From be72ad726aab58ae31be9c88ec984a3b00aa9dd5 Mon Sep 17 00:00:00 2001
From: Jakub Florek <j_florek@apple.com>
Date: Tue, 9 Sep 2025 17:02:29 +0100
Subject: [PATCH] Fix licm not projecting load path before load splitting.

---
 .../LoopInvariantCodeMotion.swift             |  3 +-
 test/SILOptimizer/licm.sil                    | 41 +++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/SwiftCompilerSources/Sources/Optimizer/FunctionPasses/LoopInvariantCodeMotion.swift b/SwiftCompilerSources/Sources/Optimizer/FunctionPasses/LoopInvariantCodeMotion.swift
index c250890da4080..04306c9dcedb3 100644
--- a/SwiftCompilerSources/Sources/Optimizer/FunctionPasses/LoopInvariantCodeMotion.swift
+++ b/SwiftCompilerSources/Sources/Optimizer/FunctionPasses/LoopInvariantCodeMotion.swift
@@ -587,7 +587,8 @@ private extension AnalyzedInstructions {
         continue
       }
 
-      guard let splitLoads = loadInst.trySplit(alongPath: accessPath.projectionPath, context) else {
+      guard let projectionPath =  loadInst.operand.value.accessPath.getProjection(to: accessPath),
+            let splitLoads = loadInst.trySplit(alongPath: projectionPath, context) else {
         newLoads.push(loadInst)
         return false
       }
diff --git a/test/SILOptimizer/licm.sil b/test/SILOptimizer/licm.sil
index 73c581511fa46..e456cefed10b5 100644
--- a/test/SILOptimizer/licm.sil
+++ b/test/SILOptimizer/licm.sil
@@ -1514,6 +1514,47 @@ bb2:
   return %r1 : $()
 }
 
+struct Outer {
+    var interactions: Inner
+}
+
+public struct Inner {
+    public let x: Int
+    var storage: ContiguousArray<Double>
+}
+
+sil @$get_array_from_inner : $@convention(method) (Inner) -> (ContiguousArray<Double>)
+
+// Make sure we project load access path to matching store access path.
+// Otherwise the pass could crash.
+//
+// CHECK-LABEL: sil @project_load_path_before_splitting_crash :
+// CHECK:         load
+// CHECK:       bb1(%8 : $ContiguousArray<Double>):
+// CHECK:       bb3:
+// CHECK:         store
+// CHECK:       } // end sil function 'project_load_path_before_splitting_crash'
+sil @project_load_path_before_splitting_crash : $@convention(thin) (@inout Outer) -> () {
+bb0(%0 : $*Outer):
+  %1 = struct_element_addr %0, #Outer.interactions
+  %2 = struct_element_addr %1, #Inner.storage
+  br bb1
+
+bb1:
+  %4 = load %1
+  %5 = function_ref @$get_array_from_inner : $@convention(method) (Inner) -> ContiguousArray<Double>
+  %6 = apply %5(%4) : $@convention(method) (Inner) -> ContiguousArray<Double>
+  store %6 to %2
+  cond_br undef, bb2, bb3
+
+bb2:
+  br bb1
+
+bb3:
+  %10 = tuple ()
+  return %10
+}
+
 // CHECK-LABEL: sil @dont_hoist_builtin_once_memory_conflict :
 // CHECK:         function_ref
 // CHECK:         br bb1