[llvm] [RISCV][VLOPT] Remove dead passthru check in getOperandLog2EEW. NFC (PR #123911)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-risc-v

Author: Luke Lau (lukel97)

<details>
<summary>Changes</summary>

We already bail if the user is tied in checkUsers, which is true for all passthrus. Remove the check in getOperandLog2EEW so that it only worries about computing the OperandInfo, and leaves the passthru correctness to checkUsers.


---
Full diff: https://github.com/llvm/llvm-project/pull/123911.diff


1 Files Affected:

- (modified) llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp (-7) 


``````````diff
diff --git a/llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp b/llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp
index 54ca8ccd8d9e90..2213339472c6ba 100644
--- a/llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp
+++ b/llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp
@@ -208,13 +208,6 @@ getOperandLog2EEW(const MachineOperand &MO, const MachineRegisterInfo *MRI) {
   const bool HasPassthru = RISCVII::isFirstDefTiedToFirstUse(MI.getDesc());
   const bool IsTied = RISCVII::isTiedPseudo(MI.getDesc().TSFlags);
 
-  // We bail out early for instructions that have passthru with non NoRegister,
-  // which means they are using TU policy. We are not interested in these
-  // since they must preserve the entire register content.
-  if (HasPassthru && MO.getOperandNo() == MI.getNumExplicitDefs() &&
-      (MO.getReg() != RISCV::NoRegister))
-    return std::nullopt;
-
   bool IsMODef = MO.getOperandNo() == 0;
 
   // All mask operands have EEW=1

``````````

</details>


https://github.com/llvm/llvm-project/pull/123911