CodeGen: ignore DEBUG_VALUE nodes in KILL tagging

DEBUG_VALUE nodes do not take part in code generation.  Ignore them when
performing KILL updates.  Addresses PR23486.

llvm-svn: 237211

Author: compnerd

llvm/lib/CodeGen/ScheduleDAGInstrs.cpp

@@ -1115,6 +1115,12 @@ static void toggleBundleKillFlag(MachineInstr *MI, unsigned Reg,
       if (!MO->isReg() || MO->isDef() || Reg != MO->getReg())
         continue;
 
+      // DEBUG_VALUE nodes do not contribute to code generation and should
+      // always be ignored.  Failure to do so may result in trying to modify
+      // KILL flags on DEBUG_VALUE nodes, which is distressing.
+      if (MO->isDebug())
+        continue;
+
       // If the register has the internal flag then it could be killing an
       // internal def of the register.  In this case, just skip.  We only want
       // to toggle the flag on operands visible outside the bundle.

llvm/test/CodeGen/ARM/sched-it-debug-nodes.ll

@@ -0,0 +1,88 @@
+; RUN: llc -mtriple thumbv7 -print-before=post-RA-sched -print-after=post-RA-sched %s -o /dev/null 2>&1 | FileCheck %s
+
+; ModuleID = '<stdin>'
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "thumbv7"
+
+%struct.s = type opaque
+
+; Function Attrs: nounwind
+define arm_aapcscc i32 @f(%struct.s* %s, i32 %u, i8* %b, i32 %n) #0 {
+entry:
+  tail call void @llvm.dbg.value(metadata %struct.s* %s, i64 0, metadata !19, metadata !28), !dbg !29
+  tail call void @llvm.dbg.value(metadata i32 %u, i64 0, metadata !20, metadata !28), !dbg !29
+  tail call void @llvm.dbg.value(metadata i8* %b, i64 0, metadata !21, metadata !28), !dbg !29
+  tail call void @llvm.dbg.value(metadata i32 %n, i64 0, metadata !22, metadata !28), !dbg !29
+  %cmp = icmp ult i32 %n, 4, !dbg !30
+  br i1 %cmp, label %return, label %if.end, !dbg !32
+
+if.end:                                           ; preds = %entry
+  tail call arm_aapcscc void @g(%struct.s* %s, i8* %b, i32 %n) #3, !dbg !33
+  br label %return, !dbg !34
+
+return:                                           ; preds = %entry, %if.end
+  %retval.0 = phi i32 [ 0, %if.end ], [ -1, %entry ]
+  ret i32 %retval.0, !dbg !35
+}
+
+; NOTE: This is checking that the register in the DEBUG_VALUE node is not
+; accidentally being marked as KILL.  The DBG_VALUE node gets introduced in
+; If-Conversion, and gets bundled into the IT block.  The Post RA Scheduler
+; attempts to schedule the Machine Instr, and tries to tag the register in the
+; debug value as KILL'ed, resulting in a DEBUG_VALUE node changing codegen!  (or
+; hopefully, triggering an assert).
+
+; CHECK: BUNDLE %ITSTATE<imp-def,dead>
+; CHECK:  * DBG_VALUE %R1, %noreg, !"u"
+; CHECK-NOT:  * DBG_VALUE %R1<kill>, %noreg, !"u"
+
+declare arm_aapcscc void @g(%struct.s*, i8*, i32) #1
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #2
+
+attributes #0 = { nounwind "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-realign-stack" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-realign-stack" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #2 = { nounwind readnone }
+attributes #3 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!23, !24, !25, !26}
+!llvm.ident = !{!27}
+
+!0 = !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.7.0  (llvm/trunk 237059)", isOptimized: true, runtimeVersion: 0, emissionKind: 1, enums: !2, retainedTypes: !2, subprograms: !3, globals: !2, imports: !2)
+!1 = !DIFile(filename: "<stdin>", directory: "/Users/compnerd/Source/llvm")
+!2 = !{}
+!3 = !{!4}
+!4 = !DISubprogram(name: "f", scope: !5, file: !5, line: 9, type: !6, isLocal: false, isDefinition: true, scopeLine: 9, flags: DIFlagPrototyped, isOptimized: true, function: i32 (%struct.s*, i32, i8*, i32)* @f, variables: !18)
+!5 = !DIFile(filename: "<stdin>", directory: "/Users/compnerd/Source/llvm")
+!6 = !DISubroutineType(types: !7)
+!7 = !{!8, !9, !12, !13, !17}
+!8 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!9 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !10, size: 32, align: 32)
+!10 = !DIDerivedType(tag: DW_TAG_typedef, name: "s", file: !5, line: 5, baseType: !11)
+!11 = !DICompositeType(tag: DW_TAG_structure_type, name: "s", file: !5, line: 5, flags: DIFlagFwdDecl)
+!12 = !DIBasicType(name: "unsigned int", size: 32, align: 32, encoding: DW_ATE_unsigned)
+!13 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !14, size: 32, align: 32)
+!14 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !15)
+!15 = !DIDerivedType(tag: DW_TAG_typedef, name: "uint8_t", file: !5, line: 2, baseType: !16)
+!16 = !DIBasicType(name: "unsigned char", size: 8, align: 8, encoding: DW_ATE_unsigned_char)
+!17 = !DIDerivedType(tag: DW_TAG_typedef, name: "size_t", file: !5, line: 3, baseType: !12)
+!18 = !{!19, !20, !21, !22}
+!19 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "s", arg: 1, scope: !4, file: !5, line: 9, type: !9)
+!20 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "u", arg: 2, scope: !4, file: !5, line: 9, type: !12)
+!21 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "b", arg: 3, scope: !4, file: !5, line: 9, type: !13)
+!22 = !DILocalVariable(tag: DW_TAG_arg_variable, name: "n", arg: 4, scope: !4, file: !5, line: 9, type: !17)
+!23 = !{i32 2, !"Dwarf Version", i32 4}
+!24 = !{i32 2, !"Debug Info Version", i32 3}
+!25 = !{i32 1, !"wchar_size", i32 4}
+!26 = !{i32 1, !"min_enum_size", i32 4}
+!27 = !{!"clang version 3.7.0  (llvm/trunk 237059)"}
+!28 = !DIExpression()
+!29 = !DILocation(line: 9, scope: !4)
+!30 = !DILocation(line: 10, scope: !31)
+!31 = distinct !DILexicalBlock(scope: !4, file: !5, line: 10)
+!32 = !DILocation(line: 10, scope: !4)
+!33 = !DILocation(line: 13, scope: !4)
+!34 = !DILocation(line: 14, scope: !4)
+!35 = !DILocation(line: 15, scope: !4)