[llvm] 75188b0 - [PHIEliminate] Move dbg values after phi and label
Jeremy Morse via llvm-commits
llvm-commits at lists.llvm.org
Thu Jan 16 03:59:24 PST 2020
Author: Chris Ye
Date: 2020-01-16T11:58:09Z
New Revision: 75188b01e9af3a89639d84be912f84610d6885ba
URL: https://github.com/llvm/llvm-project/commit/75188b01e9af3a89639d84be912f84610d6885ba
DIFF: https://github.com/llvm/llvm-project/commit/75188b01e9af3a89639d84be912f84610d6885ba.diff
LOG: [PHIEliminate] Move dbg values after phi and label
If there are DBG_VALUEs between phi and label (after phi and before label),
DBG_VALUE will block PHI lowering after the LABEL. Moving all DBG_VALUEs
after Labels in the function ScheduleDAGSDNodes::EmitSchedule to avoid
impacting PHI lowering.
before:
PHI
DBG_VALUE
LABEL
after: (move DBG_VALUE after label)
PHI
LABEL
DBG_VALUE
then: (phi lowering after label)
LABEL
COPY
DBG_VALUE
Fixes the issue: https://bugs.llvm.org/show_bug.cgi?id=43859
Differential Revision: https://reviews.llvm.org/D70597
Added:
llvm/test/CodeGen/X86/dbg-changes-codegen-phi-elimination.ll
Modified:
llvm/lib/CodeGen/MachineVerifier.cpp
llvm/lib/CodeGen/PHIElimination.cpp
llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
Removed:
################################################################################
diff --git a/llvm/lib/CodeGen/MachineVerifier.cpp b/llvm/lib/CodeGen/MachineVerifier.cpp
index 6c0402df8489..24fb330bafdd 100644
--- a/llvm/lib/CodeGen/MachineVerifier.cpp
+++ b/llvm/lib/CodeGen/MachineVerifier.cpp
@@ -273,6 +273,7 @@ namespace {
void markReachable(const MachineBasicBlock *MBB);
void calcRegsPassed();
void checkPHIOps(const MachineBasicBlock &MBB);
+ void checkPHIDbg(const MachineBasicBlock &MBB);
void calcRegsRequired();
void verifyLiveVariables();
@@ -2262,11 +2263,31 @@ void MachineVerifier::checkPHIOps(const MachineBasicBlock &MBB) {
}
}
+// Check there must be no DBG_VALUEs between PHIs and LABELs, so that
+// the PHIs could lower after LABELs successfully without dbg barriers.
+void MachineVerifier::checkPHIDbg(const MachineBasicBlock &MBB) {
+
+ // Quick exit for basic blocks without PHIs.
+ if (MBB.empty() || !MBB.front().isPHI())
+ return;
+
+ MachineBasicBlock &MBB2 = const_cast<MachineBasicBlock &>(MBB);
+ MachineBasicBlock::iterator LastPHIIt =
+ std::prev(MBB2.SkipPHIsAndLabels(MBB2.begin()));
+ // Backward to skip debug if the lastPHIIt is DBG_VALUE, the LastPHIIt
+ // should be the same if no DBG_VALUEs between PHIs and LABELs.
