[llvm] [CodeGen] Check entire block if no threshold was given for liveliness (PR #83526)
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Fri Mar 1 06:37:42 PST 2024
https://github.com/AtariDreams updated https://github.com/llvm/llvm-project/pull/83526
>From 5001c1fc06e72fb92b7821f437086a1de7a6b05c Mon Sep 17 00:00:00 2001
From: Rose <83477269+AtariDreams at users.noreply.github.com>
Date: Fri, 1 Mar 2024 00:19:21 -0500
Subject: [PATCH] [CodeGen] Check entire block if no threshold was given for
liveliness
We could pass MBB.size(), but we should compute liveness the correct way if we have the entire block.
---
llvm/include/llvm/CodeGen/MachineBasicBlock.h | 5 +++-
llvm/lib/CodeGen/MachineBasicBlock.cpp | 30 +++++++++++++++++--
llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp | 6 ++--
llvm/lib/Target/X86/X86FixupLEAs.cpp | 4 +--
4 files changed, 37 insertions(+), 8 deletions(-)
diff --git a/llvm/include/llvm/CodeGen/MachineBasicBlock.h b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
index dc2035fa598c46..05fa92304cbfbb 100644
--- a/llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -1147,10 +1147,13 @@ class MachineBasicBlock
/// after (searching just for defs) \p Before.
///
/// \p Reg must be a physical register.
+ LivenessQueryResult computeRegisterLiveness(const TargetRegisterInfo *TRI,
+ MCRegister Reg,
+ const_iterator Before) const;
LivenessQueryResult computeRegisterLiveness(const TargetRegisterInfo *TRI,
MCRegister Reg,
const_iterator Before,
- unsigned Neighborhood = 10) const;
+ unsigned Neighborhood) const;
// Debugging methods.
void dump() const;
diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 4410fb7ecd23b6..efddd27ab2ce6b 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -1598,15 +1598,42 @@ MachineBasicBlock::getProbabilityIterator(MachineBasicBlock::succ_iterator I) {
return Probs.begin() + index;
}
+MachineBasicBlock::LivenessQueryResult
+MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI,
+ MCRegister Reg,
+ const_iterator Before) const {
+ LivePhysRegs UsedRegs(*TRI);
+ UsedRegs.addLiveOuts(*this);
+
+ const MachineFunction *MF = getParent();
+ const MCPhysReg *CSRegs = TRI->getCalleeSavedRegs(MF);
+ for (unsigned i = 0; CSRegs[i]; ++i)
+ UsedRegs.addReg(CSRegs[i]);
+
+ auto InstUpToBefore = end();
+
+ while (InstUpToBefore != Before)
+ // The pre-decrement is on purpose here.
+ // We want to have the liveness right before Before.
+ UsedRegs.stepBackward(*--InstUpToBefore);
+
+ if (UsedRegs.available(MF->getRegInfo(), Reg))
+ return LQR_Dead;
+
+ return LQR_Live;
+}
+
/// Return whether (physical) register "Reg" has been <def>ined and not <kill>ed
/// as of just before "MI".
///
/// Search is localised to a neighborhood of
/// Neighborhood instructions before (searching for defs or kills) and N
/// instructions after (searching just for defs) MI.
+
MachineBasicBlock::LivenessQueryResult
MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI,
- MCRegister Reg, const_iterator Before,
+ MCRegister Reg,
+ const_iterator Before,
unsigned Neighborhood) const {
unsigned N = Neighborhood;
@@ -1641,7 +1668,6 @@ MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI,
return LQR_Dead;
}
-
N = Neighborhood;
// Start by searching backwards from Before, looking for kills, reads or defs.
diff --git a/llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp b/llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
index 6121055eb02176..1f5fbf178e51c0 100644
--- a/llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
+++ b/llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
@@ -635,9 +635,9 @@ MachineInstr *ARMLoadStoreOpt::CreateLoadStoreMulti(
// For Thumb1 targets, it might be necessary to clobber the CPSR to merge.
// Compute liveness information for that register to make the decision.
- bool SafeToClobberCPSR = !isThumb1 ||
- (MBB.computeRegisterLiveness(TRI, ARM::CPSR, InsertBefore, 20) ==
- MachineBasicBlock::LQR_Dead);
+ bool SafeToClobberCPSR =
+ !isThumb1 || (MBB.computeRegisterLiveness(TRI, ARM::CPSR, InsertBefore) ==
+ MachineBasicBlock::LQR_Dead);
bool Writeback = isThumb1; // Thumb1 LDM/STM have base reg writeback.
diff --git a/llvm/lib/Target/X86/X86FixupLEAs.cpp b/llvm/lib/Target/X86/X86FixupLEAs.cpp
index beeebf42dfe81a..446754a6815f8d 100644
--- a/llvm/lib/Target/X86/X86FixupLEAs.cpp
+++ b/llvm/lib/Target/X86/X86FixupLEAs.cpp
@@ -698,7 +698,7 @@ void FixupLEAPass::processInstructionForSlowLEA(MachineBasicBlock::iterator &I,
const MachineOperand &Segment = MI.getOperand(1 + X86::AddrSegmentReg);
if (Segment.getReg() != 0 || !Offset.isImm() ||
- MBB.computeRegisterLiveness(TRI, X86::EFLAGS, I, 4) !=
+ MBB.computeRegisterLiveness(TRI, X86::EFLAGS, I) !=
MachineBasicBlock::LQR_Dead)
return;
const Register DstR = Dst.getReg();
@@ -750,7 +750,7 @@ void FixupLEAPass::processInstrForSlow3OpLEA(MachineBasicBlock::iterator &I,
const MachineOperand &Segment = MI.getOperand(1 + X86::AddrSegmentReg);
if (!(TII->isThreeOperandsLEA(MI) || hasInefficientLEABaseReg(Base, Index)) ||
- MBB.computeRegisterLiveness(TRI, X86::EFLAGS, I, 4) !=
+ MBB.computeRegisterLiveness(TRI, X86::EFLAGS, I) !=
MachineBasicBlock::LQR_Dead ||
Segment.getReg() != X86::NoRegister)
return;
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