[llvm] a467c08 - [RISCV] Cleanup comment around vector tail policy handling. NFC

[Craig Topper via llvm-commits]

Author: Craig Topper
Date: 2021-07-21T12:45:08-07:00
New Revision: a467c085707c7b0b3110c21fa35ee8ddde73426e

URL: https://github.com/llvm/llvm-project/commit/a467c085707c7b0b3110c21fa35ee8ddde73426e
DIFF: https://github.com/llvm/llvm-project/commit/a467c085707c7b0b3110c21fa35ee8ddde73426e.diff

LOG: [RISCV] Cleanup comment around vector tail policy handling. NFC

vmv.x.s and reductions don't ignore tail policy anymore.

Added: 
    

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

Removed: 
    


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diff  --git a/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp b/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
index 9b97074fd95f..c65e78350bf1 100644
--- a/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
+++ b/llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp
@@ -373,11 +373,8 @@ static VSETVLIInfo computeInfoForInstr(const MachineInstr &MI, uint64_t TSFlags,
 
   // Default to tail agnostic unless the destination is tied to a source.
   // Unless the source is undef. In that case the user would have some control
-  // over the tail values. The tail policy is also ignored on instructions
-  // that only update element 0 like vmv.s.x or reductions so use agnostic
-  // there to match the common case.
-  // FIXME: This is conservatively correct, but we might want to detect that
-  // the input is undefined.
+  // over the tail values. Some pseudo instructions force a tail agnostic policy
+  // despite having a tied def.
   bool ForceTailAgnostic = RISCVII::doesForceTailAgnostic(TSFlags);
   bool TailAgnostic = true;
   unsigned UseOpIdx;