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[IROutliner] Ensure instructions at end of candidate are excluded
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Occasionally instructions are between the last instruction in a region,
and the following instruction as identified by the Candidate.  This
adds an extra check right before splitting a candidate that excludes the region from being split/checked for outlining to remove errors.

Tests Added:
Tranforms/IROuutliner/outlining-extra-bitcasts.ll

Reviewer: paquette, jroelofs

Differential Revision: https://reviews.llvm.org/D104142
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@AndrewLitteken
AndrewLitteken committed Aug 30, 2021
1 parent 5b3fad4 commit f564299
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Showing 2 changed files with 96 additions and 50 deletions.
20 changes: 18 additions & 2 deletions llvm/lib/Transforms/IPO/IROutliner.cpp
View file
Expand Up @@ -133,9 +133,18 @@ static void moveBBContents(BasicBlock &SourceBB, BasicBlock &TargetBB) {
void OutlinableRegion::splitCandidate() {
assert(!CandidateSplit && "Candidate already split!");

Instruction *StartInst = (*Candidate->begin()).Inst;
Instruction *EndInst = (*Candidate->end()).Inst;
assert(StartInst && EndInst && "Expected a start and end instruction?");
assert(EndInst && "Expected an end instruction?");

// We check if the current instruction following the last instruction in the
// region is the same as the recorded instruction following the last
// instruction. If they do not match, there could be problems in rewriting
// the program after outlining, so we ignore it.
if (EndInst != Candidate->backInstruction()->getNextNonDebugInstruction())
return;

Instruction *StartInst = (*Candidate->begin()).Inst;
assert(StartInst && "Expected a start instruction?");
StartBB = StartInst->getParent();
PrevBB = StartBB;

Expand Down Expand Up @@ -1687,6 +1696,13 @@ unsigned IROutliner::doOutline(Module &M) {
// Break the outlinable region out of its parent BasicBlock into its own
// BasicBlocks (see function implementation).
OS->splitCandidate();

// There's a chance that when the region is split, extra instructions are
// added to the region. This makes the region no longer viable
// to be split, so we ignore it for outlining.
if (!OS->CandidateSplit)
continue;

std::vector<BasicBlock *> BE = {OS->StartBB};
OS->CE = new (ExtractorAllocator.Allocate())
CodeExtractor(BE, nullptr, false, nullptr, nullptr, nullptr, false,
Expand Down
126 changes: 78 additions & 48 deletions llvm/test/Transforms/IROutliner/outlining-bitcasts.ll
View file
@@ -1,4 +1,4 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --include-generated-funcs
; RUN: opt -S -verify -iroutliner -ir-outlining-no-cost < %s | FileCheck %s

; This test ensures that an extra output is not added when there is a bitcast
Expand All @@ -12,15 +12,6 @@ declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)
declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture)

define void @outline_bitcast_base() {
; CHECK-LABEL: @outline_bitcast_base(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[B:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[C:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[D:%.*]] = alloca i32, align 4
; CHECK-NEXT: call void @[[FUNCTION_0:.*]](i32* [[A]], i32* [[B]], i32* [[C]], i32* [[D]])
; CHECK-NEXT: ret void
;
entry:
%a = alloca i32, align 4
%b = alloca i32, align 4
Expand All @@ -37,25 +28,6 @@ entry:
}

define void @outline_bitcast_removed() {
; CHECK-LABEL: @outline_bitcast_removed(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[B:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[C:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[D:%.*]] = alloca i32, align 4
; CHECK-NEXT: call void @[[FUNCTION_0:.*]](i32* [[A]], i32* [[B]], i32* [[C]], i32* [[D]])
; CHECK-NEXT: [[LT_CAST1:%.*]] = bitcast i32* [[D]] to i8*
; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 -1, i8* [[LT_CAST1]])
; CHECK-NEXT: [[AM:%.*]] = load i32, i32* [[B]], align 4
; CHECK-NEXT: [[BM:%.*]] = load i32, i32* [[A]], align 4
; CHECK-NEXT: [[CM:%.*]] = load i32, i32* [[C]], align 4
; CHECK-NEXT: [[AS:%.*]] = add i32 [[AM]], [[BM]]
; CHECK-NEXT: [[BS:%.*]] = add i32 [[BM]], [[AM]]
; CHECK-NEXT: [[CS:%.*]] = add i32 [[BM]], [[CM]]
; CHECK-NEXT: [[LT_CAST:%.*]] = bitcast i32* [[D]] to i8*
; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 -1, i8* [[LT_CAST]])
; CHECK-NEXT: ret void
;
entry:
%a = alloca i32, align 4
%b = alloca i32, align 4
Expand All @@ -72,34 +44,92 @@ entry:
%am = load i32, i32* %b
%bm = load i32, i32* %a
%cm = load i32, i32* %c
%as = add i32 %am, %bm
%bs = add i32 %bm, %am
%cs = add i32 %bm, %cm
call void @llvm.lifetime.end.p0i8(i64 -1, i8* %X)
ret void
}

; The first bitcast is moved down to lifetime start, and, since the original
; endpoint does not match the new endpoint, we cannot extract and outline the
; second bitcast and set of adds. Outlining only occurs in this case due to
; the lack of a cost model, as denoted by the debug command line argument.

define void @outline_bitcast_base2(i32 %a, i32 %b, i32 %c) {
; CHECK-LABEL: @outline_bitcast_base2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[AL:%.*]] = add i32 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[BL:%.*]] = add i32 [[B]], [[A]]
; CHECK-NEXT: [[CL:%.*]] = add i32 [[B]], [[C:%.*]]
; CHECK-NEXT: ret void
;
entry:
%d = alloca i32, align 4
%X = bitcast i32* %d to i8*
%al = add i32 %a, %b
%bl = add i32 %b, %a
%cl = add i32 %b, %c
%buffer = mul i32 %a, %b
%Y = bitcast i32* %d to i8*
%am = add i32 %a, %b
%bm = add i32 %b, %a
%cm = add i32 %b, %c
call void @llvm.lifetime.start.p0i8(i64 -1, i8* %X)
call void @llvm.lifetime.end.p0i8(i64 -1, i8* %X)
ret void
}

