[llvm] [RISCV] Do not commute with shift if we might break a qc.shladd pattern (PR #155367)

[Sudharsan Veeravalli via llvm-commits]

https://github.com/svs-quic created https://github.com/llvm/llvm-project/pull/155367

Similar to what we do if might break a `sh{1,2,3}add` pattern.

>From 09fd5f399196f9188c3224ae65bed61f0a71bfa9 Mon Sep 17 00:00:00 2001
From: Sudharsan Veeravalli <quic_svs at quicinc.com>
Date: Tue, 26 Aug 2025 13:14:24 +0530
Subject: [PATCH] [RISCV] Do not commute with shift if we might break a
 qc.shladd pattern

---
 llvm/lib/Target/RISCV/RISCVISelLowering.cpp | 11 ++-
 llvm/test/CodeGen/RISCV/xqciac.ll           | 76 +++++++++++++++++++++
 2 files changed, 84 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index b84bd1ce0ac50..f636d3006584b 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -21120,9 +21120,14 @@ bool RISCVTargetLowering::isDesirableToCommuteWithShift(
     auto *C1 = dyn_cast<ConstantSDNode>(N0->getOperand(1));
     auto *C2 = dyn_cast<ConstantSDNode>(N->getOperand(1));
 
-    // Bail if we might break a sh{1,2,3}add pattern.
-    if ((Subtarget.hasStdExtZba() || Subtarget.hasVendorXAndesPerf()) && C2 &&
-        C2->getZExtValue() >= 1 && C2->getZExtValue() <= 3 && N->hasOneUse() &&
+    bool IsShXAdd =
+        (Subtarget.hasStdExtZba() || Subtarget.hasVendorXAndesPerf()) && C2 &&
+        C2->getZExtValue() >= 1 && C2->getZExtValue() <= 3;
+    bool IsQCShlAdd = Subtarget.hasVendorXqciac() && C2 &&
+                      C2->getZExtValue() >= 4 && C2->getZExtValue() <= 31;
+
+    // Bail if we might break a sh{1,2,3}add/qc.shladd pattern.
+    if ((IsShXAdd || IsQCShlAdd) && N->hasOneUse() &&
         N->user_begin()->getOpcode() == ISD::ADD &&
         !isUsedByLdSt(*N->user_begin(), nullptr) &&
         !isa<ConstantSDNode>(N->user_begin()->getOperand(1)))
diff --git a/llvm/test/CodeGen/RISCV/xqciac.ll b/llvm/test/CodeGen/RISCV/xqciac.ll
index 6fdc63fddbc30..1a6c7bed30338 100644
--- a/llvm/test/CodeGen/RISCV/xqciac.ll
+++ b/llvm/test/CodeGen/RISCV/xqciac.ll
@@ -490,3 +490,79 @@ define i32 @testmuliaddnegimm(i32 %a) {
   %add = add i32 %mul, 3
   ret i32 %add
 }
+
+define i32 @add_shl_OneUse_1(i32 %x) {
+; RV32IM-LABEL: add_shl_OneUse_1:
+; RV32IM:       # %bb.0:
+; RV32IM-NEXT:    ori a1, a0, 1
+; RV32IM-NEXT:    slli a0, a0, 4
+; RV32IM-NEXT:    ori a0, a0, 16
+; RV32IM-NEXT:    add a0, a0, a1
+; RV32IM-NEXT:    ret
+;
+; RV32IMXQCIAC-LABEL: add_shl_OneUse_1:
+; RV32IMXQCIAC:       # %bb.0:
+; RV32IMXQCIAC-NEXT:    ori a0, a0, 1
+; RV32IMXQCIAC-NEXT:    qc.shladd a0, a0, a0, 4
+; RV32IMXQCIAC-NEXT:    ret
+;
+; RV32IZBAMXQCIAC-LABEL: add_shl_OneUse_1:
+; RV32IZBAMXQCIAC:       # %bb.0:
+; RV32IZBAMXQCIAC-NEXT:    ori a0, a0, 1
+; RV32IZBAMXQCIAC-NEXT:    qc.shladd a0, a0, a0, 4
+; RV32IZBAMXQCIAC-NEXT:    ret
+  %or = or i32 %x, 1
+  %mul = shl i32 %or, 4
+  %add = add i32 %mul, %or
+  ret i32 %add
+}
+
+define i32 @add_shl_OneUse_2(i32 %x) {
+; RV32IM-LABEL: add_shl_OneUse_2:
+; RV32IM:       # %bb.0:
+; RV32IM-NEXT:    addi a0, a0, 1
+; RV32IM-NEXT:    slli a1, a0, 22
+; RV32IM-NEXT:    add a0, a1, a0
+; RV32IM-NEXT:    ret
+;
+; RV32IMXQCIAC-LABEL: add_shl_OneUse_2:
+; RV32IMXQCIAC:       # %bb.0:
+; RV32IMXQCIAC-NEXT:    addi a0, a0, 1
+; RV32IMXQCIAC-NEXT:    qc.shladd a0, a0, a0, 22
+; RV32IMXQCIAC-NEXT:    ret
+;
+; RV32IZBAMXQCIAC-LABEL: add_shl_OneUse_2:
+; RV32IZBAMXQCIAC:       # %bb.0:
+; RV32IZBAMXQCIAC-NEXT:    addi a0, a0, 1
+; RV32IZBAMXQCIAC-NEXT:    qc.shladd a0, a0, a0, 22
+; RV32IZBAMXQCIAC-NEXT:    ret
+  %or = add i32 %x, 1
+  %mul = shl i32 %or, 22
+  %add = add i32 %mul, %or
+  ret i32 %add
+}
+
+define i32 @add_shl_moreOneUse_3(i32 %x) {
+; RV32IM-LABEL: add_shl_moreOneUse_3:
+; RV32IM:       # %bb.0:
+; RV32IM-NEXT:    addi a0, a0, 1
+; RV32IM-NEXT:    slli a1, a0, 31
+; RV32IM-NEXT:    add a0, a1, a0
+; RV32IM-NEXT:    ret
+;
+; RV32IMXQCIAC-LABEL: add_shl_moreOneUse_3:
+; RV32IMXQCIAC:       # %bb.0:
+; RV32IMXQCIAC-NEXT:    addi a0, a0, 1
+; RV32IMXQCIAC-NEXT:    qc.shladd a0, a0, a0, 31
+; RV32IMXQCIAC-NEXT:    ret
+;
+; RV32IZBAMXQCIAC-LABEL: add_shl_moreOneUse_3:
+; RV32IZBAMXQCIAC:       # %bb.0:
+; RV32IZBAMXQCIAC-NEXT:    addi a0, a0, 1
+; RV32IZBAMXQCIAC-NEXT:    qc.shladd a0, a0, a0, 31
+; RV32IZBAMXQCIAC-NEXT:    ret
+  %or = add i32 %x, 1
+  %mul = shl i32 %or, 31
+  %add = add i32 %mul, %or
+  ret i32 %add
+}