[llvm] [CodeGen] Parse frame-pointer attribute once when creating MachineFunction (PR #191974)
Cullen Rhodes via llvm-commits
llvm-commits at lists.llvm.org
Fri Apr 17 03:57:15 PDT 2026
https://github.com/c-rhodes updated https://github.com/llvm/llvm-project/pull/191974
>From 056e2230eca86d1362452178012fb33aeb806362 Mon Sep 17 00:00:00 2001
From: Cullen Rhodes <cullen.rhodes at arm.com>
Date: Mon, 13 Apr 2026 10:13:19 +0000
Subject: [PATCH 1/3] [CodeGen] Parse frame-pointer attribute once when
creating MachineFunction
TargetOptions::DisableFramePointerElim is hot and showing up in
compile-time profiles via AArch64FrameLowering::hasFPImpl on
aarch64-O0-g builds. Repeatedly looking up the function attribute is
expensive. Parsing it once at MachineFunction initialisation and storing
as FramePointerKind on MachineFrameInfo is a -0.21% geomean improvement
on CTMark stage1-aarch64-O0-g. Also helps debug builds on other targets.
https://llvm-compile-time-tracker.com/compare.php?from=215f35eb8f1c313ac135ad47db1cc0b99b3ae694&to=51f6617517177bea1cc49baeab3acaf62d5e9df9&stat=instructions%3Au
---
llvm/include/llvm/CodeGen/MachineFrameInfo.h | 10 ++++++
llvm/lib/CodeGen/MachineFunction.cpp | 17 +++++++++
llvm/lib/CodeGen/TargetOptionsImpl.cpp | 37 ++++++++++----------
3 files changed, 46 insertions(+), 18 deletions(-)
diff --git a/llvm/include/llvm/CodeGen/MachineFrameInfo.h b/llvm/include/llvm/CodeGen/MachineFrameInfo.h
index c4852f84be352..22729e736fbd3 100644
--- a/llvm/include/llvm/CodeGen/MachineFrameInfo.h
+++ b/llvm/include/llvm/CodeGen/MachineFrameInfo.h
@@ -17,6 +17,7 @@
#include "llvm/CodeGen/Register.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
#include "llvm/Support/Alignment.h"
+#include "llvm/Support/CodeGen.h"
#include "llvm/Support/Compiler.h"
#include <cassert>
#include <vector>
@@ -279,6 +280,10 @@ class MachineFrameInfo {
/// Set to true if this function has any function calls.
bool HasCalls = false;
+ /// Frame-pointer policy for this function to avoid repeated attribute
+ /// lookups in hot paths.
+ FramePointerKind FramePointerPolicy = FramePointerKind::None;
+
/// The frame index for the stack protector.
int StackProtectorIdx = -1;
@@ -641,6 +646,11 @@ class MachineFrameInfo {
bool hasCalls() const { return HasCalls; }
void setHasCalls(bool V) { HasCalls = V; }
+ FramePointerKind getFramePointerPolicy() const { return FramePointerPolicy; }
+ void setFramePointerPolicy(FramePointerKind Kind) {
+ FramePointerPolicy = Kind;
+ }
+
/// Returns true if the function contains opaque dynamic stack adjustments.
