release/21.x: [LoongArch] Add isSafeToMove hook to prevent unsafe instruction motion (#163725)#166936
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dyung merged 1 commit intollvm:release/21.xfrom Nov 13, 2025
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@OCHyams What do you think about merging this PR to the release branch? |
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@llvm/pr-subscribers-backend-loongarch Author: None (llvmbot) ChangesBackport cdc3cb2 Requested by: @llvmbot Full diff: https://github.com/llvm/llvm-project/pull/166936.diff 4 Files Affected:
diff --git a/llvm/include/llvm/CodeGen/TargetInstrInfo.h b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
index b5b83c7ff1164..4d6e34bf4e3a1 100644
--- a/llvm/include/llvm/CodeGen/TargetInstrInfo.h
+++ b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
@@ -1730,6 +1730,17 @@ class LLVM_ABI TargetInstrInfo : public MCInstrInfo {
return true;
}
+ /// Return true if it's safe to move a machine instruction.
+ /// This allows the backend to prevent certain special instruction
+ /// sequences from being broken by instruction motion in optimization
+ /// passes.
+ /// By default, this returns true for every instruction.
+ virtual bool isSafeToMove(const MachineInstr &MI,
+ const MachineBasicBlock *MBB,
+ const MachineFunction &MF) const {
+ return true;
+ }
+
/// Test if the given instruction should be considered a scheduling boundary.
/// This primarily includes labels and terminators.
virtual bool isSchedulingBoundary(const MachineInstr &MI,
diff --git a/llvm/lib/CodeGen/BranchFolding.cpp b/llvm/lib/CodeGen/BranchFolding.cpp
index 3b3e7a418feb5..2886a1b7c9e02 100644
--- a/llvm/lib/CodeGen/BranchFolding.cpp
+++ b/llvm/lib/CodeGen/BranchFolding.cpp
@@ -1971,6 +1971,7 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
MachineBasicBlock::iterator FIB = FBB->begin();
MachineBasicBlock::iterator TIE = TBB->end();
MachineBasicBlock::iterator FIE = FBB->end();
+ MachineFunction &MF = *MBB->getParent();
while (TIB != TIE && FIB != FIE) {
// Skip dbg_value instructions. These do not count.
TIB = skipDebugInstructionsForward(TIB, TIE, false);
@@ -1985,6 +1986,10 @@ bool BranchFolder::HoistCommonCodeInSuccs(MachineBasicBlock *MBB) {
// Hard to reason about register liveness with predicated instruction.
break;
+ if (!TII->isSafeToMove(*TIB, MBB, MF))
+ // Don't hoist the instruction if it isn't safe to move.
+ break;
+
bool IsSafe = true;
for (MachineOperand &MO : TIB->operands()) {
// Don't attempt to hoist instructions with register masks.
diff --git a/llvm/lib/Target/LoongArch/LoongArchInstrInfo.cpp b/llvm/lib/Target/LoongArch/LoongArchInstrInfo.cpp
index 26d36f1c5058f..75a230268bf58 100644
--- a/llvm/lib/Target/LoongArch/LoongArchInstrInfo.cpp
+++ b/llvm/lib/Target/LoongArch/LoongArchInstrInfo.cpp
@@ -378,12 +378,9 @@ bool LoongArchInstrInfo::isBranchOffsetInRange(unsigned BranchOp,
}
}
-bool LoongArchInstrInfo::isSchedulingBoundary(const MachineInstr &MI,
- const MachineBasicBlock *MBB,
- const MachineFunction &MF) const {
- if (TargetInstrInfo::isSchedulingBoundary(MI, MBB, MF))
- return true;
-
+bool LoongArchInstrInfo::isSafeToMove(const MachineInstr &MI,
+ const MachineBasicBlock *MBB,
+ const MachineFunction &MF) const {
auto MII = MI.getIterator();
auto MIE = MBB->end();
@@ -429,25 +426,25 @@ bool LoongArchInstrInfo::isSchedulingBoundary(const MachineInstr &MI,
auto MO2 = Lu32I->getOperand(2).getTargetFlags();
if (MO0 == LoongArchII::MO_PCREL_HI && MO1 == LoongArchII::MO_PCREL_LO &&
MO2 == LoongArchII::MO_PCREL64_LO)
- return true;
+ return false;
if ((MO0 == LoongArchII::MO_GOT_PC_HI || MO0 == LoongArchII::MO_LD_PC_HI ||
MO0 == LoongArchII::MO_GD_PC_HI) &&
MO1 == LoongArchII::MO_GOT_PC_LO && MO2 == LoongArchII::MO_GOT_PC64_LO)
- return true;
+ return false;
if (MO0 == LoongArchII::MO_IE_PC_HI && MO1 == LoongArchII::MO_IE_PC_LO &&
MO2 == LoongArchII::MO_IE_PC64_LO)
- return true;
+ return false;
if (MO0 == LoongArchII::MO_DESC_PC_HI &&
MO1 == LoongArchII::MO_DESC_PC_LO &&
MO2 == LoongArchII::MO_DESC64_PC_LO)
- return true;
+ return false;
break;
}
case LoongArch::LU52I_D: {
auto MO = MI.getOperand(2).getTargetFlags();
if (MO == LoongArchII::MO_PCREL64_HI || MO == LoongArchII::MO_GOT_PC64_HI ||
MO == LoongArchII::MO_IE_PC64_HI || MO == LoongArchII::MO_DESC64_PC_HI)
