[llvm] e7c9a6c - [SDAG] Don't move DBG_VALUE instructions after insertion point during scheduling (PR53243)

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2022-01-24T10:50:49+01:00
New Revision: e7c9a6cae09d99388d8384ca7c0fb5b24b353975

URL: https://github.com/llvm/llvm-project/commit/e7c9a6cae09d99388d8384ca7c0fb5b24b353975
DIFF: https://github.com/llvm/llvm-project/commit/e7c9a6cae09d99388d8384ca7c0fb5b24b353975.diff

LOG: [SDAG] Don't move DBG_VALUE instructions after insertion point during scheduling (PR53243)

EmitSchedule() shouldn't be touching instructions after the provided
insertion point. The change introduced in D83561 performs a scan to
the end of the block, and thus may move unrelated instructions. In
particular, this ends up moving instructions that have been produced
by FastISel and will later be deleted. Moving them means that more
instructions than intended are removed.

Fix this by stopping the iteration when the insertion point is
reached.

Fixes https://github.com/llvm/llvm-project/issues/53243.

Differential Revision: https://reviews.llvm.org/D117489

Added: 
    llvm/test/CodeGen/X86/pr53243-tail-call-fastisel.ll

Modified: 
    llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
index bec240d6c4d4..403f34573899 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
@@ -1057,12 +1057,13 @@ EmitSchedule(MachineBasicBlock::iterator &InsertPos) {
            "first terminator cannot be a debug value");
     for (MachineInstr &MI : make_early_inc_range(
              make_range(std::next(FirstTerm), InsertBB->end()))) {
+      // Only scan up to insertion point.
+      if (&MI == InsertPos)
+        break;
+
       if (!MI.isDebugValue())
         continue;
 
-      if (&MI == InsertPos)
-        InsertPos = std::prev(InsertPos->getIterator());
-
       // The DBG_VALUE was referencing a value produced by a terminator. By
       // moving the DBG_VALUE, the referenced value also needs invalidating.
       MI.getOperand(0).ChangeToRegister(0, false);

diff  --git a/llvm/test/CodeGen/X86/pr53243-tail-call-fastisel.ll b/llvm/test/CodeGen/X86/pr53243-tail-call-fastisel.ll
new file mode 100644
index 000000000000..333eff8fb008
--- /dev/null
+++ b/llvm/test/CodeGen/X86/pr53243-tail-call-fastisel.ll
@@ -0,0 +1,39 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -O0 -fast-isel -mtriple=x86_64-- < %s | FileCheck %s
+
+define void @test() {
+; CHECK-LABEL: test:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    jmp set_state at PLT # TAILCALL
+  tail call void @set_state()
+  call void @llvm.dbg.value(metadata i64 0, metadata !10, metadata !DIExpression()), !dbg !16
+  ret void
+}
+
+declare void @set_state()
+
+; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
+declare void @llvm.dbg.value(metadata, metadata, metadata) #0
+
+attributes #0 = { nofree nosync nounwind readnone speculatable willreturn }
+
+!llvm.module.flags = !{!0}
+!llvm.dbg.cu = !{!1}
+
+!0 = !{i32 2, !"Debug Info Version", i32 3}
+!1 = distinct !DICompileUnit(language: DW_LANG_Rust, file: !2, producer: "clang LLVM (rustc version 1.60.0-nightly (ec4bcaac4 2022-01-15))", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !3)
+!2 = !DIFile(filename: "src/lib.rs/@/bug.63e521cd-cgu.0", directory: "/tmp/rust-bug")
+!3 = !{!4}
+!4 = !DICompositeType(tag: DW_TAG_enumeration_type, name: "Option", file: !5, baseType: !6, size: 8, align: 8, flags: DIFlagEnumClass, elements: !7)
+!5 = !DIFile(filename: "<unknown>", directory: "")
+!6 = !DIBasicType(name: "u8", size: 8, encoding: DW_ATE_unsigned)
+!7 = !{!8, !9}
+!8 = !DIEnumerator(name: "None", value: 0)
+!9 = !DIEnumerator(name: "Some", value: 1)
+!10 = !DILocalVariable(name: "msg", arg: 2, scope: !11, file: !12, line: 689, type: !6)
+!11 = distinct !DISubprogram(name: "expect<()>", linkageName: "_ZN4core6option15Option$LT$T$GT$6expect17h9a574c18f194c213E", scope: !4, file: !12, line: 689, type: !13, scopeLine: 689, flags: DIFlagPrototyped, spFlags: DISPFlagLocalToUnit | DISPFlagDefinition | DISPFlagOptimized, unit: !1, templateParams: !15, retainedNodes: !15)
+!12 = !DIFile(filename: "/rustc/ec4bcaac450279b029f3480b8b8f1b82ab36a5eb/library/core/src/option.rs", directory: "", checksumkind: CSK_MD5, checksum: "4120c8557937a0772190a676ec193800")
+!13 = !DISubroutineType(types: !14)
+!14 = !{null, !4}
+!15 = !{}
+!16 = !DILocation(line: 0, scope: !11)