bool hasOpaqueSPAdjustment() const { return HasOpaqueSPAdjustment; }
void setHasOpaqueSPAdjustment(bool B) { HasOpaqueSPAdjustment = B; }
diff --git a/llvm/lib/CodeGen/MachineFunction.cpp b/llvm/lib/CodeGen/MachineFunction.cpp
index a2dd9c425370c..71179ed9f743d 100644
--- a/llvm/lib/CodeGen/MachineFunction.cpp
+++ b/llvm/lib/CodeGen/MachineFunction.cpp
@@ -20,6 +20,7 @@
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/StringSwitch.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/ProfileSummaryInfo.h"
@@ -161,6 +162,21 @@ static inline Align getFnStackAlignment(const TargetSubtargetInfo &STI,
return STI.getFrameLowering()->getStackAlign();
}
+static FramePointerKind getFramePointerPolicy(const Function &F) {
+ Attribute FPAttr = F.getFnAttribute("frame-pointer");
+ if (!FPAttr.isValid())
+ return FramePointerKind::None;
+
+ StringRef FP = FPAttr.getValueAsString();
+ return StringSwitch<FramePointerKind>(FP)
+ .Case("all", FramePointerKind::All)
+ .Case("non-leaf", FramePointerKind::NonLeaf)
+ .Case("non-leaf-no-reserve", FramePointerKind::NonLeafNoReserve)
+ .Case("reserved", FramePointerKind::Reserved)
+ .Case("none", FramePointerKind::None)
+ .Default(FramePointerKind::None);
+}
+
MachineFunction::MachineFunction(Function &F, const TargetMachine &Target,
const TargetSubtargetInfo &STI, MCContext &Ctx,
unsigned FunctionNum)
@@ -202,6 +218,7 @@ void MachineFunction::init() {
FrameInfo = new (Allocator) MachineFrameInfo(
getFnStackAlignment(STI, F), /*StackRealignable=*/CanRealignSP,
/*ForcedRealign=*/ForceRealignSP && CanRealignSP);
+ FrameInfo->setFramePointerPolicy(getFramePointerPolicy(F));
setUnsafeStackSize(F, *FrameInfo);
diff --git a/llvm/lib/CodeGen/TargetOptionsImpl.cpp b/llvm/lib/CodeGen/TargetOptionsImpl.cpp
index 16d86b42db4a3..2dbde46ac62e3 100644
--- a/llvm/lib/CodeGen/TargetOptionsImpl.cpp
+++ b/llvm/lib/CodeGen/TargetOptionsImpl.cpp
@@ -10,7 +10,6 @@
//
//===----------------------------------------------------------------------===//
-#include "llvm/ADT/StringSwitch.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
@@ -22,31 +21,33 @@ using namespace llvm;
/// DisableFramePointerElim - This returns true if frame pointer elimination
/// optimization should be disabled for the given machine function.
bool TargetOptions::DisableFramePointerElim(const MachineFunction &MF) const {
- const Function &F = MF.getFunction();
-
- Attribute FPAttr = F.getFnAttribute("frame-pointer");
- if (!FPAttr.isValid())
- return false;
- StringRef FP = FPAttr.getValueAsString();
- if (FP == "all")
+ FramePointerKind FP = MF.getFrameInfo().getFramePointerPolicy();
+ switch (FP) {
+ case FramePointerKind::All:
return true;
- if (FP == "non-leaf" || FP == "non-leaf-no-reserve")
+ case FramePointerKind::NonLeaf:
+ case FramePointerKind::NonLeafNoReserve:
return MF.getFrameInfo().hasCalls();
- if (FP == "none" || FP == "reserved")
+ case FramePointerKind::None:
+ case FramePointerKind::Reserved:
return false;
+ }
llvm_unreachable("unknown frame pointer flag");
}
bool TargetOptions::FramePointerIsReserved(const MachineFunction &MF) const {
- const Function &F = MF.getFunction();
- Attribute FPAttr = F.getFnAttribute("frame-pointer");
- if (!FPAttr.isValid())
+ FramePointerKind FP = MF.getFrameInfo().getFramePointerPolicy();
+ switch (FP) {
+ case FramePointerKind::All:
+ case FramePointerKind::NonLeaf:
+ case FramePointerKind::Reserved:
+ return true;
+ case FramePointerKind::NonLeafNoReserve:
+ return MF.getFrameInfo().hasCalls();
+ case FramePointerKind::None:
return false;
-
- return StringSwitch<bool>(FPAttr.getValueAsString())
- .Cases({"all", "non-leaf", "reserved"}, true)
- .Case(("non-leaf-no-reserve"), MF.getFrameInfo().hasCalls())
- .Case("none", false);
+ }
+ llvm_unreachable("unknown frame pointer flag");
}
/// HonorSignDependentRoundingFPMath - Return true if the codegen must assume
>From 975f2aea805b3affca3fd8a3c0349d96c65d71e9 Mon Sep 17 00:00:00 2001
From: Cullen Rhodes <cullen.rhodes at arm.com>
Date: Tue, 14 Apr 2026 15:05:08 +0000
Subject: [PATCH 2/3] address comments
---
llvm/include/llvm/CodeGen/MIRYamlMapping.h | 14 ++++++++++++++
llvm/lib/CodeGen/MIRParser/MIRParser.cpp | 2 ++
llvm/lib/CodeGen/MIRPrinter.cpp | 1 +
llvm/test/CodeGen/MIR/Generic/frame-info.mir | 4 +++-
.../tools/llvm-reduce/mir/preserve-frame-info.mir | 2 ++
5 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/llvm/include/llvm/CodeGen/MIRYamlMapping.h b/llvm/include/llvm/CodeGen/MIRYamlMapping.h
index f3e1ff91f453c..295ee296f78ab 100644
--- a/llvm/include/llvm/CodeGen/MIRYamlMapping.h
+++ b/llvm/include/llvm/CodeGen/MIRYamlMapping.h
@@ -17,6 +17,7 @@
#include "llvm/ADT/StringRef.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
+#include "llvm/Support/CodeGen.h"
#include "llvm/Support/SMLoc.h"
#include "llvm/Support/YAMLTraits.h"
#include "llvm/Support/raw_ostream.h"
@@ -144,6 +145,16 @@ template <> struct ScalarEnumerationTraits<MachineJumpTableInfo::JTEntryKind> {
}
};
+template <> struct ScalarEnumerationTraits<FramePointerKind> {
+ static void enumeration(IO &IO, FramePointerKind &FP) {
+ IO.enumCase(FP, "none", FramePointerKind::None);
+ IO.enumCase(FP, "non-leaf", FramePointerKind::NonLeaf);
+ IO.enumCase(FP, "all", FramePointerKind::All);
+ IO.enumCase(FP, "reserved", FramePointerKind::Reserved);
+ IO.enumCase(FP, "non-leaf-no-reserve", FramePointerKind::NonLeafNoReserve);
+ }
+};
+
template <> struct ScalarTraits<MaybeAlign> {
static void output(const MaybeAlign &Alignment, void *,
llvm::raw_ostream &out) {
@@ -702,6 +713,7 @@ struct MachineFrameInfo {
unsigned MaxAlignment = 0;
bool AdjustsStack = false;
bool HasCalls = false;
+ FramePointerKind FramePointerPolicy = FramePointerKind::None;
StringValue StackProtector;
StringValue FunctionContext;
unsigned MaxCallFrameSize = ~0u; ///< ~0u means: not computed yet.
@@ -724,6 +736,7 @@ struct MachineFrameInfo {
OffsetAdjustment == Other.OffsetAdjustment &&
MaxAlignment == Other.MaxAlignment &&
AdjustsStack == Other.AdjustsStack && HasCalls == Other.HasCalls &&
+ FramePointerPolicy == Other.FramePointerPolicy &&
StackProtector == Other.StackProtector &&
FunctionContext == Other.FunctionContext &&
MaxCallFrameSize == Other.MaxCallFrameSize &&
@@ -751,6 +764,7 @@ template <> struct MappingTraits<MachineFrameInfo> {
YamlIO.mapOptional("maxAlignment", MFI.MaxAlignment, (unsigned)0);
YamlIO.mapOptional("adjustsStack", MFI.AdjustsStack, false);
YamlIO.mapOptional("hasCalls", MFI.HasCalls, false);
+ YamlIO.mapOptional("framePointerPolicy", MFI.FramePointerPolicy);
YamlIO.mapOptional("stackProtector", MFI.StackProtector,
StringValue()); // Don't print it out when it's empty.