- return true;
+ return false;
break;
}
default:
@@ -487,7 +484,7 @@ bool LoongArchInstrInfo::isSchedulingBoundary(const MachineInstr &MI,
auto MO1 = LoongArchII::getDirectFlags(SecondOp->getOperand(2));
auto MO2 = LoongArchII::getDirectFlags(Ld->getOperand(2));
if (MO1 == LoongArchII::MO_DESC_PC_LO && MO2 == LoongArchII::MO_DESC_LD)
- return true;
+ return false;
break;
}
if (SecondOp == MIE ||
@@ -496,34 +493,34 @@ bool LoongArchInstrInfo::isSchedulingBoundary(const MachineInstr &MI,
auto MO1 = LoongArchII::getDirectFlags(SecondOp->getOperand(2));
if (MO0 == LoongArchII::MO_PCREL_HI && SecondOp->getOpcode() == AddiOp &&
MO1 == LoongArchII::MO_PCREL_LO)
- return true;
+ return false;
if (MO0 == LoongArchII::MO_GOT_PC_HI && SecondOp->getOpcode() == LdOp &&
MO1 == LoongArchII::MO_GOT_PC_LO)
- return true;
+ return false;
if ((MO0 == LoongArchII::MO_LD_PC_HI ||
MO0 == LoongArchII::MO_GD_PC_HI) &&
SecondOp->getOpcode() == AddiOp && MO1 == LoongArchII::MO_GOT_PC_LO)
- return true;
+ return false;
break;
}
case LoongArch::ADDI_W:
case LoongArch::ADDI_D: {
auto MO = LoongArchII::getDirectFlags(MI.getOperand(2));
if (MO == LoongArchII::MO_PCREL_LO || MO == LoongArchII::MO_GOT_PC_LO)
- return true;
+ return false;
break;
}
case LoongArch::LD_W:
case LoongArch::LD_D: {
auto MO = LoongArchII::getDirectFlags(MI.getOperand(2));
if (MO == LoongArchII::MO_GOT_PC_LO)
- return true;
+ return false;
break;
}
case LoongArch::PseudoDESC_CALL: {
auto MO = LoongArchII::getDirectFlags(MI.getOperand(2));
if (MO == LoongArchII::MO_DESC_CALL)
- return true;
+ return false;
break;
}
default:
@@ -531,6 +528,18 @@ bool LoongArchInstrInfo::isSchedulingBoundary(const MachineInstr &MI,
}
}
+ return true;
+}
+
+bool LoongArchInstrInfo::isSchedulingBoundary(const MachineInstr &MI,
+ const MachineBasicBlock *MBB,
+ const MachineFunction &MF) const {
+ if (TargetInstrInfo::isSchedulingBoundary(MI, MBB, MF))
+ return true;
+
+ if (!isSafeToMove(MI, MBB, MF))
+ return true;
+
return false;
}
diff --git a/llvm/lib/Target/LoongArch/LoongArchInstrInfo.h b/llvm/lib/Target/LoongArch/LoongArchInstrInfo.h
index 63b7112b8b40a..282ea30b03299 100644
--- a/llvm/lib/Target/LoongArch/LoongArchInstrInfo.h
+++ b/llvm/lib/Target/LoongArch/LoongArchInstrInfo.h
@@ -64,6 +64,9 @@ class LoongArchInstrInfo : public LoongArchGenInstrInfo {
bool isBranchOffsetInRange(unsigned BranchOpc,
int64_t BrOffset) const override;
+ bool isSafeToMove(const MachineInstr &MI, const MachineBasicBlock *MBB,
+ const MachineFunction &MF) const override;
+
bool isSchedulingBoundary(const MachineInstr &MI,
const MachineBasicBlock *MBB,
const MachineFunction &MF) const override;
|
Contributor
One of the other reviewers is likely better placed to comment here - cc @wangleiat @zhaoqi5 @SixWeining, please could you take a look |
Collaborator
|
Hi @heiher, we are currently only accepting potential patches for the 21.x release branch that fix regressions from a prior release or are major bugs. This does not seem to be either to me, but can you help me to understand whether this meets either for possible inclusion? |
Member
|
The title may not look like a fix, but it actually resolves a regression issue. Also, the mainline patch is being re-landed, and I’ll update this PR once that’s done. Thanks! |
Collaborator
When was this regression introduced? |
Member
|
…tion motion" (llvm#167465) This patch introduces a new virtual method `TargetInstrInfo::isSafeToMove()` to allow backends to control whether a machine instruction can be safely moved by optimization passes. The `BranchFolder` pass now respects this hook when hoisting common code. By default, all instructions are considered safe to to move. For LoongArch, `isSafeToMove()` is overridden to prevent relocation-related instruction sequences (e.g. PC-relative addressing and calls) from being broken by instruction motion. Correspondingly, `isSchedulingBoundary()` is updated to reuse this logic for consistency. Relands llvm#163725 (cherry picked from commit ea10026)
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Collaborator
Thanks for the clarification! |
|
@llvmbot (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR. |
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Backport ea10026
Requested by: @llvmbot