[llvm] r332685 - [MachineOutliner] Count savings from outlining in bytes.
Eli Friedman via llvm-commits
llvm-commits at lists.llvm.org
Thu May 17 18:52:16 PDT 2018
Author: efriedma
Date: Thu May 17 18:52:16 2018
New Revision: 332685
URL: http://llvm.org/viewvc/llvm-project?rev=332685&view=rev
Log:
[MachineOutliner] Count savings from outlining in bytes.
Counting the number of instructions is both unintuitive and inaccurate.
On AArch64, this only affects the generated remarks and certain rare
pseudo-instructions, but it will have a bigger impact on other targets.
Differential Revision: https://reviews.llvm.org/D46921
Modified:
llvm/trunk/include/llvm/CodeGen/TargetInstrInfo.h
llvm/trunk/lib/CodeGen/MachineOutliner.cpp
llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp
llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
llvm/trunk/test/CodeGen/AArch64/machine-outliner-remarks.ll
Modified: llvm/trunk/include/llvm/CodeGen/TargetInstrInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/TargetInstrInfo.h?rev=332685&r1=332684&r2=332685&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/TargetInstrInfo.h (original)
+++ llvm/trunk/include/llvm/CodeGen/TargetInstrInfo.h Thu May 17 18:52:16 2018
@@ -1598,6 +1598,10 @@ public:
/// Describes the number of instructions that it will take to call and
/// construct a frame for a given outlining candidate.
struct MachineOutlinerInfo {
+ /// Represents the size of a sequence in bytes. (Some instructions vary
+ /// widely in size, so just counting the instructions isn't very useful.)
+ unsigned SequenceSize;
+
/// Number of instructions to call an outlined function for this candidate.
unsigned CallOverhead;
@@ -1614,10 +1618,11 @@ public:
unsigned FrameConstructionID;
MachineOutlinerInfo() {}
- MachineOutlinerInfo(unsigned CallOverhead, unsigned FrameOverhead,
- unsigned CallConstructionID,
+ MachineOutlinerInfo(unsigned SequenceSize, unsigned CallOverhead,
+ unsigned FrameOverhead, unsigned CallConstructionID,
unsigned FrameConstructionID)
- : CallOverhead(CallOverhead), FrameOverhead(FrameOverhead),
+ : SequenceSize(SequenceSize), CallOverhead(CallOverhead),
+ FrameOverhead(FrameOverhead),
CallConstructionID(CallConstructionID),
FrameConstructionID(FrameConstructionID) {}
};
Modified: llvm/trunk/lib/CodeGen/MachineOutliner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineOutliner.cpp?rev=332685&r1=332684&r2=332685&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineOutliner.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineOutliner.cpp Thu May 17 18:52:16 2018
@@ -210,17 +210,22 @@ public:
return getOccurrenceCount();
}
- /// Return the number of instructions it would take to outline this
+ /// Return the number of bytes it would take to outline this
/// function.
unsigned getOutliningCost() {
- return (OccurrenceCount * MInfo.CallOverhead) + Sequence.size() +
+ return (OccurrenceCount * MInfo.CallOverhead) + MInfo.SequenceSize +
MInfo.FrameOverhead;
}
+ /// Return the size in bytes of the unoutlined sequences.
+ unsigned getNotOutlinedCost() {
+ return OccurrenceCount * MInfo.SequenceSize;
+ }
+
/// Return the number of instructions that would be saved by outlining
/// this function.
unsigned getBenefit() {
- unsigned NotOutlinedCost = OccurrenceCount * Sequence.size();
+ unsigned NotOutlinedCost = getNotOutlinedCost();
unsigned OutlinedCost = getOutliningCost();
return (NotOutlinedCost < OutlinedCost) ? 0
: NotOutlinedCost - OutlinedCost;
@@ -1054,10 +1059,10 @@ unsigned MachineOutliner::findCandidates
R << "Did not outline " << NV("Length", StringLen) << " instructions"
<< " from " << NV("NumOccurrences", RepeatedSequenceLocs.size())
<< " locations."
- << " Instructions from outlining all occurrences ("
+ << " Bytes from outlining all occurrences ("
<< NV("OutliningCost", OF.getOutliningCost()) << ")"
- << " >= Unoutlined instruction count ("
- << NV("NotOutliningCost", StringLen * OF.getOccurrenceCount()) << ")"
+ << " >= Unoutlined instruction bytes ("
+ << NV("NotOutliningCost", OF.getNotOutlinedCost()) << ")"
<< " (Also found at: ";
// Tell the user the other places the candidate was found.