+ if (LastPHIIt != skipDebugInstructionsBackward(
+ std::prev(MBB2.SkipPHIsLabelsAndDebug(MBB2.begin())), MBB2.begin()))
+ report("Unexpected DBG_VALUEs between PHI and LABEL", &MBB2);
+}
+
void MachineVerifier::visitMachineFunctionAfter() {
calcRegsPassed();
- for (const MachineBasicBlock &MBB : *MF)
+ for (const MachineBasicBlock &MBB : *MF) {
checkPHIOps(MBB);
+ checkPHIDbg(MBB);
+ }
// Now check liveness info if available
calcRegsRequired();
diff --git a/llvm/lib/CodeGen/PHIElimination.cpp b/llvm/lib/CodeGen/PHIElimination.cpp
index 4dd4c4b1084e..1ed479db54d3 100644
--- a/llvm/lib/CodeGen/PHIElimination.cpp
+++ b/llvm/lib/CodeGen/PHIElimination.cpp
@@ -210,6 +210,11 @@ bool PHIElimination::EliminatePHINodes(MachineFunction &MF,
MachineBasicBlock::iterator LastPHIIt =
std::prev(MBB.SkipPHIsAndLabels(MBB.begin()));
+ assert((LastPHIIt == skipDebugInstructionsBackward(
+ std::prev(MBB.SkipPHIsLabelsAndDebug(MBB.begin())),
+ MBB.begin())) &&
+ "There must be no DBG_VALUEs between PHI and LABEL");
+
while (MBB.front().isPHI())
LowerPHINode(MBB, LastPHIIt);
diff --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
index 0e4d783e3505..a911aecb352e 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
@@ -929,10 +929,12 @@ EmitSchedule(MachineBasicBlock::iterator &InsertPos) {
}
}
- // Insert all the dbg_values which have not already been inserted in source
+ // Insert all the DBG_VALUEs which have not already been inserted in source
// order sequence.
if (HasDbg) {
- MachineBasicBlock::iterator BBBegin = BB->getFirstNonPHI();
+ // Always place DBG_VALUEs after all other special start-of-block
+ // instructions, to avoid debug data hiding start-of-block instructions.
+ MachineBasicBlock::iterator BBBegin = BB->SkipPHIsAndLabels(BB->begin());
// Sort the source order instructions and use the order to insert debug
// values. Use stable_sort so that DBG_VALUEs are inserted in the same order
diff --git a/llvm/test/CodeGen/X86/dbg-changes-codegen-phi-elimination.ll b/llvm/test/CodeGen/X86/dbg-changes-codegen-phi-elimination.ll
new file mode 100644
index 000000000000..0077673596c3
--- /dev/null
+++ b/llvm/test/CodeGen/X86/dbg-changes-codegen-phi-elimination.ll
@@ -0,0 +1,66 @@
+; RUN: llc -O0 %s -mtriple=x86_64 -stop-after=phi-node-elimination -verify-machineinstrs -o - | FileCheck %s
+
+; Test that the DBG_VALUE must be after PHI and label, the PHI is converted to
+; a copy and lower after Label. The DBG_VALUE should not impact PHI lowering.
+; before:
+; phi
+; dbg_value
+; label
+; after:
+; LABEL
+; COPY
+; DBG_VALUE
+; Fix the issue: https://bugs.llvm.org/show_bug.cgi?id=43859
+
+define i32 @func(i32 %a0) personality void ()* @personality !dbg !9 {
+bb1:
+ %v = icmp slt i32 %a0, 0
+ br i1 %v, label %bb2, label %bb3
+
+bb2:
+ br label %bb3
+
+bb3:
+; CHECK: bb.2.bb3:
+; CHECK: EH_LABEL
+; CHECK-NEXT: %0:gr32 = COPY %7
+; CHECK-NEXT: DBG_VALUE %0
+ %0 = phi i32 [ 2, %bb2 ], [ 1, %bb1 ]
+ call void @llvm.dbg.value(metadata i32 %0, metadata !8, metadata !DIExpression()), !dbg !13
+ invoke void @foo() to label %end unwind label %lpad
+
+end:
+ ret i32 %0
+
+lpad:
+ %1 = landingpad { i8*, i32 }
+ cleanup
+ unreachable
+}
+
+declare void @foo()
+
+declare void @personality()
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+!llvm.ident = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "a.c", directory: "/tmp")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 4}
+!6 = !{i32 1, !"min_enum_size", i32 4}
+!7 = !{!"clang"}
+!8 = !DILocalVariable(name: "c", scope: !9, file: !1, line: 3, type: !12)
+!9 = distinct !DISubprogram(name: "func", scope: !1, file: !1, line: 1, type: !10, scopeLine: 2, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !2)
+!10 = !DISubroutineType(types: !11)
+!11 = !{!12, !12}
+!12 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!13 = !DILocation(line: 3, column: 13, scope: !9)
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