From 89b0de3563cf34d99acfad53ed68c44f9de20087 Mon Sep 17 00:00:00 2001
From: Erik Eckstein <eeckstein@apple.com>
Date: Fri, 14 Jul 2023 19:37:34 +0200
Subject: [PATCH] StackPromotion: fix a crash due to a problem in liferange
 evaluation

The analysis to check if an alloc_ref outlives it's "inner" liferange had a bug which resulted in a crash in the StackPromotion pass

rdar://112275272
---
 .../FunctionPasses/StackPromotion.swift       |  5 ++--
 test/SILOptimizer/stack_promotion.sil         | 24 +++++++++++++++++++
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/SwiftCompilerSources/Sources/Optimizer/FunctionPasses/StackPromotion.swift b/SwiftCompilerSources/Sources/Optimizer/FunctionPasses/StackPromotion.swift
index 4c3c9bedb7201..10c606fe7954a 100644
--- a/SwiftCompilerSources/Sources/Optimizer/FunctionPasses/StackPromotion.swift
+++ b/SwiftCompilerSources/Sources/Optimizer/FunctionPasses/StackPromotion.swift
@@ -289,14 +289,13 @@ private extension BasicBlockRange {
   /// Returns true if there is a direct edge connecting this range with the `otherRange`.
   func hasControlFlowEdge(to otherRange: BasicBlockRange) -> Bool {
     func isOnlyInOtherRange(_ block: BasicBlock) -> Bool {
-      return !inclusiveRangeContains(block) &&
-             otherRange.inclusiveRangeContains(block) && block != otherRange.begin
+      return !inclusiveRangeContains(block) && otherRange.inclusiveRangeContains(block)
     }
 
     for lifeBlock in inclusiveRange {
       assert(otherRange.inclusiveRangeContains(lifeBlock), "range must be a subset of other range")
       for succ in lifeBlock.successors {
-        if isOnlyInOtherRange(succ) {
+        if isOnlyInOtherRange(succ) && succ != otherRange.begin {
           return true
         }
         // The entry of the begin-block is conceptually not part of the range. We can check if
diff --git a/test/SILOptimizer/stack_promotion.sil b/test/SILOptimizer/stack_promotion.sil
index 805f940a494f3..ea2d6f7c96f37 100644
--- a/test/SILOptimizer/stack_promotion.sil
+++ b/test/SILOptimizer/stack_promotion.sil
@@ -1209,3 +1209,27 @@ bb3:
   br bb3
 }
 
+// CHECK-LABEL: sil @inner_liferange_jumps_to_outer_in_header_block
+// CHECK:         alloc_ref $XX
+// CHECK-LABEL: } // end sil function 'inner_liferange_jumps_to_outer_in_header_block'
+sil @inner_liferange_jumps_to_outer_in_header_block : $@convention(thin) (@owned XX) -> () {
+bb0(%0 : $XX):
+  %1 = alloc_stack $XX
+  br bb1(%0 : $XX)
+
+bb1(%2 : $XX):
+  strong_release %2 : $XX
+  %4 = alloc_ref $XX
+  store %4 to %1 : $*XX
+  cond_br undef, bb2, bb3
+
+bb2:
+  br bb1(%4 : $XX)
+
+bb3:
+  strong_release %4 : $XX
+  dealloc_stack %1 : $*XX
+  %r = tuple ()
+  return %r : $()
+}
+