[llvm] [DAG] combineVSelectWithAllOnesOrZeros - convert "select(setgt lhs, -1), 1, -1" match to SDPatternMatch. NFC. (PR #146842)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon updated https://github.com/llvm/llvm-project/pull/146842

>From 5ddbc41e88cc04820a4a40a68d791c373a8b73f3 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev at redking.me.uk>
Date: Thu, 3 Jul 2025 11:05:38 +0100
Subject: [PATCH] [DAG] combineVSelectWithAllOnesOrZeros - convert
 "select(setgt lhs, -1), 1, -1" match to SDPatternMatch. NFC.

---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 13 ++++---------
 llvm/test/CodeGen/AArch64/cmp-select-sign.ll  |  7 ++++---
 2 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index e7f1fdf10719a..821aecc06de04 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -13104,16 +13104,11 @@ static SDValue combineVSelectWithAllOnesOrZeros(SDValue Cond, SDValue TVal,
   }
 
   // check select(setgt lhs, -1), 1, -1 --> or (sra lhs, bitwidth - 1), 1
-  APInt TValAPInt;
-  if (Cond.getOpcode() == ISD::SETCC &&
-      Cond.getOperand(2) == DAG.getCondCode(ISD::SETGT) &&
-      Cond.getOperand(0).getValueType() == VT && VT.isSimple() &&
-      ISD::isConstantSplatVector(TVal.getNode(), TValAPInt) &&
-      TValAPInt.isOne() &&
-      ISD::isConstantSplatVectorAllOnes(Cond.getOperand(1).getNode()) &&
-      ISD::isConstantSplatVectorAllOnes(FVal.getNode())) {
+  if (VT.isSimple() && sd_match(TVal, m_One(/*AllowUndefs=*/true)) &&
+      sd_match(FVal, m_AllOnes(/*AllowUndefs=*/true)) &&
+      sd_match(Cond, m_SetCC(m_SpecificVT(VT), m_AllOnes(/*AllowUndefs=*/true),
+                             m_SpecificCondCode(ISD::SETGT))))
     return SDValue();
-  }
 
   // To use the condition operand as a bitwise mask, it must have elements that
   // are the same size as the select elements. i.e, the condition operand must
diff --git a/llvm/test/CodeGen/AArch64/cmp-select-sign.ll b/llvm/test/CodeGen/AArch64/cmp-select-sign.ll
index c2bb032eed78e..1a9c1bbac8817 100644
--- a/llvm/test/CodeGen/AArch64/cmp-select-sign.ll
+++ b/llvm/test/CodeGen/AArch64/cmp-select-sign.ll
@@ -114,9 +114,10 @@ define i64 @not_sign_i64_4(i64 %a) {
 define <7 x i8> @sign_7xi8(<7 x i8> %a) {
 ; CHECK-LABEL: sign_7xi8:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    movi v1.8b, #1
-; CHECK-NEXT:    cmlt v0.8b, v0.8b, #0
-; CHECK-NEXT:    orr v0.8b, v0.8b, v1.8b
+; CHECK-NEXT:    movi v1.2d, #0xffffffffffffffff
+; CHECK-NEXT:    movi v2.8b, #1
+; CHECK-NEXT:    cmge v0.8b, v1.8b, v0.8b
+; CHECK-NEXT:    orr v0.8b, v0.8b, v2.8b
 ; CHECK-NEXT:    ret
   %c = icmp sgt <7 x i8> %a, <i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1>
   %res = select <7 x i1> %c, <7 x i8> <i8 1, i8 1, i8 1, i8 1, i8 1, i8 1, i8 1>, <7 x i8> <i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1, i8 -1>