[llvm] [RISCV] Simplify the check for when to call EmitLoweredCascadedSelect. NFC (PR #145930)

[Craig Topper via llvm-commits]

https://github.com/topperc created https://github.com/llvm/llvm-project/pull/145930

Based on the comments and tests, we only want to call EmitLoweredCascadedSelect on selects of FP registers.

Everytime we add a new branch with immediate opcode, we've been excluding it here.

This patch switches to checking that the comparison operands are both registers so branch on immediate is automatically excluded.

>From 09d76788555bf07ac652c4e6a0236c707882305e Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Thu, 26 Jun 2025 10:08:49 -0700
Subject: [PATCH] [RISCV] Simplify the check for when to call
 EmitLoweredCascadedSelect. NFC

Based on the comments and tests, we only want to call EmitLoweredCascadedSelect
on selects of FP registers.

Everytime we add a new branch with immediate opcode, we've been
excluding it here.

This patch switches to checking that the comparison operands are
both registers so branch on immediate is automatically excluded.
---
 llvm/lib/Target/RISCV/RISCVISelLowering.cpp | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
index 01722ee023060..683ce1fed9253 100644
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -21444,12 +21444,8 @@ static MachineBasicBlock *emitSelectPseudo(MachineInstr &MI,
   // EmitLoweredCascadedSelect.
 
   auto Next = next_nodbg(MI.getIterator(), BB->instr_end());
-  if ((MI.getOpcode() != RISCV::Select_GPR_Using_CC_GPR &&
-       MI.getOpcode() != RISCV::Select_GPR_Using_CC_SImm5_CV &&
-       MI.getOpcode() != RISCV::Select_GPRNoX0_Using_CC_SImm5NonZero_QC &&
-       MI.getOpcode() != RISCV::Select_GPRNoX0_Using_CC_UImm5NonZero_QC &&
-       MI.getOpcode() != RISCV::Select_GPRNoX0_Using_CC_SImm16NonZero_QC &&
-       MI.getOpcode() != RISCV::Select_GPRNoX0_Using_CC_UImm16NonZero_QC) &&
+  if (MI.getOpcode() != RISCV::Select_GPR_Using_CC_GPR &&
+      MI.getOperand(1).isReg() && MI.getOperand(2).isReg() &&
       Next != BB->end() && Next->getOpcode() == MI.getOpcode() &&
       Next->getOperand(5).getReg() == MI.getOperand(0).getReg() &&
       Next->getOperand(5).isKill())