[llvm] 7398591 - [CodeGen] Add skipFunction() check to MachineFunctionSplitter (#166260)

[via llvm-commits]

Author: Grigory Pastukhov
Date: 2025-11-04T11:01:50-08:00
New Revision: 7398591148f4351b38404304d8e2acb80651aaf3

URL: https://github.com/llvm/llvm-project/commit/7398591148f4351b38404304d8e2acb80651aaf3
DIFF: https://github.com/llvm/llvm-project/commit/7398591148f4351b38404304d8e2acb80651aaf3.diff

LOG: [CodeGen] Add skipFunction() check to MachineFunctionSplitter (#166260)

MachineFunctionSplitter was missing a skipFunction() check, causing it
to incorrectly split functions that should be skipped (e.g., functions
with optnone attribute).

This patch adds an early skipFunction() check in runOnMachineFunction()
to ensure these functions are never split, regardless of profile data
availability or other splitting conditions.

Added: 
    llvm/test/CodeGen/Generic/machine-function-splitter-optnone.ll

Modified: 
    llvm/lib/CodeGen/MachineFunctionSplitter.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/MachineFunctionSplitter.cpp b/llvm/lib/CodeGen/MachineFunctionSplitter.cpp
index c31454a8affda..b5d3092ee84d8 100644
--- a/llvm/lib/CodeGen/MachineFunctionSplitter.cpp
+++ b/llvm/lib/CodeGen/MachineFunctionSplitter.cpp
@@ -129,6 +129,9 @@ static bool isColdBlock(const MachineBasicBlock &MBB,
 }
 
 bool MachineFunctionSplitter::runOnMachineFunction(MachineFunction &MF) {
+  if (skipFunction(MF.getFunction()))
+    return false;
+
   // Do not split functions when -basic-block-sections=all is specified.
   if (MF.getTarget().getBBSectionsType() == llvm::BasicBlockSection::All)
     return false;

diff  --git a/llvm/test/CodeGen/Generic/machine-function-splitter-optnone.ll b/llvm/test/CodeGen/Generic/machine-function-splitter-optnone.ll
new file mode 100644
index 0000000000000..67d2ad72ee2f4
--- /dev/null
+++ b/llvm/test/CodeGen/Generic/machine-function-splitter-optnone.ll
@@ -0,0 +1,50 @@
+; REQUIRES: x86-registered-target
+
+; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu -split-machine-functions -O0 -mfs-psi-cutoff=0 -mfs-count-threshold=10000 | FileCheck %s
+
+;; Check that functions with optnone attribute are not split.
+; CHECK-LABEL: foo_optnone:
+; CHECK-NOT:   .section .text.split.foo_optnone
+; CHECK-NOT:   foo_optnone.cold:
+; CHECK:       .LBB0_2:
+; CHECK:       .size   foo_optnone
+
+define void @foo_optnone(i1 zeroext %0) nounwind optnone noinline !prof !14 !section_prefix !15 {
+entry:
+  br i1 %0, label %hot, label %cold, !prof !17
+
+hot:
+  %1 = call i32 @bar()
+  br label %exit
+
+cold:
+  %2 = call i32 @baz()
+  br label %exit
+
+exit:
+  %3 = tail call i32 @qux()
+  ret void
+}
+
+declare i32 @bar()
+declare i32 @baz()
+declare i32 @qux()
+
+!llvm.module.flags = !{!0}
+!0 = !{i32 1, !"ProfileSummary", !1}
+!1 = !{!2, !3, !4, !5, !6, !7, !8, !9}
+!2 = !{!"ProfileFormat", !"InstrProf"}
+!3 = !{!"TotalCount", i64 10000}
+!4 = !{!"MaxCount", i64 10}
+!5 = !{!"MaxInternalCount", i64 1}
+!6 = !{!"MaxFunctionCount", i64 1000}
+!7 = !{!"NumCounts", i64 3}
+!8 = !{!"NumFunctions", i64 5}
+!9 = !{!"DetailedSummary", !10}
+!10 = !{!11, !12, !13}
+!11 = !{i32 10000, i64 100, i32 1}
+!12 = !{i32 999900, i64 100, i32 1}
+!13 = !{i32 999999, i64 1, i32 2}
+!14 = !{!"function_entry_count", i64 7000}
+!15 = !{!"function_section_prefix", !"hot"}
+!17 = !{!"branch_weights", i32 7000, i32 0}