YamlIO.mapOptional("functionContext", MFI.FunctionContext,
diff --git a/llvm/lib/CodeGen/MIRParser/MIRParser.cpp b/llvm/lib/CodeGen/MIRParser/MIRParser.cpp
index db5bc67776c7d..00967e1de43cc 100644
--- a/llvm/lib/CodeGen/MIRParser/MIRParser.cpp
+++ b/llvm/lib/CodeGen/MIRParser/MIRParser.cpp
@@ -900,6 +900,8 @@ bool MIRParserImpl::initializeFrameInfo(PerFunctionMIParsingState &PFS,
MFI.ensureMaxAlignment(Align(YamlMFI.MaxAlignment));
MFI.setAdjustsStack(YamlMFI.AdjustsStack);
MFI.setHasCalls(YamlMFI.HasCalls);
+ if (YamlMFI.FramePointerPolicy != FramePointerKind::None)
+ MFI.setFramePointerPolicy(YamlMFI.FramePointerPolicy);
if (YamlMFI.MaxCallFrameSize != ~0u)
MFI.setMaxCallFrameSize(YamlMFI.MaxCallFrameSize);
MFI.setCVBytesOfCalleeSavedRegisters(YamlMFI.CVBytesOfCalleeSavedRegisters);
diff --git a/llvm/lib/CodeGen/MIRPrinter.cpp b/llvm/lib/CodeGen/MIRPrinter.cpp
index 250b40863c9f3..60202efcd7af5 100644
--- a/llvm/lib/CodeGen/MIRPrinter.cpp
+++ b/llvm/lib/CodeGen/MIRPrinter.cpp
@@ -364,6 +364,7 @@ static void convertMFI(ModuleSlotTracker &MST, yaml::MachineFrameInfo &YamlMFI,
YamlMFI.MaxAlignment = MFI.getMaxAlign().value();
YamlMFI.AdjustsStack = MFI.adjustsStack();
YamlMFI.HasCalls = MFI.hasCalls();
+ YamlMFI.FramePointerPolicy = MFI.getFramePointerPolicy();
YamlMFI.MaxCallFrameSize = MFI.isMaxCallFrameSizeComputed()
? MFI.getMaxCallFrameSize() : ~0u;
YamlMFI.CVBytesOfCalleeSavedRegisters =
diff --git a/llvm/test/CodeGen/MIR/Generic/frame-info.mir b/llvm/test/CodeGen/MIR/Generic/frame-info.mir
index 32396b7486fe5..8992e9f51f8ef 100644
--- a/llvm/test/CodeGen/MIR/Generic/frame-info.mir
+++ b/llvm/test/CodeGen/MIR/Generic/frame-info.mir
@@ -36,6 +36,7 @@ tracksRegLiveness: true
# CHECK-NEXT: maxAlignment:
# CHECK-NEXT: adjustsStack: false
# CHECK-NEXT: hasCalls: false
+# CHECK-NEXT: framePointerPolicy: none
# CHECK-NEXT: stackProtector: ''
# CHECK-NEXT: functionContext: ''
# CHECK-NEXT: maxCallFrameSize:
@@ -70,6 +71,7 @@ stack:
# CHECK-NEXT: maxAlignment:
# CHECK-NEXT: adjustsStack: true
# CHECK-NEXT: hasCalls: true
+# CHECK-NEXT: framePointerPolicy: non-leaf
# CHECK-NEXT: stackProtector: ''
# CHECK-NEXT: functionContext: '%stack.0'
# CHECK-NEXT: maxCallFrameSize: 4
@@ -89,6 +91,7 @@ frameInfo:
maxAlignment: 4
adjustsStack: true
hasCalls: true
+ framePointerPolicy: non-leaf
functionContext: '%stack.0'
maxCallFrameSize: 4
cvBytesOfCalleeSavedRegisters: 8
@@ -100,4 +103,3 @@ frameInfo:
body: |
bb.0.entry:
...
-
diff --git a/llvm/test/tools/llvm-reduce/mir/preserve-frame-info.mir b/llvm/test/tools/llvm-reduce/mir/preserve-frame-info.mir
index 9af4ac3863405..eb01fbef2cb14 100644
--- a/llvm/test/tools/llvm-reduce/mir/preserve-frame-info.mir
+++ b/llvm/test/tools/llvm-reduce/mir/preserve-frame-info.mir
@@ -13,6 +13,7 @@
# RESULT-NEXT: maxAlignment: 64
# RESULT-NEXT: adjustsStack: true
# RESULT-NEXT: hasCalls: true
+# RESULT-NEXT: framePointerPolicy: none
# RESULT-NEXT: stackProtector: '%stack.9.guard'
# RESULT-NEXT: maxCallFrameSize: 420
# RESULT-NEXT: cvBytesOfCalleeSavedRegisters: 48
@@ -110,6 +111,7 @@ frameInfo:
maxAlignment: 1
adjustsStack: true
hasCalls: true
+ framePointerPolicy: none
stackProtector: '%stack.9'
