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Place the lowered phi instruction(s) before the DEBUG_VALUE entry

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When a phi node is finally lowered to a machine instruction it is
important that the lowered "load" instruction is placed before the
associated DEBUG_VALUE entry describing the value loaded.

Renamed the existing SkipPHIsAndLabels to SkipPHIsLabelsAndDebug to
more fully describe that it also skips debug entries. Then used the
"new" function SkipPHIsAndLabels when the debug information should not
be skipped when placing the lowered "load" instructions so that it is
placed before the debug entries.

Differential Revision: https://reviews.llvm.org/D23760 


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281727 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Keith Walker 2016-09-16 14:07:29 +00:00
parent ffabbc5291
commit 7435b28542
8 changed files with 102 additions and 8 deletions
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9
include/llvm/CodeGen/MachineBasicBlock.h
View File

@ -455,10 +455,15 @@ public:
iterator getFirstNonPHI();
/// Return the first instruction in MBB after I that is not a PHI or a label.
/// This is the correct point to insert copies at the beginning of a basic
/// block.
/// This is the correct point to insert lowered copies at the beginning of a
/// basic block that must be before any debugging information.
iterator SkipPHIsAndLabels(iterator I);
/// Return the first instruction in MBB after I that is not a PHI, label or
/// debug. This is the correct point to insert copies at the beginning of a
/// basic block.
iterator SkipPHIsLabelsAndDebug(iterator I);
/// Returns an iterator to the first terminator instruction of this basic
/// block. If a terminator does not exist, it returns end().
iterator getFirstTerminator();

2
lib/CodeGen/InlineSpiller.cpp
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@ -377,7 +377,7 @@ bool InlineSpiller::hoistSpillInsideBB(LiveInterval &SpillLI,
MachineBasicBlock *MBB = LIS.getMBBFromIndex(SrcVNI->def);
MachineBasicBlock::iterator MII;
if (SrcVNI->isPHIDef())
MII = MBB->SkipPHIsAndLabels(MBB->begin());
MII = MBB->SkipPHIsLabelsAndDebug(MBB->begin());
else {
MachineInstr *DefMI = LIS.getInstructionFromIndex(SrcVNI->def);
assert(DefMI && "Defining instruction disappeared");

2
lib/CodeGen/LiveDebugVariables.cpp
View File

@ -951,7 +951,7 @@ findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
while (!(MI = LIS.getInstructionFromIndex(Idx))) {
// We've reached the beginning of MBB.
if (Idx == Start) {
MachineBasicBlock::iterator I = MBB->SkipPHIsAndLabels(MBB->begin());
MachineBasicBlock::iterator I = MBB->SkipPHIsLabelsAndDebug(MBB->begin());
return I;
}
Idx = Idx.getPrevIndex();

15
lib/CodeGen/MachineBasicBlock.cpp
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@ -148,13 +148,26 @@ MachineBasicBlock::iterator MachineBasicBlock::getFirstNonPHI() {
MachineBasicBlock::iterator
MachineBasicBlock::SkipPHIsAndLabels(MachineBasicBlock::iterator I) {
iterator E = end();
while (I != E && (I->isPHI() || I->isPosition()))
++I;
// FIXME: This needs to change if we wish to bundle labels
// inside the bundle.
assert((I == E || !I->isInsideBundle()) &&
"First non-phi / non-label instruction is inside a bundle!");
return I;
}
MachineBasicBlock::iterator
MachineBasicBlock::SkipPHIsLabelsAndDebug(MachineBasicBlock::iterator I) {
iterator E = end();
while (I != E && (I->isPHI() || I->isPosition() || I->isDebugValue()))
++I;
// FIXME: This needs to change if we wish to bundle labels / dbg_values
// inside the bundle.
assert((I == E || !I->isInsideBundle()) &&
"First non-phi / non-label instruction is inside a bundle!");
"First non-phi / non-label / non-debug "
"instruction is inside a bundle!");
return I;
}

3
lib/CodeGen/PHIEliminationUtils.cpp
View File

@ -54,6 +54,7 @@ llvm::findPHICopyInsertPoint(MachineBasicBlock* MBB, MachineBasicBlock* SuccMBB,
++InsertPoint;
}
// Make sure the copy goes after any phi nodes however.
// Make sure the copy goes after any phi nodes but before
// any debug nodes.
return MBB->SkipPHIsAndLabels(InsertPoint);
}

