[llvm] [AArch64] Fix stack probing clobbering flags (PR #81879)
Momchil Velikov via llvm-commits
llvm-commits at lists.llvm.org
Tue Feb 20 05:27:41 PST 2024
https://github.com/momchil-velikov updated https://github.com/llvm/llvm-project/pull/81879
>From 965cec4603efbaa1296e6ed2236f65df4f929f43 Mon Sep 17 00:00:00 2001
From: Momchil Velikov <momchil.velikov at arm.com>
Date: Thu, 15 Feb 2024 17:11:05 +0000
Subject: [PATCH 1/2] [AArch64] Fix stack probing clobbering flags
Certain stack probing sequences might clobber flags, then we can't use a
block as a prologue if the flags register is a live-in on entry to that
block.
---
.../Target/AArch64/AArch64FrameLowering.cpp | 5 +
.../AArch64/stack-probing-shrink-wrap.mir | 107 ++++++++++++++++++
2 files changed, 112 insertions(+)
create mode 100644 llvm/test/CodeGen/AArch64/stack-probing-shrink-wrap.mir
diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
index 0e9adde564b3e5..c62e750a9b07b0 100644
--- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -1061,6 +1061,11 @@ bool AArch64FrameLowering::canUseAsPrologue(
return false;
}
+ // Certain stack probing sequences might clobber flags, then we can't use
+ // the block as a prologue if the flags register is a live-in.
+ if (TLI->hasInlineStackProbe(*MF) && MBB.isLiveIn(AArch64::NZCV))
+ return false;
+
// Don't need a scratch register if we're not going to re-align the stack or
// emit stack probes.
if (!RegInfo->hasStackRealignment(*MF) && !TLI->hasInlineStackProbe(*MF))
diff --git a/llvm/test/CodeGen/AArch64/stack-probing-shrink-wrap.mir b/llvm/test/CodeGen/AArch64/stack-probing-shrink-wrap.mir
new file mode 100644
index 00000000000000..83aa90d389a4a2
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/stack-probing-shrink-wrap.mir
@@ -0,0 +1,107 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 4
+# RUN: llc %s --start-before=shrink-wrap --stop-after=prologepilog -o - | FileCheck %s
+--- |
+ target triple = "aarch64-linux"
+
+ define void @f(i32 %n) #0 {
+ entry:
+ %a = alloca i8, i32 150000, align 8
+ %c0 = icmp sle i32 %n, 1
+ br i1 %c0, label %if.then1, label %exit
+
+ if.then1: ; preds = %entry
+ %0 = icmp sle i32 %n, 1
+ %v = select i1 %0, i32 0, i32 1
+ call void @g(ptr %a, i32 %v)
+ br label %exit
+
+ exit: ; preds = %if.then1, %entry
+ ret void
+ }
+
+ declare void @g(...)
+
+ attributes #0 = { nounwind "probe-stack"="inline-asm" "stack-probe-size"="4096" }
+
+...
+---
+name: f
+alignment: 4
+tracksRegLiveness: true
+liveins:
+ - { reg: '$w0', virtual-reg: '' }
+frameInfo:
+ localFrameSize: 150000
+stack:
+ - { id: 0, name: a, type: default, offset: 0, size: 150000, alignment: 8,
+ stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+ local-offset: -150000, debug-info-variable: '', debug-info-expression: '',
+ debug-info-location: '' }
+entry_values: []
+callSites: []
+debugValueSubstitutions: []
+constants: []
+machineFunctionInfo: {}
+body: |
+ ; CHECK-LABEL: name: f
+ ; CHECK: bb.0.entry:
+ ; CHECK-NEXT: successors: %bb.3(0x80000000)
+ ; CHECK-NEXT: liveins: $w0, $lr
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: early-clobber $sp = frame-setup STPXpre killed $fp, killed $lr, $sp, -2 :: (store (s64) into %stack.2), (store (s64) into %stack.1)
+ ; CHECK-NEXT: $x9 = frame-setup SUBXri $sp, 36, 12
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.3.entry:
+ ; CHECK-NEXT: successors: %bb.4(0x40000000), %bb.3(0x40000000)
+ ; CHECK-NEXT: liveins: $w0, $x9
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: $sp = frame-setup SUBXri $sp, 1, 12
+ ; CHECK-NEXT: frame-setup STRXui $xzr, $sp, 0
+ ; CHECK-NEXT: $xzr = frame-setup SUBSXrx64 $sp, $x9, 24, implicit-def $nzcv
+ ; CHECK-NEXT: frame-setup Bcc 1, %bb.3, implicit $nzcv
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.4.entry:
+ ; CHECK-NEXT: successors: %bb.1(0x40000000), %bb.2(0x40000000)
+ ; CHECK-NEXT: liveins: $w0
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: $sp = frame-setup SUBXri $sp, 2544, 0
+ ; CHECK-NEXT: frame-setup STRXui $xzr, $sp, 0
+ ; CHECK-NEXT: dead $wzr = SUBSWri killed renamable $w0, 1, 0, implicit-def $nzcv
+ ; CHECK-NEXT: Bcc 12, %bb.2, implicit $nzcv
+ ; CHECK-NEXT: B %bb.1
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.1.if.then1:
+ ; CHECK-NEXT: successors: %bb.2(0x80000000)
+ ; CHECK-NEXT: liveins: $nzcv
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: renamable $w1 = CSINCWr $wzr, $wzr, 13, implicit killed $nzcv
+ ; CHECK-NEXT: $x0 = ADDXri $sp, 0, 0
+ ; CHECK-NEXT: BL @g, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit $x0, implicit $w1, implicit-def $sp
+ ; CHECK-NEXT: {{ $}}
+ ; CHECK-NEXT: bb.2.exit:
+ ; CHECK-NEXT: $sp = frame-destroy ADDXri $sp, 36, 12
+ ; CHECK-NEXT: $sp = frame-destroy ADDXri $sp, 2544, 0
+ ; CHECK-NEXT: early-clobber $sp, $fp, $lr = frame-destroy LDPXpost $sp, 2 :: (load (s64) from %stack.2), (load (s64) from %stack.1)
+ ; CHECK-NEXT: RET_ReallyLR
+ bb.0.entry:
+ successors: %bb.1(0x40000000), %bb.2(0x40000000)
+ liveins: $w0
+
+ dead $wzr = SUBSWri killed renamable $w0, 1, 0, implicit-def $nzcv
+ Bcc 12, %bb.2, implicit $nzcv
+ B %bb.1
+
+ bb.1.if.then1:
+ successors: %bb.2(0x80000000)
+ liveins: $nzcv
+
+ renamable $w1 = CSINCWr $wzr, $wzr, 13, implicit killed $nzcv
+ ADJCALLSTACKDOWN 0, 0, implicit-def dead $sp, implicit $sp
+ $x0 = ADDXri %stack.0.a, 0, 0
+ BL @g, csr_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit $x0, implicit $w1, implicit-def $sp
+ ADJCALLSTACKUP 0, 0, implicit-def dead $sp, implicit $sp
+
+ bb.2.exit:
+ RET_ReallyLR
+
+...
>From 21dae48d45f88ec8fe225cfcf6b08489a1d2c58c Mon Sep 17 00:00:00 2001
From: Momchil Velikov <momchil.velikov at arm.com>
Date: Tue, 20 Feb 2024 13:19:00 +0000
Subject: [PATCH 2/2] [fixup] Use `hasStackProbing`
The difference now is that the condition would trigger
for Windows, where stack probing does clobber flags.
---
llvm/lib/Target/AArch64/AArch64FrameLowering.cpp | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
index c62e750a9b07b0..31b1661e73e363 100644
--- a/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -1063,7 +1063,8 @@ bool AArch64FrameLowering::canUseAsPrologue(
// Certain stack probing sequences might clobber flags, then we can't use
// the block as a prologue if the flags register is a live-in.
- if (TLI->hasInlineStackProbe(*MF) && MBB.isLiveIn(AArch64::NZCV))
+ if (MF->getInfo<AArch64FunctionInfo>()->hasStackProbing() &&
+ MBB.isLiveIn(AArch64::NZCV))
return false;
// Don't need a scratch register if we're not going to re-align the stack or
More information about the llvm-commits
mailing list