[llvm-branch-commits] [llvm] 8e6d920 - [DAG][PowerPC] Fix dropped `nsw` flag in `SimplifySetCC` by adding `doesNodeExist` helper

[Kai Luo via llvm-branch-commits]

Author: Kai Luo
Date: 2020-11-25T04:39:03Z
New Revision: 8e6d92026c624386b85675a4664e2666225fcfac

URL: https://github.com/llvm/llvm-project/commit/8e6d92026c624386b85675a4664e2666225fcfac
DIFF: https://github.com/llvm/llvm-project/commit/8e6d92026c624386b85675a4664e2666225fcfac.diff

LOG: [DAG][PowerPC] Fix dropped `nsw` flag in `SimplifySetCC` by adding `doesNodeExist` helper

`SimplifySetCC` invokes `getNodeIfExists` without passing `Flags` argument and `getNodeIfExists` uses a default `SDNodeFlags` to intersect the original flags, as a consequence, flags like `nsw` is dropped. Added a new helper function `doesNodeExist` to check if a node exists without modifying its flags.

Reviewed By: #powerpc, nemanjai

Differential Revision: https://reviews.llvm.org/D89938

Added: 
    

Modified: 
    llvm/include/llvm/CodeGen/SelectionDAG.h
    llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
    llvm/test/CodeGen/PowerPC/setcc-sub-flag.ll

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/CodeGen/SelectionDAG.h b/llvm/include/llvm/CodeGen/SelectionDAG.h
index 8966e7f51dd9..cbd2e8b043a0 100644
--- a/llvm/include/llvm/CodeGen/SelectionDAG.h
+++ b/llvm/include/llvm/CodeGen/SelectionDAG.h
@@ -1520,6 +1520,9 @@ class SelectionDAG {
   SDNode *getNodeIfExists(unsigned Opcode, SDVTList VTList,
                           ArrayRef<SDValue> Ops);
 
+  /// Check if a node exists without modifying its flags.
+  bool doesNodeExist(unsigned Opcode, SDVTList VTList, ArrayRef<SDValue> Ops);
+
   /// Creates a SDDbgValue node.
   SDDbgValue *getDbgValue(DIVariable *Var, DIExpression *Expr, SDNode *N,
                           unsigned R, bool IsIndirect, const DebugLoc &DL,

diff  --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 489651e987ac..eee80cc4bc70 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -8326,6 +8326,19 @@ SDNode *SelectionDAG::getNodeIfExists(unsigned Opcode, SDVTList VTList,
   return nullptr;
 }
 
+/// doesNodeExist - Check if a node exists without modifying its flags.
+bool SelectionDAG::doesNodeExist(unsigned Opcode, SDVTList VTList,
+                                 ArrayRef<SDValue> Ops) {
+  if (VTList.VTs[VTList.NumVTs - 1] != MVT::Glue) {
+    FoldingSetNodeID ID;
+    AddNodeIDNode(ID, Opcode, VTList, Ops);
+    void *IP = nullptr;
+    if (FindNodeOrInsertPos(ID, SDLoc(), IP))
+      return true;
+  }
+  return false;
+}
+
 /// getDbgValue - Creates a SDDbgValue node.
 ///
 /// SDNode

diff  --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 1d51773dc2d8..93df88b3f6d7 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -3476,8 +3476,8 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
   if (!isConstOrConstSplat(N0) && !isConstOrConstSplat(N1) &&
       (DCI.isBeforeLegalizeOps() ||
        isCondCodeLegal(SwappedCC, N0.getSimpleValueType())) &&
-      DAG.getNodeIfExists(ISD::SUB, DAG.getVTList(OpVT), { N1, N0 } ) &&
-      !DAG.getNodeIfExists(ISD::SUB, DAG.getVTList(OpVT), { N0, N1 } ))
+      DAG.doesNodeExist(ISD::SUB, DAG.getVTList(OpVT), {N1, N0}) &&
+      !DAG.doesNodeExist(ISD::SUB, DAG.getVTList(OpVT), {N0, N1}))
     return DAG.getSetCC(dl, VT, N1, N0, SwappedCC);
 
   if (auto *N1C = isConstOrConstSplat(N1)) {

diff  --git a/llvm/test/CodeGen/PowerPC/setcc-sub-flag.ll b/llvm/test/CodeGen/PowerPC/setcc-sub-flag.ll
index ee4697b874e2..3d89fea12216 100644
--- a/llvm/test/CodeGen/PowerPC/setcc-sub-flag.ll
+++ b/llvm/test/CodeGen/PowerPC/setcc-sub-flag.ll
@@ -10,7 +10,7 @@ define void @f(i64 %a, i64 %b) {
   ; CHECK:   liveins: $x3, $x4
   ; CHECK:   [[COPY:%[0-9]+]]:g8rc = COPY $x4
   ; CHECK:   [[COPY1:%[0-9]+]]:g8rc = COPY $x3
-  ; CHECK:   [[SUBF8_:%[0-9]+]]:g8rc = SUBF8 [[COPY1]], [[COPY]]
+  ; CHECK:   [[SUBF8_:%[0-9]+]]:g8rc = nsw SUBF8 [[COPY1]], [[COPY]]
   %c = sub nsw i64 %b, %a
   call void @foo(i64 %c)
   %d = icmp slt i64 %a, %b