[llvm] [CodeGen] Skip pseudo instructions in AggressiveAntiDepBreaker (PR #222271)

[Pengcheng Wang via llvm-commits]

https://github.com/wangpc-pp created https://github.com/llvm/llvm-project/pull/222271

`ScheduleDAGInstrs` does not create SUnits for debug or pseudo instructions. The aggressive anti-dependency breaker only skipped debug instructions, so encountering a pseudo such as `PSEUDO_PROBE` dereferenced a null SUnit.

Skip both debug and pseudo instructions and add a Hexagon regression covering the existing aggressive anti-dependency path with legacy and new machine pass managers.

Split from #221984 in response to review.

>From 95a3243cd61544183351466b8e03edc8437f8119 Mon Sep 17 00:00:00 2001
From: Pengcheng Wang <wangpengcheng.pp at bytedance.com>
Date: Wed, 9 Sep 2026 16:46:47 +0800
Subject: [PATCH] [CodeGen] Skip pseudo instructions in
 AggressiveAntiDepBreaker

Pseudo instructions do not have SUnits in the post-RA scheduling DAG.
Skipping only debug instructions can therefore dereference a null SUnit.

Ignore pseudo instructions and add a PSEUDO_PROBE regression.

Assisted-by: TRAE CLI (GPT-5.6)
Co-authored-by: TRAE CLI <traecli at bytedance.com>
---
 llvm/lib/CodeGen/AggressiveAntiDepBreaker.cpp  | 2 +-
 llvm/test/CodeGen/Hexagon/anti-dep-partial.mir | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/CodeGen/AggressiveAntiDepBreaker.cpp b/llvm/lib/CodeGen/AggressiveAntiDepBreaker.cpp
index 6be353bb8da63..a425864921416 100644
--- a/llvm/lib/CodeGen/AggressiveAntiDepBreaker.cpp
+++ b/llvm/lib/CodeGen/AggressiveAntiDepBreaker.cpp
@@ -790,7 +790,7 @@ unsigned AggressiveAntiDepBreaker::BreakAntiDependencies(
        I != E; --Count) {
     MachineInstr &MI = *--I;
 
-    if (MI.isDebugInstr())
+    if (MI.isDebugOrPseudoInstr())
       continue;
 
     LLVM_DEBUG(dbgs() << "Anti: ");
diff --git a/llvm/test/CodeGen/Hexagon/anti-dep-partial.mir b/llvm/test/CodeGen/Hexagon/anti-dep-partial.mir
index b7a3f8051f698..1089d48793c6f 100644
--- a/llvm/test/CodeGen/Hexagon/anti-dep-partial.mir
+++ b/llvm/test/CodeGen/Hexagon/anti-dep-partial.mir
@@ -1,4 +1,5 @@
 # RUN: llc -mtriple=hexagon -post-RA-scheduler -run-pass post-RA-sched %s -o - | FileCheck %s
+# RUN: llc -mtriple=hexagon -post-RA-scheduler -passes=post-RA-sched %s -o - | FileCheck %s
 
 --- |
   declare void @check(i64, i32, i32, i64)
@@ -15,6 +16,7 @@ body: |
     successors:
     liveins: $r0, $r1, $d1, $d2, $r16, $r17, $r19, $r22, $r23
         $r2 = A2_add $r23, killed $r17
+        PSEUDO_PROBE 1, 1, 0, 0
         $r6 = M2_mpyi $r16, $r16
         $r22 = M2_accii $r22, killed $r2, 2
         $r7 = A2_tfrsi 12345678
@@ -27,6 +29,7 @@ body: |
         ; The anti-dependency on r23 between the first A2_add and the
         ; S2_asr_i_r was causing d11 to be renamed, while r22 remained
         ; unchanged. Check that the renaming of d11 does not happen.
+        ; CHECK: PSEUDO_PROBE 1, 1, 0, 0
         ; CHECK: d11
         $d0 = A2_tfrp killed $d11
         J2_call @check, implicit-def $d0, implicit-def $d1, implicit-def $d2, implicit $d0, implicit $d1, implicit $d2