[MergedLoadStoreMotion] Fix a debug invariant bug in mergeStores

Summary:
MergedLoadStoreMotion::mergeStores is using some heuristics
to limit the amount of stores that it tries to sink (see
MagicCompileTimeControl in MergedLoadStoreMotion.cpp). The
heuristic involves counting the number of instructions in
one of the basic blocks that is part of the transformation.

We now ignore dbg intrinsics when counting instruction for
the MagicCompileTimeControl heuristic. This to make sure that
the amount of stores that are sunk doesn't depend on the amount
of debug information (if -g is used or not).

Reviewers: Gerolf, davide, majnemer

Reviewed By: davide

Subscribers: dberlin, bjope, aprantl, JDevlieghere, llvm-commits

Differential Revision: https://reviews.llvm.org/D46600

llvm-svn: 331852

2 files changed, 158 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp b/llvm/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp
index cbed9a97c56..35e341f39a7 100644
--- a/llvm/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp
+++ b/llvm/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp
@@ -285,7 +285,8 @@ bool MergedLoadStoreMotion::mergeStores(BasicBlock *T) {
     return false; // No. More than 2 predecessors.
 
   // #Instructions in Succ1 for Compile Time Control
-  int Size1 = Pred1->size();
+  int Size1 = std::distance(Pred1->instructionsWithoutDebug().begin(),
+                            Pred1->instructionsWithoutDebug().end());
   int NStores = 0;
 
   for (BasicBlock::reverse_iterator RBI = Pred0->rbegin(), RBE = Pred0->rend();
diff --git a/llvm/test/Transforms/InstMerge/st_sink_debuginvariant.ll b/llvm/test/Transforms/InstMerge/st_sink_debuginvariant.ll
new file mode 100644
index 00000000000..4a2d8040726
--- /dev/null
+++ b/llvm/test/Transforms/InstMerge/st_sink_debuginvariant.ll
@@ -0,0 +1,156 @@
+; RUN: opt < %s -S -mldst-motion -o - | FileCheck %s
+; RUN: opt < %s -S -strip-debug -mldst-motion -o - | FileCheck %s
+
+; Verify that the amount of stores that are sunk is invariant regarding debug
+; info.  This used to fail due to including dbg.value instructions when
+; calculating the size of a basic block for the "MagicCompileTimeControl"
+; check in MergedLoadStoreMotion::mergeStores.
+
+; CHECK-LABEL: return:
+; CHECK-NEXT:    %.sink = phi i16 [ 5, %if.end ], [ 6, %if.then ]
+; CHECK-NEXT:    %0 = getelementptr inbounds %struct.S0, %struct.S0* %agg.result, i16 0, i32 0
+; CHECK-NEXT:    store i16 %.sink, i16* %0
+; CHECK-NEXT:    %1 = getelementptr inbounds %struct.S0, %struct.S0* %agg.result, i16 0, i32 1
+; CHECK-NEXT:    store i16 0, i16* %1
+; CHECK-NEXT:    ret void
+
+%struct.S0 = type { i16, i16 }
+
+@g_173 = dso_local local_unnamed_addr global i16 0, !dbg !0
+
+; Function Attrs: noinline norecurse nounwind
+define dso_local void @func_34(%struct.S0* noalias sret %agg.result) local_unnamed_addr #0 !dbg !11 {
+entry:
+  br i1 undef, label %if.end, label %if.then, !dbg !18
+
+if.then:                                          ; preds = %entry
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i16 5, metadata !19, metadata !DIExpression()), !dbg !22
+  %l_303.sroa.0.0..sroa_idx = getelementptr inbounds %struct.S0, %struct.S0* %agg.result, i16 0, i32 0, !dbg !23
+  store i16 6, i16* %l_303.sroa.0.0..sroa_idx, !dbg !23
+  %l_303.sroa.2.0..sroa_idx1 = getelementptr inbounds %struct.S0, %struct.S0* %agg.result, i16 0, i32 1, !dbg !23
+  store i16 0, i16* %l_303.sroa.2.0..sroa_idx1, !dbg !23
+  br label %return, !dbg !24
+
+if.end:                                           ; preds = %entry
+  %f037 = getelementptr inbounds %struct.S0, %struct.S0* %agg.result, i16 0, i32 0, !dbg !25
+  store i16 5, i16* %f037, !dbg !25
+  %f138 = getelementptr inbounds %struct.S0, %struct.S0* %agg.result, i16 0, i32 1, !dbg !25
+  store i16 0, i16* %f138, !dbg !25
+  store i16 0, i16* @g_173, !dbg !27
+  br label %return, !dbg !28
+
+return:                                           ; preds = %if.end, %if.then
+  ret void, !dbg !29
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.value(metadata, metadata, metadata) #1
+
+attributes #0 = { noinline norecurse nounwind }
+attributes #1 = { nounwind readnone speculatable }
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!7, !8, !9}
+!llvm.ident = !{!10}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "g_173", scope: !2, file: !3, line: 7, type: !6, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 7.0.0 (x)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5)
+!3 = !DIFile(filename: "csmith11794002068761.c", directory: "")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIBasicType(name: "int", size: 16, encoding: DW_ATE_signed)
+!7 = !{i32 2, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{i32 1, !"wchar_size", i32 1}
+!10 = !{!"clang version 7.0.0 (x)"}
+!11 = distinct !DISubprogram(name: "func_34", scope: !3, file: !3, line: 16, type: !12, isLocal: false, isDefinition: true, scopeLine: 16, isOptimized: false, unit: !2, retainedNodes: !4)
+!12 = !DISubroutineType(types: !13)
+!13 = !{!14}
+!14 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "S0", file: !3, line: 2, size: 32, elements: !15)
+!15 = !{!16, !17}
+!16 = !DIDerivedType(tag: DW_TAG_member, name: "f0", scope: !14, file: !3, line: 3, baseType: !6, size: 16)
+!17 = !DIDerivedType(tag: DW_TAG_member, name: "f1", scope: !14, file: !3, line: 4, baseType: !6, size: 16, offset: 16)
+!18 = !DILocation(line: 18, column: 7, scope: !11)
+!19 = !DILocalVariable(name: "left", scope: !20, file: !3, line: 23, type: !6)
+!20 = distinct !DILexicalBlock(scope: !21, file: !3, line: 18, column: 14)
+!21 = distinct !DILexicalBlock(scope: !11, file: !3, line: 18, column: 7)
+!22 = !DILocation(line: 23, column: 9, scope: !20)
+!23 = !DILocation(line: 26, column: 12, scope: !20)
+!24 = !DILocation(line: 26, column: 5, scope: !20)
+!25 = !DILocation(line: 29, column: 23, scope: !26)
+!26 = distinct !DILexicalBlock(scope: !11, file: !3, line: 28, column: 3)
+!27 = !DILocation(line: 30, column: 11, scope: !26)
+!28 = !DILocation(line: 31, column: 5, scope: !26)
+!29 = !DILocation(line: 33, column: 1, scope: !11)