[llvm] dfe8b22 - [BPF] Increase BPFMaxStoresPerMemFunc from 128 to 192 (#205222)

[via llvm-commits]

Author: yonghong-song
Date: 2026-06-22T18:02:14-07:00
New Revision: dfe8b229d3ec40e49250cc587009d5752b58b087

URL: https://github.com/llvm/llvm-project/commit/dfe8b229d3ec40e49250cc587009d5752b58b087
DIFF: https://github.com/llvm/llvm-project/commit/dfe8b229d3ec40e49250cc587009d5752b58b087.diff

LOG: [BPF] Increase BPFMaxStoresPerMemFunc from 128 to 192 (#205222)

With commits [1] and [2], memory operations like memcpy/memmove lower to
a sequence of loads/stores whose width is the minimum of the source and
destination alignment, and the store count is bounded by
BPFMaxStoresPerMemFunc. For 1-byte alignment, the maximum copy length
that can be inlined is therefore 128 bytes.

This may regress cases that previously inlined. Consider a memcpy with
src alignment 8, dst alignment 1 and size 136. After [1]/[2], the store
width is the minimum alignment (1 byte), so the store count is 136,
which exceeds the 128 limit and the copy falls back. Before [1]/[2], the
store count was computed with a fixed 8-byte unit regardless of the
actual alignment (each unit expands to 8 one-byte stores when the
minimum alignment is 1), so the total count was only 17 (136/8 < 128)
and the copy was inlined.

Raise the limit from 128 to 192 to mitigate. Alternatively, users can
increase alignment to avoid the regression.

  [1] https://github.com/llvm/llvm-project/pull/201119
  [2] https://github.com/llvm/llvm-project/pull/204042

Added: 
    

Modified: 
    llvm/lib/Target/BPF/BPFSelectionDAGInfo.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/BPF/BPFSelectionDAGInfo.cpp b/llvm/lib/Target/BPF/BPFSelectionDAGInfo.cpp
index 8b7ac6a4730f7..3e39a7393f251 100644
--- a/llvm/lib/Target/BPF/BPFSelectionDAGInfo.cpp
+++ b/llvm/lib/Target/BPF/BPFSelectionDAGInfo.cpp
@@ -22,7 +22,7 @@ using namespace llvm;
 #define DEBUG_TYPE "bpf-selectiondag-info"
 
 static cl::opt<unsigned> BPFMaxStoresPerMemFunc(
-    "bpf-max-stores-per-memfunc", cl::Hidden, cl::init(128),
+    "bpf-max-stores-per-memfunc", cl::Hidden, cl::init(192),
     cl::desc("Set the maximum number of stores for inlined BPF memory "
              "intrinsics"));