Skip to content

[AArch64] Fix FPMR handling when switching streaming mode #135827

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
Lukacma merged 1 commit into from
Apr 16, 2025
Merged

[AArch64] Fix FPMR handling when switching streaming mode #135827

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
3 changes: 3 additions & 0 deletions llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -8880,12 +8880,15 @@ void AArch64TargetLowering::AdjustInstrPostInstrSelection(MachineInstr &MI,
MI.removeOperand(I);

// The SVE vector length can change when entering/leaving streaming mode.
// FPMR is set to 0 when entering/leaving streaming mode.
if (MI.getOperand(0).getImm() == AArch64SVCR::SVCRSM ||
MI.getOperand(0).getImm() == AArch64SVCR::SVCRSMZA) {
MI.addOperand(MachineOperand::CreateReg(AArch64::VG, /*IsDef=*/false,
/*IsImplicit=*/true));
MI.addOperand(MachineOperand::CreateReg(AArch64::VG, /*IsDef=*/true,
/*IsImplicit=*/true));
MI.addOperand(MachineOperand::CreateReg(AArch64::FPMR, /*IsDef=*/true,
/*IsImplicit=*/true));
}
}

Expand Down
23 changes: 23 additions & 0 deletions llvm/test/CodeGen/AArch64/sme-write-fpmr.ll
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
; RUN: llc -mattr=+sme -stop-after=finalize-isel < %s | FileCheck %s

target triple = "aarch64"

; Check that we don't define FPMR for 'smstart za' and 'smstop za'
define void @smstart_za() "aarch64_new_za" nounwind {
; CHECK-LABEL: name: smstart_za
; CHECK-NOT: implicit-def {{[^,]*}}$fpmr
ret void
}

; Check that we do define FPMR for 'smstart sm' and 'smstop sm'
define void @smstart_sm() nounwind {
; CHECK-LABEL: name: smstart_sm
; CHECK: MSRpstatesvcrImm1 1, 1,
; CHECK-SAME: implicit-def {{[^,]*}}$fpmr
; CHECK: MSRpstatesvcrImm1 1, 0,
; CHECK-SAME: implicit-def {{[^,]*}}$fpmr
call void @require_sm()
ret void
}

declare void @require_sm() "aarch64_pstate_sm_enabled"
Loading