[llvm-branch-commits] [llvm] release/22.x: [RISCV] Run combineOrToBitfieldInsert after DAG legalize (#177830) (PR #178231)

[Cullen Rhodes via llvm-branch-commits]

https://github.com/c-rhodes updated https://github.com/llvm/llvm-project/pull/178231

>From 848164c632183b06c665fbba9e61e42bb4ac9635 Mon Sep 17 00:00:00 2001
From: Sudharsan Veeravalli <svs at qti.qualcomm.com>
Date: Mon, 26 Jan 2026 15:43:00 +0530
Subject: [PATCH] [RISCV] Run combineOrToBitfieldInsert after DAG legalize
 (#177830)

Not combing `OR` into `QC.INSB(I)` before DAG legalization helps known
bits analysis to simplify the code if possible.

(cherry picked from commit 3ed48305ab19bf0090d2ca714a37dd7b0667b6c2)
---
 llvm/lib/Target/RISCV/RISCVISelLowering.cpp |  7 ++++---
 llvm/test/CodeGen/RISCV/xqcibm-insert.ll    | 22 +++++++++++++++++++++
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index 2e9e5bbc65983..846e181b7e5af 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -17006,8 +17006,6 @@ static SDValue performORCombine(SDNode *N, TargetLowering::DAGCombinerInfo &DCI,
                                 const RISCVSubtarget &Subtarget) {
   SelectionDAG &DAG = DCI.DAG;
 
-  if (SDValue V = combineOrToBitfieldInsert(N, DAG, Subtarget))
-    return V;
   if (SDValue V = combineOrAndToBitfieldInsert(N, DAG, Subtarget))
     return V;
   if (SDValue V = combineBinOpToReduce(N, DAG, Subtarget))
@@ -17015,9 +17013,12 @@ static SDValue performORCombine(SDNode *N, TargetLowering::DAGCombinerInfo &DCI,
   if (SDValue V = combineBinOpOfExtractToReduceTree(N, DAG, Subtarget))
     return V;
 
-  if (DCI.isAfterLegalizeDAG())
+  if (DCI.isAfterLegalizeDAG()) {
+    if (SDValue V = combineOrToBitfieldInsert(N, DAG, Subtarget))
+      return V;
     if (SDValue V = combineDeMorganOfBoolean(N, DAG))
       return V;
+  }
 
   // Look for Or of CZERO_EQZ/NEZ with same condition which is the select idiom.
   // We may be able to pull a common operation out of the true and false value.
diff --git a/llvm/test/CodeGen/RISCV/xqcibm-insert.ll b/llvm/test/CodeGen/RISCV/xqcibm-insert.ll
index 234bd233ec9af..043a184d34ccd 100644
--- a/llvm/test/CodeGen/RISCV/xqcibm-insert.ll
+++ b/llvm/test/CodeGen/RISCV/xqcibm-insert.ll
@@ -401,3 +401,25 @@ define i32 @bseti_i32_10(i32 %a) nounwind {
   %or = or i32 %a, 1024
   ret i32 %or
 }
+
+define i1 @no_insbi_known_bits(i32 %arg) {
+; RV32I-LABEL: no_insbi_known_bits:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    li a0, 1
+; RV32I-NEXT:    ret
+;
+; RV32IXQCIBM-LABEL: no_insbi_known_bits:
+; RV32IXQCIBM:       # %bb.0:
+; RV32IXQCIBM-NEXT:    li a0, 1
+; RV32IXQCIBM-NEXT:    ret
+;
+; RV32IXQCIBMZBS-LABEL: no_insbi_known_bits:
+; RV32IXQCIBMZBS:       # %bb.0:
+; RV32IXQCIBMZBS-NEXT:    li a0, 1
+; RV32IXQCIBMZBS-NEXT:    ret
+  %a = or i32 %arg, 2147483647
+  %b = call i32 @llvm.bswap.i32(i32 %a)
+  %and = and i32 %b, 127
+  %res = icmp eq i32 %and, 127
+  ret i1 %res
+}