[llvm] [LiveIns] Improve recomputeLiveIns() (PR #88951)
Kai Nacke via llvm-commits
llvm-commits at lists.llvm.org
Wed Apr 17 12:35:55 PDT 2024
https://github.com/redstar updated https://github.com/llvm/llvm-project/pull/88951
>From c23821dda7f7158a4114cf4ad3bb1a4370f7944a Mon Sep 17 00:00:00 2001
From: Kai Nacke <kai.peter.nacke at ibm.com>
Date: Tue, 16 Apr 2024 10:52:23 -0400
Subject: [PATCH 1/4] [LiveIns] Improve recomputeLiveIns()
Some small changes to recomputeLiveIns() to improve performance:
- Instead of copying the list of old live-ins, and then clearing
them, a new method swaps the list for an empty one.
- getLiveIns() now returns a constant reference to the list
As result, the list-data is never copied. Depending on the implementation
details of the vector container, it can also save calls to allocate
and deallocate memory.
I see a small improvement on CTMark with these changes.
---
llvm/include/llvm/CodeGen/LivePhysRegs.h | 10 +++++-----
llvm/include/llvm/CodeGen/MachineBasicBlock.h | 6 +++++-
llvm/lib/CodeGen/MachineBasicBlock.cpp | 5 +++++
3 files changed, 15 insertions(+), 6 deletions(-)
diff --git a/llvm/include/llvm/CodeGen/LivePhysRegs.h b/llvm/include/llvm/CodeGen/LivePhysRegs.h
index 9574a6f0c7c005..3782fce46f7d23 100644
--- a/llvm/include/llvm/CodeGen/LivePhysRegs.h
+++ b/llvm/include/llvm/CodeGen/LivePhysRegs.h
@@ -197,16 +197,16 @@ void computeAndAddLiveIns(LivePhysRegs &LiveRegs,
/// Convenience function for recomputing live-in's for a MBB. Returns true if
/// any changes were made.
-static inline bool recomputeLiveIns(MachineBasicBlock &MBB) {
+inline bool recomputeLiveIns(MachineBasicBlock &MBB) {
LivePhysRegs LPR;
- auto oldLiveIns = MBB.getLiveIns();
+ std::vector<MachineBasicBlock::RegisterMaskPair> OldLiveIns;
- MBB.clearLiveIns();
+ MBB.clearLiveIns(OldLiveIns);
computeAndAddLiveIns(LPR, MBB);
MBB.sortUniqueLiveIns();
- auto newLiveIns = MBB.getLiveIns();
- return oldLiveIns != newLiveIns;
+ auto NewLiveIns = MBB.getLiveIns();
+ return OldLiveIns != NewLiveIns;
}
/// Convenience function for recomputing live-in's for a set of MBBs until the
diff --git a/llvm/include/llvm/CodeGen/MachineBasicBlock.h b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
index dc2035fa598c46..8074c9504762a5 100644
--- a/llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -441,6 +441,10 @@ class MachineBasicBlock
/// Clear live in list.
void clearLiveIns();
+ /// Clear the live in list, and return the removed live in's in \p OldLiveIns.
+ /// Requires that the vector \p OldLiveIns is empty.
+ void clearLiveIns(std::vector<RegisterMaskPair> &OldLiveIns);
+
/// Add PhysReg as live in to this block, and ensure that there is a copy of
/// PhysReg to a virtual register of class RC. Return the virtual register
/// that is a copy of the live in PhysReg.
