[llvm] [TargetLowering][SelectionDAG] Exploit nneg Flag in UINT_TO_FP (PR #108931)

[Michael Marjieh via llvm-commits]

https://github.com/mmarjieh updated https://github.com/llvm/llvm-project/pull/108931

>From 92af8b44ae1b39e4b25eaabba411e22cfc4d848e Mon Sep 17 00:00:00 2001
From: Michael Marjieh <michael.marjieh at mobileye.com>
Date: Tue, 17 Sep 2024 08:49:00 +0300
Subject: [PATCH] [TargetLowering][SelectionDAG] Exploit nneg Flag in
 UINT_TO_FP

1. Propogate the nneg flag in WidenVecRes
2. Use SINT_TO_FP in expandUINT_TO_FP when possible.
---
 .../SelectionDAG/LegalizeVectorTypes.cpp      | 10 +++++-----
 .../CodeGen/SelectionDAG/TargetLowering.cpp   | 20 +++++++++++++------
 llvm/test/CodeGen/VE/Scalar/cast.ll           | 10 ++++++++++
 3 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
index 482f88e5c86de7..249cda171fbbf0 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -5205,7 +5205,7 @@ SDValue DAGTypeLegalizer::WidenVecRes_Convert(SDNode *N) {
   if (N->getOpcode() == ISD::ZERO_EXTEND &&
       getTypeAction(InVT) == TargetLowering::TypePromoteInteger &&
       TLI.getTypeToTransformTo(Ctx, InVT).getScalarSizeInBits() !=
-      WidenVT.getScalarSizeInBits()) {
+          WidenVT.getScalarSizeInBits()) {
     InOp = ZExtPromotedInteger(InOp);
     InVT = InOp.getValueType();
     if (WidenVT.getScalarSizeInBits() < InVT.getScalarSizeInBits())
@@ -5222,7 +5222,7 @@ SDValue DAGTypeLegalizer::WidenVecRes_Convert(SDNode *N) {
     InVTEC = InVT.getVectorElementCount();
     if (InVTEC == WidenEC) {
       if (N->getNumOperands() == 1)
-        return DAG.getNode(Opcode, DL, WidenVT, InOp);
+        return DAG.getNode(Opcode, DL, WidenVT, InOp, Flags);
       if (N->getNumOperands() == 3) {
         assert(N->isVPOpcode() && "Expected VP opcode");
         SDValue Mask =
@@ -5258,7 +5258,7 @@ SDValue DAGTypeLegalizer::WidenVecRes_Convert(SDNode *N) {
       Ops[0] = InOp;
       SDValue InVec = DAG.getNode(ISD::CONCAT_VECTORS, DL, InWidenVT, Ops);
       if (N->getNumOperands() == 1)
-        return DAG.getNode(Opcode, DL, WidenVT, InVec);
+        return DAG.getNode(Opcode, DL, WidenVT, InVec, Flags);
       return DAG.getNode(Opcode, DL, WidenVT, InVec, N->getOperand(1), Flags);
     }
 
@@ -5267,7 +5267,7 @@ SDValue DAGTypeLegalizer::WidenVecRes_Convert(SDNode *N) {
                                   DAG.getVectorIdxConstant(0, DL));
       // Extract the input and convert the shorten input vector.
       if (N->getNumOperands() == 1)
-        return DAG.getNode(Opcode, DL, WidenVT, InVal);
+        return DAG.getNode(Opcode, DL, WidenVT, InVal, Flags);
       return DAG.getNode(Opcode, DL, WidenVT, InVal, N->getOperand(1), Flags);
     }
   }
@@ -5282,7 +5282,7 @@ SDValue DAGTypeLegalizer::WidenVecRes_Convert(SDNode *N) {
     SDValue Val = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, DL, InEltVT, InOp,
                               DAG.getVectorIdxConstant(i, DL));
     if (N->getNumOperands() == 1)
-      Ops[i] = DAG.getNode(Opcode, DL, EltVT, Val);
+      Ops[i] = DAG.getNode(Opcode, DL, EltVT, Val, Flags);
     else
       Ops[i] = DAG.getNode(Opcode, DL, EltVT, Val, N->getOperand(1), Flags);
   }
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 95937886280685..0522958d5221c1 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -8361,18 +8361,26 @@ bool TargetLowering::expandFP_TO_UINT(SDNode *Node, SDValue &Result,
 }
 
 bool TargetLowering::expandUINT_TO_FP(SDNode *Node, SDValue &Result,
-                                      SDValue &Chain,
-                                      SelectionDAG &DAG) const {
+                                      SDValue &Chain, SelectionDAG &DAG) const {
+  SDValue Src = Node->getOperand(0);
+  EVT SrcVT = Src.getValueType();
+  EVT DstVT = Node->getValueType(0);
+
+  // If the input is known to be non-negative and SINT_TO_FP is legal then use
+  // it.
+  if (Node->getFlags().hasNonNeg() &&
+      isOperationLegalOrCustom(ISD::SINT_TO_FP, DstVT)) {
+    Result =
+        DAG.getNode(ISD::SINT_TO_FP, SDLoc(Node), DstVT, Node->getOperand(0));
+    return true;
+  }
+
   // This transform is not correct for converting 0 when rounding mode is set
   // to round toward negative infinity which will produce -0.0. So disable under
   // strictfp.
   if (Node->isStrictFPOpcode())
     return false;
 
-  SDValue Src = Node->getOperand(0);
-  EVT SrcVT = Src.getValueType();
-  EVT DstVT = Node->getValueType(0);
-
   if (SrcVT.getScalarType() != MVT::i64 || DstVT.getScalarType() != MVT::f64)
     return false;
 
diff --git a/llvm/test/CodeGen/VE/Scalar/cast.ll b/llvm/test/CodeGen/VE/Scalar/cast.ll
index 44782b342f4d0f..9253b5591b351d 100644
--- a/llvm/test/CodeGen/VE/Scalar/cast.ll
+++ b/llvm/test/CodeGen/VE/Scalar/cast.ll
@@ -568,6 +568,16 @@ define float @ull2f(i64 %x) {
   ret float %r
 }
 
+define float @ull2f_nneg(i64 %x) {
+; CHECK-LABEL: ull2f_nneg:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    cvt.d.l %s0, %s0
+; CHECK-NEXT:    cvt.s.d %s0, %s0
+; CHECK-NEXT:    b.l.t (, %s10)
+  %r = uitofp nneg i64 %x to float
+  ret float %r
+}
+
 define double @ull2d(i64 %x) {
 ; CHECK-LABEL: ull2d:
 ; CHECK:       # %bb.0: