[llvm] [LegalizeTypes] Allow v1i128 as a valid SETCC result type during vector operand scalarization (PR #216136)

[Maryam Moghadas via llvm-commits]

https://github.com/maryammo created https://github.com/llvm/llvm-project/pull/216136

PowerPC registers v1i128 as a legal type when P8Altivec is available. When lowering <4 x fp128> comparisons, the type legalizer hits a v1i1 only assert. Relax the assert to also accept v1i128.

>From b8e57f280edcf2b7bc1ddd504ca315c7df22d9d9 Mon Sep 17 00:00:00 2001
From: Maryam Moghadas <maryammo at ca.ibm.com>
Date: Thu, 13 Aug 2026 17:52:15 +0000
Subject: [PATCH] Allow v1i128 as a valid SETCC result type during vector
 operand scalarization

---
 .../SelectionDAG/LegalizeVectorTypes.cpp      | 13 +++++++----
 .../CodeGen/PowerPC/fp128-vector-setcc.ll     | 22 +++++++++++++++++++
 2 files changed, 31 insertions(+), 4 deletions(-)
 create mode 100644 llvm/test/CodeGen/PowerPC/fp128-vector-setcc.ll

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
index 19b221bb98d46..a3f4f5c573e23 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -1114,13 +1114,16 @@ SDValue DAGTypeLegalizer::ScalarizeVecOp_VSELECT(SDNode *N) {
 }
 
 /// If the operand is a vector that needs to be scalarized then the
-/// result must be v1i1, so just convert to a scalar SETCC and wrap
-/// with a scalar_to_vector since the res type is legal if we got here
+/// result must be v1i1 or v1i128, so just convert to a scalar SETCC
+/// and wrap with a scalar_to_vector since the res type is legal if we
+/// got here
 SDValue DAGTypeLegalizer::ScalarizeVecOp_VSETCC(SDNode *N) {
   assert(N->getValueType(0).isVector() &&
          N->getOperand(0).getValueType().isVector() &&
          "Operand types must be vectors");
-  assert(N->getValueType(0) == MVT::v1i1 && "Expected v1i1 type");
+  assert(
+      (N->getValueType(0) == MVT::v1i1 || N->getValueType(0) == MVT::v1i128) &&
+      "Expected v1i1 or v1i128 type");
 
   EVT VT = N->getValueType(0);
   SDValue LHS = GetScalarizedVector(N->getOperand(0));
@@ -1150,7 +1153,9 @@ SDValue DAGTypeLegalizer::ScalarizeVecOp_VSTRICT_FSETCC(SDNode *N,
   assert(N->getValueType(0).isVector() &&
          N->getOperand(1).getValueType().isVector() &&
          "Operand types must be vectors");
-  assert(N->getValueType(0) == MVT::v1i1 && "Expected v1i1 type");
+  assert(
+      (N->getValueType(0) == MVT::v1i1 || N->getValueType(0) == MVT::v1i128) &&
+      "Expected v1i1 or v1i128 type");
 
   EVT VT = N->getValueType(0);
   SDValue Ch = N->getOperand(0);
diff --git a/llvm/test/CodeGen/PowerPC/fp128-vector-setcc.ll b/llvm/test/CodeGen/PowerPC/fp128-vector-setcc.ll
new file mode 100644
index 0000000000000..1d0c83edd8b78
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/fp128-vector-setcc.ll
@@ -0,0 +1,22 @@
+; RUN: llc -mtriple=powerpc64le-unknown-linux-gnu -mcpu=pwr8 %s -o - | FileCheck %s
+
+define <4 x i1> @fp(<4 x fp128> %0)  {
+; CHECK-LABEL: fp:
+; CHECK-COUNT-4: bl __eqkf2
+; CHECK: blr
+Entry:
+  %1 = fcmp oeq <4 x fp128> %0, zeroinitializer
+  ret <4 x i1> %1
+}
+
+define <4 x i1> @foo(<4 x fp128> %0) strictfp {
+; CHECK-LABEL: foo:
+; CHECK-COUNT-4: bl __eqkf2
+; CHECK: blr
+Entry:
+  %1 = call <4 x i1> @llvm.experimental.constrained.fcmp.v4fp128(<4 x fp128> %0, <4 x fp128> zeroinitializer, metadata !"oeq", metadata !"fpexcept.strict")
+  ret <4 x i1> %1
+}
+
+declare <4 x i1> @llvm.experimental.constrained.fcmp.v4fp128(<4 x fp128>, <4 x fp128>, metadata, metadata)
+