maxCallFrameSize: 420
cvBytesOfCalleeSavedRegisters: 48
>From b05b64c6a6e137ca722dc62861c3d0e6304f8d57 Mon Sep 17 00:00:00 2001
From: Cullen Rhodes <cullen.rhodes at arm.com>
Date: Fri, 17 Apr 2026 10:55:56 +0000
Subject: [PATCH 3/3] address comments
---
llvm/test/CodeGen/MIR/Generic/frame-info.mir | 98 +++++++++++++++++++-
1 file changed, 96 insertions(+), 2 deletions(-)
diff --git a/llvm/test/CodeGen/MIR/Generic/frame-info.mir b/llvm/test/CodeGen/MIR/Generic/frame-info.mir
index 8992e9f51f8ef..daf87feb2c712 100644
--- a/llvm/test/CodeGen/MIR/Generic/frame-info.mir
+++ b/llvm/test/CodeGen/MIR/Generic/frame-info.mir
@@ -20,6 +20,46 @@
ret i32 %c
}
+ define i32 @test_framePointerPolicy_none(i32 %a) {
+ entry:
+ %b = alloca i32
+ store i32 %a, ptr %b
+ %c = load i32, ptr %b
+ ret i32 %c
+ }
+
+ define i32 @test_framePointerPolicy_non_leaf(i32 %a) {
+ entry:
+ %b = alloca i32
+ store i32 %a, ptr %b
+ %c = load i32, ptr %b
+ ret i32 %c
+ }
+
+ define i32 @test_framePointerPolicy_all(i32 %a) {
+ entry:
+ %b = alloca i32
+ store i32 %a, ptr %b
+ %c = load i32, ptr %b
+ ret i32 %c
+ }
+
+ define i32 @test_framePointerPolicy_reserved(i32 %a) {
+ entry:
+ %b = alloca i32
+ store i32 %a, ptr %b
+ %c = load i32, ptr %b
+ ret i32 %c
+ }
+
+ define i32 @test_framePointerPolicy_non_leaf_no_reserve(i32 %a) {
+ entry:
+ %b = alloca i32
+ store i32 %a, ptr %b
+ %c = load i32, ptr %b
+ ret i32 %c
+ }
+
...
---
name: test
@@ -71,7 +111,7 @@ stack:
# CHECK-NEXT: maxAlignment:
# CHECK-NEXT: adjustsStack: true
# CHECK-NEXT: hasCalls: true
-# CHECK-NEXT: framePointerPolicy: non-leaf
+# CHECK-NEXT: framePointerPolicy: none
# CHECK-NEXT: stackProtector: ''
# CHECK-NEXT: functionContext: '%stack.0'
# CHECK-NEXT: maxCallFrameSize: 4
@@ -91,7 +131,6 @@ frameInfo:
maxAlignment: 4
adjustsStack: true
hasCalls: true
- framePointerPolicy: non-leaf
functionContext: '%stack.0'
maxCallFrameSize: 4
cvBytesOfCalleeSavedRegisters: 8
@@ -103,3 +142,58 @@ frameInfo:
body: |
bb.0.entry:
...
+---
+name: test_framePointerPolicy_none
+
+# CHECK: test_framePointerPolicy_none
+# CHECK: frameInfo:
+# CHECK: framePointerPolicy: none
+frameInfo:
+ framePointerPolicy: none
+body: |
+ bb.0.entry:
+...
+---
+name: test_framePointerPolicy_non_leaf
+
+# CHECK: test_framePointerPolicy_non_leaf
+# CHECK: frameInfo:
+# CHECK: framePointerPolicy: non-leaf
+frameInfo:
+ framePointerPolicy: non-leaf
+body: |
+ bb.0.entry:
+...
+---
+name: test_framePointerPolicy_all
+
+# CHECK: test_framePointerPolicy_all
+# CHECK: frameInfo:
+# CHECK: framePointerPolicy: all
+frameInfo:
+ framePointerPolicy: all
+body: |
+ bb.0.entry:
+...
+---
+name: test_framePointerPolicy_reserved
+
+# CHECK: test_framePointerPolicy_reserved
+# CHECK: frameInfo:
+# CHECK: framePointerPolicy: reserved
+frameInfo:
+ framePointerPolicy: reserved
+body: |
+ bb.0.entry:
+...
+---
+name: test_framePointerPolicy_non_leaf_no_reserve
+
+# CHECK: test_framePointerPolicy_non_leaf_no_reserve
+# CHECK: frameInfo:
+# CHECK: framePointerPolicy: non-leaf-no-reserve
+frameInfo:
+ framePointerPolicy: non-leaf-no-reserve
+body: |
+ bb.0.entry:
+...
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