@@ -1378,7 +1383,7 @@ bool MachineOutliner::outline(
MachineOptimizationRemark R(DEBUG_TYPE, "OutlinedFunction",
MBB->findDebugLoc(MBB->begin()), MBB);
R << "Saved " << NV("OutliningBenefit", OF.getBenefit())
- << " instructions by "
+ << " bytes by "
<< "outlining " << NV("Length", OF.Sequence.size()) << " instructions "
<< "from " << NV("NumOccurrences", OF.getOccurrenceCount())
<< " locations. "
Modified: llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp?rev=332685&r1=332684&r2=332685&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64InstrInfo.cpp Thu May 17 18:52:16 2018
@@ -4936,11 +4936,15 @@ AArch64InstrInfo::getOutlininingCandidat
std::vector<
std::pair<MachineBasicBlock::iterator, MachineBasicBlock::iterator>>
&RepeatedSequenceLocs) const {
-
+ unsigned SequenceSize = std::accumulate(
+ RepeatedSequenceLocs[0].first, std::next(RepeatedSequenceLocs[0].second),
+ 0, [this](unsigned Sum, const MachineInstr &MI) {
+ return Sum + getInstSizeInBytes(MI);
+ });
unsigned CallID = MachineOutlinerDefault;
unsigned FrameID = MachineOutlinerDefault;
- unsigned NumInstrsForCall = 3;
- unsigned NumInstrsToCreateFrame = 1;
+ unsigned NumBytesForCall = 12;
+ unsigned NumBytesToCreateFrame = 4;
auto DoesntNeedLRSave =
[this](std::pair<MachineBasicBlock::iterator, MachineBasicBlock::iterator>
@@ -4951,23 +4955,23 @@ AArch64InstrInfo::getOutlininingCandidat
if (RepeatedSequenceLocs[0].second->isTerminator()) {
CallID = MachineOutlinerTailCall;
FrameID = MachineOutlinerTailCall;
- NumInstrsForCall = 1;
- NumInstrsToCreateFrame = 0;
+ NumBytesForCall = 4;
+ NumBytesToCreateFrame = 0;
}
else if (std::all_of(RepeatedSequenceLocs.begin(), RepeatedSequenceLocs.end(),
DoesntNeedLRSave)) {
CallID = MachineOutlinerNoLRSave;
FrameID = MachineOutlinerNoLRSave;
- NumInstrsForCall = 1;
- NumInstrsToCreateFrame = 1;
+ NumBytesForCall = 4;
+ NumBytesToCreateFrame = 4;
}
// Check if the range contains a call. These require a save + restore of the
// link register.
if (std::any_of(RepeatedSequenceLocs[0].first, RepeatedSequenceLocs[0].second,
[](const MachineInstr &MI) { return MI.isCall(); }))
- NumInstrsToCreateFrame += 2; // Save + restore the link register.
+ NumBytesToCreateFrame += 8; // Save + restore the link register.
// Handle the last instruction separately. If this is a tail call, then the
// last instruction is a call. We don't want to save + restore in this case.
@@ -4975,10 +4979,10 @@ AArch64InstrInfo::getOutlininingCandidat
// it being valid to tail call this sequence. We should consider this as well.
else if (RepeatedSequenceLocs[0].second->isCall() &&
FrameID != MachineOutlinerTailCall)
- NumInstrsToCreateFrame += 2;
+ NumBytesToCreateFrame += 8;
- return MachineOutlinerInfo(NumInstrsForCall, NumInstrsToCreateFrame, CallID,
- FrameID);
+ return MachineOutlinerInfo(SequenceSize, NumBytesForCall,
+ NumBytesToCreateFrame, CallID, FrameID);
}
bool AArch64InstrInfo::isFunctionSafeToOutlineFrom(
Modified: llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrInfo.cpp?rev=332685&r1=332684&r2=332685&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86InstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86InstrInfo.cpp Thu May 17 18:52:16 2018
@@ -11134,15 +11134,26 @@ X86InstrInfo::getOutlininingCandidateInf
std::vector<
std::pair<MachineBasicBlock::iterator, MachineBasicBlock::iterator>>
&RepeatedSequenceLocs) const {
+ unsigned SequenceSize = std::accumulate(
+ RepeatedSequenceLocs[0].first, std::next(RepeatedSequenceLocs[0].second),
+ 0, [this](unsigned Sum, const MachineInstr &MI) {
+ // FIXME: x86 doesn't implement getInstSizeInBytes, so we can't
+ // tell the cost. Just assume each instruction is one byte.
