[llvm] [MISched] Make `getUnderlyingObjectsForInstr()` preserve unidentified objects (PR #225085)
Nathan Corbyn via llvm-commits
llvm-commits at lists.llvm.org
Thu Sep 24 04:09:59 PDT 2026
https://github.com/cofibrant updated https://github.com/llvm/llvm-project/pull/225085
>From 0718e7c1b9bf93bac06c8fe63734a398b0f0954b Mon Sep 17 00:00:00 2001
From: Nathan Corbyn <n_corbyn at apple.com>
Date: Mon, 21 Sep 2026 14:33:56 +0100
Subject: [PATCH 1/4] [MISched] Make `getUnderlyingObjectsForInstr()` preserve
unidentified objects
---
llvm/lib/CodeGen/ScheduleDAGInstrs.cpp | 79 ++++++++++++--------------
1 file changed, 37 insertions(+), 42 deletions(-)
diff --git a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
index c929276b219f7..6bd6c733ddc8f 100644
--- a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -128,49 +128,44 @@ static bool getUnderlyingObjectsForInstr(const MachineInstr *MI,
const MachineFrameInfo &MFI,
UnderlyingObjectsVector &Objects,
const DataLayout &DL) {
- auto AllMMOsOkay = [&]() {
- for (const MachineMemOperand *MMO : MI->memoperands()) {
- // TODO: Figure out whether isAtomic is really necessary (see D57601).
- if (MMO->isVolatile() || MMO->isAtomic())
- return false;
-
- if (const PseudoSourceValue *PSV = MMO->getPseudoValue()) {
- // Function that contain tail calls don't have unique PseudoSourceValue
- // objects. Two PseudoSourceValues might refer to the same or
- // overlapping locations. The client code calling this function assumes
- // this is not the case. So return a conservative answer of no known
- // object.
- if (MFI.hasTailCall())
- return false;
-
- // For now, ignore PseudoSourceValues which may alias LLVM IR values
- // because the code that uses this function has no way to cope with
- // such aliases.
- if (PSV->isAliased(&MFI))
- return false;
+ bool AllObjectsIdentified = true;
- Objects.push_back(PSV);
- } else if (const Value *V = MMO->getValue()) {
- SmallVector<Value *, 4> Objs;
- if (!getUnderlyingObjectsForCodeGen(V, Objs))
- return false;
-
- for (Value *V : Objs) {
- assert(isIdentifiedObject(V));
- Objects.push_back(V);
- }
- } else
- return false;
+ for (const MachineMemOperand *MMO : MI->memoperands()) {
+ // TODO: Figure out whether isAtomic is really necessary (see D57601).
+ if (MMO->isVolatile() || MMO->isAtomic()) {
+ AllObjectsIdentified = false;
+ continue;
}
- return true;
- };
- if (!AllMMOsOkay()) {
- Objects.clear();
- return false;
+ if (const PseudoSourceValue *PSV = MMO->getPseudoValue()) {
+ // Function that contain tail calls don't have unique PseudoSourceValue
+ // objects. Two PseudoSourceValues might refer to the same or
+ // overlapping locations. The client code calling this function assumes
+ // this is not the case. So return a conservative answer of no known
+ // object.
+ if (MFI.hasTailCall())
+ AllObjectsIdentified = false;
+
+ // For now, ignore PseudoSourceValues which may alias LLVM IR values
+ // because the code that uses this function has no way to cope with
+ // such aliases.
+ if (PSV->isAliased(&MFI))
+ AllObjectsIdentified = false;
+
+ Objects.push_back(PSV);
+ } else if (const Value *V = MMO->getValue()) {
+ SmallVector<Value *, 4> Objs;
+ AllObjectsIdentified &= getUnderlyingObjectsForCodeGen(V, Objs);
+
+ for (Value *V : Objs) {
+ assert(!AllObjectsIdentified || isIdentifiedObject(V));
+ Objects.push_back(V);
+ }
+ } else
+ AllObjectsIdentified = false;
}
- return true;
+ return AllObjectsIdentified;
}
void ScheduleDAGInstrs::startBlock(MachineBasicBlock *bb) {
@@ -926,11 +921,11 @@ void ScheduleDAGInstrs::buildSchedGraph(AAResults *AA,
// empty, or filled with the Values of memory locations which this
// SU depends on.
UnderlyingObjectsVector Objs;
- bool ObjsFound = getUnderlyingObjectsForInstr(&MI, MFI, Objs,
- MF.getDataLayout());
+ bool ObjsIdentified =
+ getUnderlyingObjectsForInstr(&MI, MFI, Objs, MF.getDataLayout());
if (MI.mayStore()) {
- if (!ObjsFound) {
+ if (!ObjsIdentified) {
// An unknown store depends on all stores and loads.
addChainDependencies(SU, Stores);
addChainDependencies(SU, Loads);
@@ -956,7 +951,7 @@ void ScheduleDAGInstrs::buildSchedGraph(AAResults *AA,
addChainDependencies(SU, Stores, UnknownValue);
}
} else { // SU is a load.
- if (!ObjsFound) {
+ if (!ObjsIdentified) {
// An unknown load depends on all stores.
addChainDependencies(SU, Stores);
>From 52186e3b521767581b93e5604e537c4dea61e0e4 Mon Sep 17 00:00:00 2001
From: Nathan Corbyn <n_corbyn at apple.com>
Date: Tue, 22 Sep 2026 10:24:39 +0100
Subject: [PATCH 2/4] Fixups
---
llvm/lib/CodeGen/ScheduleDAGInstrs.cpp | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
index 6bd6c733ddc8f..f5672bf26e2df 100644
--- a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -120,10 +120,10 @@ ScheduleDAGInstrs::ScheduleDAGInstrs(MachineFunction &mf,
SchedModel.init(&ST, EnableSchedModel, EnableSchedItins);
}
-/// If this machine instr has memory reference information and it can be
-/// tracked to a normal reference to a known object, return the Value
-/// for that object. This function returns false the memory location is
-/// unknown or may alias anything.
+/// If this machine instruction has memory reference information, collect the
+/// list of underlying objects in \p Objects. If any of these objects are
+/// unknown or may alias anything, return false. Atomic and volatile memory
+/// operands are skipped.
static bool getUnderlyingObjectsForInstr(const MachineInstr *MI,
const MachineFrameInfo &MFI,
UnderlyingObjectsVector &Objects,
@@ -149,7 +149,7 @@ static bool getUnderlyingObjectsForInstr(const MachineInstr *MI,
// For now, ignore PseudoSourceValues which may alias LLVM IR values
// because the code that uses this function has no way to cope with
// such aliases.
- if (PSV->isAliased(&MFI))
+ else if (PSV->isAliased(&MFI))
AllObjectsIdentified = false;
Objects.push_back(PSV);
>From 0bca8b4d80527af6adce35cad81f146c4cee772d Mon Sep 17 00:00:00 2001
From: Nathan Corbyn <n_corbyn at apple.com>
Date: Tue, 22 Sep 2026 14:11:08 +0100
Subject: [PATCH 3/4] Reformat
---
llvm/lib/CodeGen/ScheduleDAGInstrs.cpp | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)
diff --git a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
index f5672bf26e2df..fc943e437251d 100644
--- a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -138,19 +138,19 @@ static bool getUnderlyingObjectsForInstr(const MachineInstr *MI,
}
if (const PseudoSourceValue *PSV = MMO->getPseudoValue()) {
- // Function that contain tail calls don't have unique PseudoSourceValue
- // objects. Two PseudoSourceValues might refer to the same or
- // overlapping locations. The client code calling this function assumes
- // this is not the case. So return a conservative answer of no known
- // object.
- if (MFI.hasTailCall())
+ if (MFI.hasTailCall()) {
+ // Function that contain tail calls don't have unique PseudoSourceValue
+ // objects. Two PseudoSourceValues might refer to the same or
+ // overlapping locations. The client code calling this function assumes
+ // this is not the case. So return a conservative answer of no known
+ // object.
AllObjectsIdentified = false;
-
- // For now, ignore PseudoSourceValues which may alias LLVM IR values
- // because the code that uses this function has no way to cope with
- // such aliases.
- else if (PSV->isAliased(&MFI))
+ } else if (PSV->isAliased(&MFI)) {
+ // For now, ignore PseudoSourceValues which may alias LLVM IR values
+ // because the code that uses this function has no way to cope with such
+ // aliases.
AllObjectsIdentified = false;
+ }
Objects.push_back(PSV);
} else if (const Value *V = MMO->getValue()) {
>From 8920e38fd7bbf9e4bde237d6845c4ba8134a1dfc Mon Sep 17 00:00:00 2001
From: Nathan Corbyn <n_corbyn at apple.com>
Date: Wed, 23 Sep 2026 11:20:51 +0100
Subject: [PATCH 4/4] Fixups
---
llvm/lib/CodeGen/ScheduleDAGInstrs.cpp | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
index fc943e437251d..506887734c749 100644
--- a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -155,14 +155,16 @@ static bool getUnderlyingObjectsForInstr(const MachineInstr *MI,
Objects.push_back(PSV);
} else if (const Value *V = MMO->getValue()) {
SmallVector<Value *, 4> Objs;
- AllObjectsIdentified &= getUnderlyingObjectsForCodeGen(V, Objs);
+ bool ObjectsIdentified = getUnderlyingObjectsForCodeGen(V, Objs);
+ AllObjectsIdentified &= ObjectsIdentified;
for (Value *V : Objs) {
- assert(!AllObjectsIdentified || isIdentifiedObject(V));
+ assert(!ObjectsIdentified || isIdentifiedObject(V));
Objects.push_back(V);
}
- } else
+ } else {
AllObjectsIdentified = false;
+ }
}
return AllObjectsIdentified;
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