[llvm] f4f7c71 - [RISCV][VLOPT] Move mayReadPastVL check into getMinimumVLForUser. NFC (#127972)

[via llvm-commits]

Author: Luke Lau
Date: 2025-02-20T20:17:18+08:00
New Revision: f4f7c71c55da442dc18e872d3c5db760a9ad43ba

URL: https://github.com/llvm/llvm-project/commit/f4f7c71c55da442dc18e872d3c5db760a9ad43ba
DIFF: https://github.com/llvm/llvm-project/commit/f4f7c71c55da442dc18e872d3c5db760a9ad43ba.diff

LOG: [RISCV][VLOPT] Move mayReadPastVL check into getMinimumVLForUser. NFC (#127972)

checkUsers currently does two things, a) work out the minimum VL read by
every user and b) check that the operand info of the MI and users match.

getMinimumVLForUser handles most of a), with the exception of the check
for instructions that read past VL e.g. vrgather which is still in
checkUsers.

This moves it into getMinimumVLForUser to keep all that logic in one
place and simplifies an upcoming patch.

Added: 
    

Modified: 
    llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp b/llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp
index ba2fcdc6d0670..c36a1e9adccb0 100644
--- a/llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp
+++ b/llvm/lib/Target/RISCV/RISCVVLOptimizer.cpp
@@ -1272,6 +1272,11 @@ RISCVVLOptimizer::getMinimumVLForUser(const MachineOperand &UserOp) const {
     return std::nullopt;
   }
 
+  if (mayReadPastVL(UserMI)) {
+    LLVM_DEBUG(dbgs() << "    Abort because used by unsafe instruction\n");
+    return std::nullopt;
+  }
+
   unsigned VLOpNum = RISCVII::getVLOpNum(Desc);
   const MachineOperand &VLOp = UserMI.getOperand(VLOpNum);
   // Looking for an immediate or a register VL that isn't X0.
@@ -1335,11 +1340,6 @@ RISCVVLOptimizer::checkUsers(const MachineInstr &MI) const {
       continue;
     }
 
-    if (mayReadPastVL(UserMI)) {
-      LLVM_DEBUG(dbgs() << "    Abort because used by unsafe instruction\n");
-      return std::nullopt;
-    }
-
     auto VLOp = getMinimumVLForUser(UserOp);
     if (!VLOp)
       return std::nullopt;