[llvm] [SelectionDAG] Remove redundant vector checks (NFC) (PR #99524)

[via llvm-commits]

https://github.com/AtariDreams updated https://github.com/llvm/llvm-project/pull/99524

>From 14cd7d6ea32e6590b7dab0fc623ad51f71b21b3f Mon Sep 17 00:00:00 2001
From: Rose <gfunni234 at gmail.com>
Date: Thu, 18 Jul 2024 12:23:13 -0400
Subject: [PATCH] [SelectionDAG] Remove redundant vector checks (NFC)

It turns out that the function already exits early if N1 is not a constant or is a vector, so simplify.
---
 .../lib/CodeGen/GlobalISel/CombinerHelper.cpp |  4 ++--
 .../CodeGen/SelectionDAG/TargetLowering.cpp   | 20 +++++++------------
 2 files changed, 9 insertions(+), 15 deletions(-)

diff --git a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
index dfc3d73e322b8..41ddce2272210 100644
--- a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -5179,8 +5179,6 @@ MachineInstr *CombinerHelper::buildUDivUsingMul(MachineInstr &MI) {
   LLT ShiftAmtTy = getTargetLowering().getPreferredShiftAmountTy(Ty);
   LLT ScalarShiftAmtTy = ShiftAmtTy.getScalarType();
 
-  unsigned KnownLeadingZeros =
-      KB ? KB->getKnownBits(LHS).countMinLeadingZeros() : 0;
   auto &MIB = Builder;
 
   bool UseSRL = false;
@@ -5226,6 +5224,8 @@ MachineInstr *CombinerHelper::buildUDivUsingMul(MachineInstr &MI) {
     // TODO: Use undef values for divisor of 1.
     if (!Divisor.isOne()) {
 
+      unsigned KnownLeadingZeros =
+          KB ? KB->getKnownBits(LHS).countMinLeadingZeros() : 0;
       // UnsignedDivisionByConstantInfo doesn't work correctly if leading zeros
       // in the dividend exceeds the leading zeros for the divisor.
       UnsignedDivisionByConstantInfo magics =
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index c3a20b5044c5f..7f707d578f9c8 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -6481,18 +6481,6 @@ SDValue TargetLowering::BuildUDIV(SDNode *N, SelectionDAG &DAG,
   SDValue N0 = N->getOperand(0);
   SDValue N1 = N->getOperand(1);
 
-  // Try to use leading zeros of the dividend to reduce the multiplier and
-  // avoid expensive fixups.
-  // TODO: Support vectors.
-  unsigned LeadingZeros = 0;
-  if (!VT.isVector() && isa<ConstantSDNode>(N1)) {
-    assert(!isOneConstant(N1) && "Unexpected divisor");
-    LeadingZeros = DAG.computeKnownBits(N0).countMinLeadingZeros();
-    // UnsignedDivisionByConstantInfo doesn't work correctly if leading zeros in
-    // the dividend exceeds the leading zeros for the divisor.
-    LeadingZeros = std::min(LeadingZeros, N1->getAsAPIntVal().countl_zero());
-  }
-
   bool UseNPQ = false, UsePreShift = false, UsePostShift = false;
   SmallVector<SDValue, 16> PreShifts, PostShifts, MagicFactors, NPQFactors;
 
@@ -6509,8 +6497,14 @@ SDValue TargetLowering::BuildUDIV(SDNode *N, SelectionDAG &DAG,
       PreShift = PostShift = DAG.getUNDEF(ShSVT);
       MagicFactor = NPQFactor = DAG.getUNDEF(SVT);
     } else {
+      // Try to use leading zeros of the dividend to reduce the multiplier and
+      // avoid expensive fixups.
+      unsigned KnownLeadingZeros =
+          DAG.computeKnownBits(N0).countMinLeadingZeros();
+
       UnsignedDivisionByConstantInfo magics =
-          UnsignedDivisionByConstantInfo::get(Divisor, LeadingZeros);
+          UnsignedDivisionByConstantInfo::get(
+              Divisor, std::min(KnownLeadingZeros, Divisor.countl_zero()));
 
       MagicFactor = DAG.getConstant(magics.Magic, dl, SVT);