[llvm] 1ab5974 - [AArch64] Support commuted operands in performFlagSettingCombine (#162496)
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Mon Oct 13 05:09:32 PDT 2025
Author: Cullen Rhodes
Date: 2025-10-13T13:09:28+01:00
New Revision: 1ab59745eeafd288d7139eb95d8f35ded2f0b583
URL: https://github.com/llvm/llvm-project/commit/1ab59745eeafd288d7139eb95d8f35ded2f0b583
DIFF: https://github.com/llvm/llvm-project/commit/1ab59745eeafd288d7139eb95d8f35ded2f0b583.diff
LOG: [AArch64] Support commuted operands in performFlagSettingCombine (#162496)
Fixes #122624.
Assisted-by: gpt-5-codex
Added:
Modified:
llvm/include/llvm/CodeGen/SelectionDAG.h
llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
llvm/test/CodeGen/AArch64/adds_cmn.ll
llvm/test/CodeGen/AArch64/sat-add.ll
Removed:
################################################################################
diff --git a/llvm/include/llvm/CodeGen/SelectionDAG.h b/llvm/include/llvm/CodeGen/SelectionDAG.h
index 62c0806dada2e..df6ce0fe1b037 100644
--- a/llvm/include/llvm/CodeGen/SelectionDAG.h
+++ b/llvm/include/llvm/CodeGen/SelectionDAG.h
@@ -1850,9 +1850,11 @@ class SelectionDAG {
/// Get the specified node if it's already available, or else return NULL.
LLVM_ABI SDNode *getNodeIfExists(unsigned Opcode, SDVTList VTList,
ArrayRef<SDValue> Ops,
- const SDNodeFlags Flags);
+ const SDNodeFlags Flags,
+ bool AllowCommute = false);
LLVM_ABI SDNode *getNodeIfExists(unsigned Opcode, SDVTList VTList,
- ArrayRef<SDValue> Ops);
+ ArrayRef<SDValue> Ops,
+ bool AllowCommute = false);
/// Check if a node exists without modifying its flags.
LLVM_ABI bool doesNodeExist(unsigned Opcode, SDVTList VTList,
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 08af74c258899..2b8dd60870696 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -11844,25 +11844,38 @@ SDValue SelectionDAG::getTargetInsertSubreg(int SRIdx, const SDLoc &DL, EVT VT,
/// getNodeIfExists - Get the specified node if it's already available, or
/// else return NULL.
SDNode *SelectionDAG::getNodeIfExists(unsigned Opcode, SDVTList VTList,
- ArrayRef<SDValue> Ops) {
+ ArrayRef<SDValue> Ops,
+ bool AllowCommute) {
SDNodeFlags Flags;
if (Inserter)
Flags = Inserter->getFlags();
- return getNodeIfExists(Opcode, VTList, Ops, Flags);
+ return getNodeIfExists(Opcode, VTList, Ops, Flags, AllowCommute);
}
SDNode *SelectionDAG::getNodeIfExists(unsigned Opcode, SDVTList VTList,
ArrayRef<SDValue> Ops,
- const SDNodeFlags Flags) {
- if (VTList.VTs[VTList.NumVTs - 1] != MVT::Glue) {
+ const SDNodeFlags Flags,
+ bool AllowCommute) {
+ if (VTList.VTs[VTList.NumVTs - 1] == MVT::Glue)
+ return nullptr;
+
+ auto Lookup = [&](ArrayRef<SDValue> LookupOps) -> SDNode * {
FoldingSetNodeID ID;
- AddNodeIDNode(ID, Opcode, VTList, Ops);
+ AddNodeIDNode(ID, Opcode, VTList, LookupOps);
void *IP = nullptr;
- if (SDNode *E = FindNodeOrInsertPos(ID, SDLoc(), IP)) {
+ if (SDNode *E = FindNodeOrInsertPos(ID, IP)) {
E->intersectFlagsWith(Flags);
return E;
}
- }
+ return nullptr;
+ };
+
+ if (SDNode *Existing = Lookup(Ops))
+ return Existing;
+
+ if (AllowCommute && TLI->isCommutativeBinOp(Opcode))
+ return Lookup({Ops[1], Ops[0]});
+
return nullptr;
}
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 69651168f8539..9926a4d7baec6 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -26196,9 +26196,10 @@ static SDValue performFlagSettingCombine(SDNode *N,
return DCI.CombineTo(N, Res, SDValue(N, 1));
}
- // Combine identical generic nodes into this node, re-using the result.
+ // Combine equivalent generic nodes into this node, re-using the result.
if (SDNode *Generic = DCI.DAG.getNodeIfExists(
- GenericOpcode, DCI.DAG.getVTList(VT), {LHS, RHS}))
+ GenericOpcode, DCI.DAG.getVTList(VT), {LHS, RHS},
+ /*AllowCommute=*/true))
DCI.CombineTo(Generic, SDValue(N, 0));
return SDValue();
diff --git a/llvm/test/CodeGen/AArch64/adds_cmn.ll b/llvm/test/CodeGen/AArch64/adds_cmn.ll
index aa070b7886ba5..9b456a5419d61 100644
--- a/llvm/test/CodeGen/AArch64/adds_cmn.ll
+++ b/llvm/test/CodeGen/AArch64/adds_cmn.ll
@@ -22,10 +22,8 @@ entry:
define { i32, i32 } @adds_cmn_c(i32 noundef %x, i32 noundef %y) {
; CHECK-LABEL: adds_cmn_c:
; CHECK: // %bb.0: // %entry
-; CHECK-NEXT: cmn w0, w1
-; CHECK-NEXT: add w1, w1, w0
-; CHECK-NEXT: cset w8, lo
-; CHECK-NEXT: mov w0, w8
+; CHECK-NEXT: adds w1, w0, w1
+; CHECK-NEXT: cset w0, lo
; CHECK-NEXT: ret
entry:
%0 = tail call { i32, i1 } @llvm.uadd.with.overflow.i32(i32 %x, i32 %y)
diff --git a/llvm/test/CodeGen/AArch64/sat-add.ll b/llvm/test/CodeGen/AArch64/sat-add.ll
index ecd48d6b7c65b..149b4c4fd26c9 100644
--- a/llvm/test/CodeGen/AArch64/sat-add.ll
+++ b/llvm/test/CodeGen/AArch64/sat-add.ll
@@ -290,8 +290,7 @@ define i32 @unsigned_sat_variable_i32_using_cmp_sum(i32 %x, i32 %y) {
define i32 @unsigned_sat_variable_i32_using_cmp_notval(i32 %x, i32 %y) {
; CHECK-LABEL: unsigned_sat_variable_i32_using_cmp_notval:
; CHECK: // %bb.0:
-; CHECK-NEXT: add w8, w0, w1
-; CHECK-NEXT: cmn w1, w0
+; CHECK-NEXT: adds w8, w1, w0
; CHECK-NEXT: csinv w0, w8, wzr, lo
; CHECK-NEXT: ret
%noty = xor i32 %y, -1
@@ -331,8 +330,7 @@ define i64 @unsigned_sat_variable_i64_using_cmp_sum(i64 %x, i64 %y) {
define i64 @unsigned_sat_variable_i64_using_cmp_notval(i64 %x, i64 %y) {
; CHECK-LABEL: unsigned_sat_variable_i64_using_cmp_notval:
; CHECK: // %bb.0:
-; CHECK-NEXT: add x8, x0, x1
-; CHECK-NEXT: cmn x1, x0
+; CHECK-NEXT: adds x8, x1, x0
; CHECK-NEXT: csinv x0, x8, xzr, lo
; CHECK-NEXT: ret
%noty = xor i64 %y, -1
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