2
lib/CodeGen/SplitKit.cpp
View File

@ -675,7 +675,7 @@ SlotIndex SplitEditor::leaveIntvAtTop(MachineBasicBlock &MBB) {
}
VNInfo *VNI = defFromParent(0, ParentVNI, Start, MBB,
MBB.SkipPHIsAndLabels(MBB.begin()));
MBB.SkipPHIsLabelsAndDebug(MBB.begin()));
RegAssign.insert(Start, VNI->def, OpenIdx);
DEBUG(dump());
return VNI->def;

2
lib/Target/PowerPC/PPCEarlyReturn.cpp
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@ -58,7 +58,7 @@ protected:
bool Changed = false;
MachineBasicBlock::iterator I = ReturnMBB.begin();
I = ReturnMBB.SkipPHIsAndLabels(I);
I = ReturnMBB.SkipPHIsLabelsAndDebug(I);
// The block must be essentially empty except for the blr.
if (I == ReturnMBB.end() ||

75
test/CodeGen/AArch64/phi-dbg.ll Normal file
View File

@ -0,0 +1,75 @@
; RUN: llc -O0 %s -mtriple=aarch64 -o - | FileCheck %s
; Test that a DEBUG_VALUE node is create for variable c after the phi has been
; converted to a ldr. The DEBUG_VALUE must be *after* the ldr and not before it.
; Created from the C code, compiled with -O0 -g and then passed through opt -mem2reg:
;
; int func(int a)
; {
; int c = 1;
; if (a < 0 ) {
; c = 12;
; }
; return c;
; }
;
; Function Attrs: nounwind
define i32 @func(i32) #0 !dbg !8 {
call void @llvm.dbg.value(metadata i32 %0, i64 0, metadata !12, metadata !13), !dbg !14
call void @llvm.dbg.value(metadata i32 1, i64 0, metadata !15, metadata !13), !dbg !16
%2 = icmp slt i32 %0, 0, !dbg !17
br i1 %2, label %3, label %4, !dbg !19
; <label>:3: ; preds = %1
call void @llvm.dbg.value(metadata i32 12, i64 0, metadata !15, metadata !13), !dbg !16
br label %4, !dbg !20
; <label>:4: ; preds = %3, %1
%.0 = phi i32 [ 12, %3 ], [ 1, %1 ]
; CHECK: ldr w[[REG:[0-9]+]], [sp, #8]
; CHECK-NEXT: .Ltmp
call void @llvm.dbg.value(metadata i32 %.0, i64 0, metadata !15, metadata !13), !dbg !16
; CHECK-NEXT: //DEBUG_VALUE: func:c <- %W[[REG]]
%5 = add nsw i32 %.0, %0, !dbg !22
call void @llvm.dbg.value(metadata i32 %5, i64 0, metadata !15, metadata !13), !dbg !16
ret i32 %5, !dbg !23
}
; Function Attrs: nounwind readnone
declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
; Function Attrs: nounwind readnone
declare void @llvm.dbg.value(metadata, i64, metadata, metadata) #1
attributes #0 = { nounwind }
attributes #1 = { nounwind readnone }
!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 = distinct !DISubprogram(name: "func", scope: !1, file: !1, line: 1, type: !9, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
!9 = !DISubroutineType(types: !10)
!10 = !{!11, !11}
!11 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
!12 = !DILocalVariable(name: "a", arg: 1, scope: !8, file: !1, line: 1, type: !11)
!13 = !DIExpression()
!14 = !DILocation(line: 1, column: 14, scope: !8)
!15 = !DILocalVariable(name: "c", scope: !8, file: !1, line: 3, type: !11)
!16 = !DILocation(line: 3, column: 13, scope: !8)
!17 = !DILocation(line: 4, column: 15, scope: !18)
!18 = distinct !DILexicalBlock(scope: !8, file: !1, line: 4, column: 13)
!19 = !DILocation(line: 4, column: 13, scope: !8)
!20 = !DILocation(line: 6, column: 9, scope: !21)
!21 = distinct !DILexicalBlock(scope: !18, file: !1, line: 4, column: 21)
!22 = !DILocation(line: 7, column: 4, scope: !8)
!23 = !DILocation(line: 8, column: 9, scope: !8)