[llvm] Give ADJCALLSTACKUP and ADJCALLSTACKDOWN empty scheduling info (PR #152949)

[via llvm-commits]

https://github.com/AZero13 created https://github.com/llvm/llvm-project/pull/152949

Also label is isCodeGenOnly. Finally, we can keep the hasSideEffects, as there is no other way to do this.

>From edd13a8760252fab1801249b18b2e46bd0f8949e Mon Sep 17 00:00:00 2001
From: AZero13 <gfunni234 at gmail.com>
Date: Sun, 10 Aug 2025 20:52:31 -0400
Subject: [PATCH] Give ADJCALLSTACKUP and ADJCALLSTACKDOWN empty scheduling
 info

Also label is isCodeGenOnly. Finally, we can keep the hasSideEffects, as there is no other way to do this.
---
 llvm/lib/Target/ARM/ARMInstrInfo.td  | 12 +++++-------
 llvm/lib/Target/ARM/ARMInstrThumb.td | 11 +++++------
 2 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/llvm/lib/Target/ARM/ARMInstrInfo.td b/llvm/lib/Target/ARM/ARMInstrInfo.td
index 934ec52c6f1e4..79ba5ed1e8d43 100644
--- a/llvm/lib/Target/ARM/ARMInstrInfo.td
+++ b/llvm/lib/Target/ARM/ARMInstrInfo.td
@@ -2203,18 +2203,16 @@ def JUMPTABLE_TBH :
 PseudoInst<(outs), (ins cpinst_operand:$instid, cpinst_operand:$cpidx,
                         i32imm:$size), NoItinerary, []>;
 
-
-// FIXME: Marking these as hasSideEffects is necessary to prevent machine DCE
-// from removing one half of the matched pairs. That breaks PEI, which assumes
-// these will always be in pairs, and asserts if it finds otherwise. Better way?
-let Defs = [SP], Uses = [SP], hasSideEffects = 1 in {
+// We set Sched to empty list because we expect these instructions to simply get
+// removed in most cases.
+let Defs = [SP], Uses = [SP], hasSideEffects = 1, isCodeGenOnly = 1 in {
 def ADJCALLSTACKUP :
 PseudoInst<(outs), (ins i32imm:$amt1, i32imm:$amt2, pred:$p), NoItinerary,
-           [(ARMcallseq_end timm:$amt1, timm:$amt2)]>;
+           [(ARMcallseq_end timm:$amt1, timm:$amt2)]>, Sched<[]>;
 
 def ADJCALLSTACKDOWN :
 PseudoInst<(outs), (ins i32imm:$amt, i32imm:$amt2, pred:$p), NoItinerary,
-           [(ARMcallseq_start timm:$amt, timm:$amt2)]>;
+           [(ARMcallseq_start timm:$amt, timm:$amt2)]>, Sched<[]>;
 }
 
 def HINT : AI<(outs), (ins imm0_239:$imm), MiscFrm, NoItinerary,
diff --git a/llvm/lib/Target/ARM/ARMInstrThumb.td b/llvm/lib/Target/ARM/ARMInstrThumb.td
index e38cafdf55c46..b3dfbb9c4d281 100644
--- a/llvm/lib/Target/ARM/ARMInstrThumb.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb.td
@@ -297,19 +297,18 @@ def non_imm32 : PatLeaf<(i32 GPR), [{ return !isa<ConstantSDNode>(N); }]>;
 //  Miscellaneous Instructions.
 //
 
-// FIXME: Marking these as hasSideEffects is necessary to prevent machine DCE
-// from removing one half of the matched pairs. That breaks PEI, which assumes
-// these will always be in pairs, and asserts if it finds otherwise. Better way?
-let Defs = [SP], Uses = [SP], hasSideEffects = 1 in {
+// We set Sched to empty list because we expect these instructions to simply get
+// removed in most cases.
+let Defs = [SP], Uses = [SP], hasSideEffects = 1, isCodeGenOnly = 1 in {
 def tADJCALLSTACKUP :
   PseudoInst<(outs), (ins i32imm:$amt1, i32imm:$amt2), NoItinerary,
              [(ARMcallseq_end imm:$amt1, imm:$amt2)]>,
-            Requires<[IsThumb, IsThumb1Only]>;
+            Requires<[IsThumb, IsThumb1Only]>, Sched<[]>;
 
 def tADJCALLSTACKDOWN :
   PseudoInst<(outs), (ins i32imm:$amt, i32imm:$amt2), NoItinerary,
              [(ARMcallseq_start imm:$amt, imm:$amt2)]>,
-            Requires<[IsThumb, IsThumb1Only]>;
+            Requires<[IsThumb, IsThumb1Only]>, Sched<[]>;
 }
 
 class T1SystemEncoding<bits<8> opc>