; CHECK: define internal void @[[FUNCTION_0]](i32* [[ARG0:%.*]], i32* [[ARG1:%.*]], i32* [[ARG2:%.*]], i32* [[ARG3:%.*]])
; CHECK: entry_to_outline:
; CHECK-NEXT: store i32 2, i32* [[ARG0]], align 4
; CHECK-NEXT: store i32 3, i32* [[ARG1]], align 4
; CHECK-NEXT: store i32 4, i32* [[ARG2]], align 4
; CHECK-NEXT: [[X:%.*]] = bitcast i32* [[ARG3]] to i8*
; CHECK-NEXT: [[AL:%.*]] = load i32, i32* [[ARG0]], align 4
; CHECK-NEXT: [[BL:%.*]] = load i32, i32* [[ARG1]], align 4
; CHECK-NEXT: [[CL:%.*]] = load i32, i32* [[ARG2]], align 4
; CHECK-LABEL: @outline_bitcast_base(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[B:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[C:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[D:%.*]] = alloca i32, align 4
; CHECK-NEXT: call void @outlined_ir_func_0(i32* [[A]], i32* [[B]], i32* [[C]], i32* [[D]])
; CHECK-NEXT: ret void
;
;
; CHECK-LABEL: @outline_bitcast_removed(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[A:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[B:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[C:%.*]] = alloca i32, align 4
; CHECK-NEXT: [[D:%.*]] = alloca i32, align 4
; CHECK-NEXT: call void @outlined_ir_func_0(i32* [[A]], i32* [[B]], i32* [[C]], i32* [[D]])
; CHECK-NEXT: [[LT_CAST1:%.*]] = bitcast i32* [[D]] to i8*
; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 -1, i8* [[LT_CAST1]])
; CHECK-NEXT: [[AM:%.*]] = load i32, i32* [[B]], align 4
; CHECK-NEXT: [[BM:%.*]] = load i32, i32* [[A]], align 4
; CHECK-NEXT: [[CM:%.*]] = load i32, i32* [[C]], align 4
; CHECK-NEXT: [[LT_CAST:%.*]] = bitcast i32* [[D]] to i8*
; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 -1, i8* [[LT_CAST]])
; CHECK-NEXT: ret void
;
;
; CHECK-LABEL: @outline_bitcast_base2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[D:%.*]] = alloca i32, align 4
; CHECK-NEXT: call void @outlined_ir_func_1(i32* [[D]], i32 [[A:%.*]], i32 [[B:%.*]], i32 [[C:%.*]])
; CHECK-NEXT: [[BUFFER:%.*]] = mul i32 [[A]], [[B]]
; CHECK-NEXT: [[Y:%.*]] = bitcast i32* [[D]] to i8*
; CHECK-NEXT: [[AM:%.*]] = add i32 [[A]], [[B]]
; CHECK-NEXT: [[BM:%.*]] = add i32 [[B]], [[A]]
; CHECK-NEXT: [[CM:%.*]] = add i32 [[B]], [[C]]
; CHECK-NEXT: [[LT_CAST1:%.*]] = bitcast i32* [[D]] to i8*
; CHECK-NEXT: call void @llvm.lifetime.start.p0i8(i64 -1, i8* [[LT_CAST1]])
; CHECK-NEXT: [[LT_CAST:%.*]] = bitcast i32* [[D]] to i8*
; CHECK-NEXT: call void @llvm.lifetime.end.p0i8(i64 -1, i8* [[LT_CAST]])
; CHECK-NEXT: ret void
;
;
; CHECK: @outlined_ir_func_0(i32* [[TMP0:%.*]], i32* [[TMP1:%.*]], i32* [[TMP2:%.*]], i32* [[TMP3:%.*]])
; CHECK: entry_to_outline:
; CHECK-NEXT: store i32 2, i32* [[TMP0:%.*]], align 4
; CHECK-NEXT: store i32 3, i32* [[TMP1:%.*]], align 4
; CHECK-NEXT: store i32 4, i32* [[TMP2:%.*]], align 4
; CHECK-NEXT: [[X:%.*]] = bitcast i32* [[TMP3:%.*]] to i8*
; CHECK-NEXT: [[AL:%.*]] = load i32, i32* [[TMP0]], align 4
; CHECK-NEXT: [[BL:%.*]] = load i32, i32* [[TMP1]], align 4
; CHECK-NEXT: [[CL:%.*]] = load i32, i32* [[TMP2]], align 4
; CHECK-NEXT: br label [[ENTRY_AFTER_OUTLINE_EXITSTUB:%.*]]
;
;
; CHECK: @outlined_ir_func_1(i32* [[TMP0:%.*]], i32 [[TMP1:%.*]], i32 [[TMP2:%.*]], i32 [[TMP3:%.*]])
; CHECK: entry_to_outline:
; CHECK-NEXT: [[X:%.*]] = bitcast i32* [[TMP0]] to i8*
; CHECK-NEXT: [[AL:%.*]] = add i32 [[TMP1]], [[TMP2]]
; CHECK-NEXT: [[BL:%.*]] = add i32 [[TMP2]], [[TMP1]]
; CHECK-NEXT: [[CL:%.*]] = add i32 [[TMP2]], [[TMP3]]
; CHECK-NEXT: br label [[ENTRY_AFTER_OUTLINE_EXITSTUB:%.*]]
;

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