@@ -477,7 +481,7 @@ class MachineBasicBlock
/// Remove entry from the livein set and return iterator to the next.
livein_iterator removeLiveIn(livein_iterator I);
- std::vector<RegisterMaskPair> getLiveIns() const { return LiveIns; }
+ const std::vector<RegisterMaskPair> getLiveIns() const { return LiveIns; }
class liveout_iterator {
public:
diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index b2114c250ac09d..18e3815a72b1c3 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -1728,6 +1728,11 @@ void MachineBasicBlock::clearLiveIns() {
LiveIns.clear();
}
+void MachineBasicBlock::clearLiveIns(std::vector<RegisterMaskPair> &OldLiveIns) {
+ assert(OldLiveIns.empty() && "Vector must be empty");
+ std::swap(LiveIns, OldLiveIns);
+}
+
MachineBasicBlock::livein_iterator MachineBasicBlock::livein_begin() const {
assert(getParent()->getProperties().hasProperty(
MachineFunctionProperties::Property::TracksLiveness) &&
>From d8919915abb0b8d0743aca3490c444134dafe2b8 Mon Sep 17 00:00:00 2001
From: Kai Nacke <kai at redstar.de>
Date: Wed, 17 Apr 2024 14:50:17 -0400
Subject: [PATCH 2/4] Update llvm/include/llvm/CodeGen/MachineBasicBlock.h
Co-authored-by: Nikita Popov <github at npopov.com>
---
llvm/include/llvm/CodeGen/MachineBasicBlock.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/include/llvm/CodeGen/MachineBasicBlock.h b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
index 8074c9504762a5..5b6be3a96b2fb3 100644
--- a/llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -481,7 +481,7 @@ class MachineBasicBlock
/// Remove entry from the livein set and return iterator to the next.
livein_iterator removeLiveIn(livein_iterator I);
- const std::vector<RegisterMaskPair> getLiveIns() const { return LiveIns; }
+ const std::vector<RegisterMaskPair> &getLiveIns() const { return LiveIns; }
class liveout_iterator {
public:
>From 3180bc706f8cdad2a1d7d55660954cb21e3bcd18 Mon Sep 17 00:00:00 2001
From: Kai Nacke <kai.peter.nacke at ibm.com>
Date: Wed, 17 Apr 2024 15:17:19 -0400
Subject: [PATCH 3/4] Update based on review comments.
---
llvm/include/llvm/CodeGen/LivePhysRegs.h | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/llvm/include/llvm/CodeGen/LivePhysRegs.h b/llvm/include/llvm/CodeGen/LivePhysRegs.h
index 3782fce46f7d23..d315e4ff6f3abe 100644
--- a/llvm/include/llvm/CodeGen/LivePhysRegs.h
+++ b/llvm/include/llvm/CodeGen/LivePhysRegs.h
@@ -197,7 +197,7 @@ void computeAndAddLiveIns(LivePhysRegs &LiveRegs,
/// Convenience function for recomputing live-in's for a MBB. Returns true if
/// any changes were made.
-inline bool recomputeLiveIns(MachineBasicBlock &MBB) {
+static inline bool recomputeLiveIns(MachineBasicBlock &MBB) {
LivePhysRegs LPR;
std::vector<MachineBasicBlock::RegisterMaskPair> OldLiveIns;
@@ -205,7 +205,8 @@ inline bool recomputeLiveIns(MachineBasicBlock &MBB) {
computeAndAddLiveIns(LPR, MBB);
MBB.sortUniqueLiveIns();
- auto NewLiveIns = MBB.getLiveIns();
+ const std::vector<MachineBasicBlock::RegisterMaskPair> &NewLiveIns =
+ MBB.getLiveIns();
return OldLiveIns != NewLiveIns;
}
>From 82071412943dbf296ae464b4af6344910fd153f6 Mon Sep 17 00:00:00 2001
From: Kai Nacke <kai.peter.nacke at ibm.com>
Date: Wed, 17 Apr 2024 15:35:33 -0400
Subject: [PATCH 4/4] Fix formatting
---
llvm/lib/CodeGen/MachineBasicBlock.cpp | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 18e3815a72b1c3..0bd5f09564ec0c 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -1728,7 +1728,8 @@ void MachineBasicBlock::clearLiveIns() {
LiveIns.clear();
}
-void MachineBasicBlock::clearLiveIns(std::vector<RegisterMaskPair> &OldLiveIns) {
+void MachineBasicBlock::clearLiveIns(
+ std::vector<RegisterMaskPair> &OldLiveIns) {
assert(OldLiveIns.empty() && "Vector must be empty");
std::swap(LiveIns, OldLiveIns);
}
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