NOT: codeRepl
+; CHECK-NOT: infinite_loop.cold.1
define void @infinite_loop() {
entry:
br label %loop
loop:
call void @sink()
+ call void @sink()
+ call void @sink()
br label %loop
}
+; Don't count debug intrinsics towards the outlining threshold.
+; CHECK-LABEL: @dont_count_debug_intrinsics
+; CHECK-NOT: dont_count_debug_intrinsics.cold.1
+define void @dont_count_debug_intrinsics(i32 %arg1) !dbg !6 {
+entry:
+ %var = add i32 0, 0, !dbg !11
+ br i1 undef, label %if.then, label %if.end
+
+if.then: ; preds = %entry
+ ret void
+
+if.end: ; preds = %entry
+ call void @llvm.dbg.value(metadata i32 %arg1, metadata !9, metadata !DIExpression()), !dbg !11
+ call void @llvm.dbg.value(metadata i32 %arg1, metadata !9, metadata !DIExpression()), !dbg !11
+ call void @sink()
+ ret void
+}
+
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
declare void @sink() cold
+
+!llvm.dbg.cu = !{!0}
+!llvm.debugify = !{!3, !4}
+!llvm.module.flags = !{!5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C, file: !1, producer: "debugify", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "<stdin>", directory: "/")
+!2 = !{}
+!3 = !{i32 7}
+!4 = !{i32 1}
+!5 = !{i32 2, !"Debug Info Version", i32 3}
+!6 = distinct !DISubprogram(name: "dont_count_debug_intrinsics", linkageName: "dont_count_debug_intrinsics", scope: null, file: !1, line: 1, type: !7, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: true, unit: !0, retainedNodes: !8)
+!7 = !DISubroutineType(types: !2)
+!8 = !{!9}
+!9 = !DILocalVariable(name: "1", scope: !6, file: !1, line: 1, type: !10)
+!10 = !DIBasicType(name: "ty32", size: 32, encoding: DW_ATE_unsigned)
+!11 = !DILocation(line: 1, column: 1, scope: !6)
Modified: llvm/trunk/test/Transforms/HotColdSplit/minsize.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/HotColdSplit/minsize.ll?rev=345524&r1=345523&r2=345524&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/HotColdSplit/minsize.ll (original)
+++ llvm/trunk/test/Transforms/HotColdSplit/minsize.ll Mon Oct 29 12:15:39 2018
@@ -1,8 +1,7 @@
; RUN: opt -hotcoldsplit -S < %s | FileCheck %s
; CHECK-LABEL: @fun
-; CHECK: codeRepl:
-; CHECK-NEXT: call void @fun.cold.1
+; CHECK: call void @fun.cold.1
define void @fun() {
entry:
@@ -12,21 +11,13 @@ if.then:
ret void
if.else:
- br label %if.then4
-
-if.then4:
- br i1 undef, label %if.then5, label %if.end
-
-if.then5:
- br label %cleanup
-
-if.end:
- br label %cleanup
-
-cleanup:
- %cleanup.dest.slot.0 = phi i32 [ 1, %if.then5 ], [ 0, %if.end ]
- unreachable
+ call void @sink()
+ call void @sink()
+ call void @sink()
+ ret void
}
+declare void @sink() cold
+
; CHECK: define {{.*}} @fun.cold.1{{.*}}#[[outlined_func_attr:[0-9]+]]
; CHECK: attributes #[[outlined_func_attr]] = { {{.*}}minsize
Modified: llvm/trunk/test/Transforms/HotColdSplit/split-out-dbg-val-of-arg.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/HotColdSplit/split-out-dbg-val-of-arg.ll?rev=345524&r1=345523&r2=345524&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/HotColdSplit/split-out-dbg-val-of-arg.ll (original)
+++ llvm/trunk/test/Transforms/HotColdSplit/split-out-dbg-val-of-arg.ll Mon Oct 29 12:15:39 2018
@@ -6,33 +6,23 @@
define void @foo(i32 %arg1) !dbg !6 {
entry:
%var = add i32 0, 0, !dbg !11
- br i1 undef, label %if.then, label %if.end, !dbg !12
+ br i1 undef, label %if.then, label %if.end
if.then: ; preds = %entry
- ret void, !dbg !13
+ ret void
if.end: ; preds = %entry
call void @llvm.dbg.value(metadata i32 %arg1, metadata !9, metadata !DIExpression()), !dbg !11
- br label %if.then12, !dbg !14
-
-if.then12: ; preds = %if.end
- br label %cleanup40, !dbg !15
-
-cleanup40: ; preds = %if.then12
- br i1 undef, label %if.then5, label %if.end1, !dbg !16
-
-if.then5:
- br label %return, !dbg !17
-
-if.end1:
- br label %return, !dbg !18
-
-return: ; preds = %cleanup40
- unreachable, !dbg !19
+ call void @sink()
+ call void @sink()
+ call void @sink()
+ ret void
}
declare void @llvm.dbg.value(metadata, metadata, metadata)
+declare void @sink() cold
+
!llvm.dbg.cu = !{!0}
!llvm.debugify = !{!3, !4}
!llvm.module.flags = !{!5}
@@ -49,11 +39,3 @@ declare void @llvm.dbg.value(metadata, m
!9 = !DILocalVariable(name: "1", scope: !6, file: !1, line: 1, type: !10)
!10 = !DIBasicType(name: "ty32", size: 32, encoding: DW_ATE_unsigned)
!11 = !DILocation(line: 1, column: 1, scope: !6)
-!12 = !DILocation(line: 2, column: 1, scope: !6)
-!13 = !DILocation(line: 3, column: 1, scope: !6)
-!14 = !DILocation(line: 4, column: 1, scope: !6)
-!15 = !DILocation(line: 5, column: 1, scope: !6)
-!16 = !DILocation(line: 6, column: 1, scope: !6)
-!17 = !DILocation(line: 7, column: 1, scope: !6)
-!18 = !DILocation(line: 8, column: 1, scope: !6)
-!19 = !DILocation(line: 9, column: 1, scope: !6)
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