+ if (MI.isDebugInstr() || MI.isKill())
+ return Sum;
+ return Sum + 1;
+ });
+ // FIXME: Use real size in bytes for call and ret instructions.
if (RepeatedSequenceLocs[0].second->isTerminator())
- return MachineOutlinerInfo(1, // Number of instructions to emit call.
- 0, // Number of instructions to emit frame.
+ return MachineOutlinerInfo(SequenceSize,
+ 1, // Number of bytes to emit call.
+ 0, // Number of bytes to emit frame.
MachineOutlinerTailCall, // Type of call.
MachineOutlinerTailCall // Type of frame.
);
- return MachineOutlinerInfo(1, 1, MachineOutlinerDefault,
+ return MachineOutlinerInfo(SequenceSize, 1, 1, MachineOutlinerDefault,
MachineOutlinerDefault);
}
Modified: llvm/trunk/test/CodeGen/AArch64/machine-outliner-remarks.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/AArch64/machine-outliner-remarks.ll?rev=332685&r1=332684&r2=332685&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/AArch64/machine-outliner-remarks.ll (original)
+++ llvm/trunk/test/CodeGen/AArch64/machine-outliner-remarks.ll Thu May 17 18:52:16 2018
@@ -1,10 +1,10 @@
; RUN: llc %s -enable-machine-outliner -mtriple=aarch64-unknown-unknown -pass-remarks=machine-outliner -pass-remarks-missed=machine-outliner -o /dev/null 2>&1 | FileCheck %s
; CHECK: machine-outliner-remarks.ll:5:9:
; CHECK-SAME: Did not outline 2 instructions from 2 locations.
-; CHECK-SAME: Instructions from outlining all occurrences (9) >=
-; CHECK-SAME: Unoutlined instruction count (4)
+; CHECK-SAME: Bytes from outlining all occurrences (36) >=
+; CHECK-SAME: Unoutlined instruction bytes (16)
; CHECK-SAME: (Also found at: machine-outliner-remarks.ll:13:9)
-; CHECK: remark: <unknown>:0:0: Saved 5 instructions by outlining 12 instructions
+; CHECK: remark: <unknown>:0:0: Saved 20 bytes by outlining 12 instructions
; CHECK-SAME: from 2 locations. (Found at: machine-outliner-remarks.ll:36:1,
; CHECK-SAME: machine-outliner-remarks.ll:27:9)
; RUN: llc %s -enable-machine-outliner -mtriple=aarch64-unknown-unknown -o /dev/null -pass-remarks-missed=machine-outliner -pass-remarks-output=%t.yaml
@@ -21,11 +21,11 @@
; YAML-NEXT: - String: ' from '
; YAML-NEXT: - NumOccurrences: '2'
; YAML-NEXT: - String: ' locations.'
-; YAML-NEXT: - String: ' Instructions from outlining all occurrences ('
-; YAML-NEXT: - OutliningCost: '9'
+; YAML-NEXT: - String: ' Bytes from outlining all occurrences ('
+; YAML-NEXT: - OutliningCost: '36'
; YAML-NEXT: - String: ')'
-; YAML-NEXT: - String: ' >= Unoutlined instruction count ('
-; YAML-NEXT: - NotOutliningCost: '4'
+; YAML-NEXT: - String: ' >= Unoutlined instruction bytes ('
+; YAML-NEXT: - NotOutliningCost: '16'
; YAML-NEXT: - String: ')'
; YAML-NEXT: - String: ' (Also found at: '
; YAML-NEXT: - OtherStartLoc1: 'machine-outliner-remarks.ll:13:9'
@@ -37,8 +37,8 @@
; YAML-NEXT: Function: OUTLINED_FUNCTION_0
; YAML-NEXT: Args:
; YAML-NEXT: - String: 'Saved '
-; YAML-NEXT: - OutliningBenefit: '5'
-; YAML-NEXT: - String: ' instructions by '
+; YAML-NEXT: - OutliningBenefit: '20'
+; YAML-NEXT: - String: ' bytes by '
; YAML-NEXT: - String: 'outlining '
; YAML-NEXT: - Length: '12'
; YAML-NEXT: - String: ' instructions '
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