[llvm] [llvm-mca][Darwin] Fix crash on .subsections_via_symbols in asm input (PR #182694)

[dan rouhana via llvm-commits]

https://github.com/dr7ana updated https://github.com/llvm/llvm-project/pull/182694

>From 4bddebeb93d5e5b02fa67e4cfdea4f93f3a0cd44 Mon Sep 17 00:00:00 2001
From: dr7ana <danielrouhana at gmail.com>
Date: Sat, 21 Feb 2026 11:01:38 -0800
Subject: [PATCH 1/2] add no-op emitSubsectionsViaSymbols in MCStreamerWrapper
 for Darwin asm parsing

---
 llvm/tools/llvm-mca/CodeRegionGenerator.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/llvm/tools/llvm-mca/CodeRegionGenerator.h b/llvm/tools/llvm-mca/CodeRegionGenerator.h
index c30f67a53eac0..7083ba363081a 100644
--- a/llvm/tools/llvm-mca/CodeRegionGenerator.h
+++ b/llvm/tools/llvm-mca/CodeRegionGenerator.h
@@ -106,6 +106,7 @@ class MCStreamerWrapper : public MCStreamer {
   void emitZerofill(MCSection *Section, MCSymbol *Symbol = nullptr,
                     uint64_t Size = 0, Align ByteAlignment = Align(1),
                     SMLoc Loc = SMLoc()) override {}
+  void emitSubsectionsViaSymbols() override {}
   void beginCOFFSymbolDef(const MCSymbol *Symbol) override {}
   void emitCOFFSymbolStorageClass(int StorageClass) override {}
   void emitCOFFSymbolType(int Type) override {}

>From 608f257984f1c5a5a2de78e25988288579c3e3d3 Mon Sep 17 00:00:00 2001
From: dr7ana <danielrouhana at gmail.com>
Date: Sat, 21 Feb 2026 12:35:51 -0800
Subject: [PATCH 2/2] add llvm-mca test case for minimal reproducible example

---
 .../Apple/darwin-subsections-via-symbols.s    | 62 +++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 llvm/test/tools/llvm-mca/AArch64/Apple/darwin-subsections-via-symbols.s

diff --git a/llvm/test/tools/llvm-mca/AArch64/Apple/darwin-subsections-via-symbols.s b/llvm/test/tools/llvm-mca/AArch64/Apple/darwin-subsections-via-symbols.s
new file mode 100644
index 0000000000000..6b9d07aa50f84
--- /dev/null
+++ b/llvm/test/tools/llvm-mca/AArch64/Apple/darwin-subsections-via-symbols.s
@@ -0,0 +1,62 @@
+# NOTE: Assertions have been autogenerated by utils/update_mca_test_checks.py
+# RUN: llvm-mca -mtriple=arm64-apple-macos -mcpu=apple-m4 -iterations=1 < %s | FileCheck %s
+
+.text
+.subsections_via_symbols
+.globl _foo
+_foo:
+  ret
+
+# CHECK:      Iterations:        1
+# CHECK-NEXT: Instructions:      1
+# CHECK-NEXT: Total Cycles:      3
+# CHECK-NEXT: Total uOps:        1
+
+# CHECK:      Dispatch Width:    6
+# CHECK-NEXT: uOps Per Cycle:    0.33
+# CHECK-NEXT: IPC:               0.33
+# CHECK-NEXT: Block RThroughput: 1.0
+
+# CHECK:      Instruction Info:
+# CHECK-NEXT: [1]: #uOps
+# CHECK-NEXT: [2]: Latency
+# CHECK-NEXT: [3]: RThroughput
+# CHECK-NEXT: [4]: MayLoad
+# CHECK-NEXT: [5]: MayStore
+# CHECK-NEXT: [6]: HasSideEffects (U)
+
+# CHECK:      [1]    [2]    [3]    [4]    [5]    [6]    Instructions:
+# CHECK-NEXT:  1      0     1.00                  U     ret
+
+# CHECK:      Resources:
+# CHECK-NEXT: [0.0] - CyUnitB
+# CHECK-NEXT: [0.1] - CyUnitB
+# CHECK-NEXT: [1]   - CyUnitBR
+# CHECK-NEXT: [2.0] - CyUnitFloatDiv
+# CHECK-NEXT: [2.1] - CyUnitFloatDiv
+# CHECK-NEXT: [3.0] - CyUnitI
+# CHECK-NEXT: [3.1] - CyUnitI
+# CHECK-NEXT: [3.2] - CyUnitI
+# CHECK-NEXT: [3.3] - CyUnitI
+# CHECK-NEXT: [4]   - CyUnitID
+# CHECK-NEXT: [5]   - CyUnitIM
+# CHECK-NEXT: [6.0] - CyUnitIS
+# CHECK-NEXT: [6.1] - CyUnitIS
+# CHECK-NEXT: [7]   - CyUnitIntDiv
+# CHECK-NEXT: [8.0] - CyUnitLS
+# CHECK-NEXT: [8.1] - CyUnitLS
+# CHECK-NEXT: [9.0] - CyUnitV
+# CHECK-NEXT: [9.1] - CyUnitV
+# CHECK-NEXT: [9.2] - CyUnitV
+# CHECK-NEXT: [10]  - CyUnitVC
+# CHECK-NEXT: [11]  - CyUnitVD
+# CHECK-NEXT: [12.0] - CyUnitVM
+# CHECK-NEXT: [12.1] - CyUnitVM
+
+# CHECK:      Resource pressure per iteration:
+# CHECK-NEXT: [0.0]  [0.1]  [1]    [2.0]  [2.1]  [3.0]  [3.1]  [3.2]  [3.3]  [4]    [5]    [6.0]  [6.1]  [7]    [8.0]  [8.1]  [9.0]  [9.1]  [9.2]  [10]   [11]   [12.0] [12.1]
+# CHECK-NEXT:  -     1.00   1.00    -      -      -      -      -     1.00    -      -      -      -      -      -      -      -      -      -      -      -      -      -
+
+# CHECK:      Resource pressure by instruction:
+# CHECK-NEXT: [0.0]  [0.1]  [1]    [2.0]  [2.1]  [3.0]  [3.1]  [3.2]  [3.3]  [4]    [5]    [6.0]  [6.1]  [7]    [8.0]  [8.1]  [9.0]  [9.1]  [9.2]  [10]   [11]   [12.0] [12.1] Instructions:
+# CHECK-NEXT:  -     1.00   1.00    -      -      -      -      -     1.00    -      -      -      -      -      -      -      -      -      -      -      -      -      -     ret