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Fix PR14732 by handling all kinds of IMPLICIT_DEF live ranges.

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Most IMPLICIT_DEF instructions are removed by the ProcessImplicitDefs
pass, and a few are reinserted by PHIElimination when a PHI argument is
<undef>.

RegisterCoalescer was assuming that all IMPLICIT_DEF live ranges look
like those created by PHIElimination, and that their live range never
leaves the basic block.

The PR14732 test case does tricks with PHI nodes that causes a longer
IMPLICIT_DEF live range to appear. This happens very rarely, but
RegisterCoalescer should be able to handle it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171435 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2013-01-03 00:47:51 +00:00
parent 47990e9743
commit 251ed7f3e5
2 changed files with 167 additions and 8 deletions
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45
lib/CodeGen/RegisterCoalescer.cpp
View File

@ -1282,8 +1282,18 @@ class JoinVals {
// Value in the other live range that overlaps this def, if any. // Value in the other live range that overlaps this def, if any.
VNInfo *OtherVNI; VNInfo *OtherVNI;
// Is this value an IMPLICIT_DEF? // Is this value an IMPLICIT_DEF that can be erased?
bool IsImplicitDef; //
// IMPLICIT_DEF values should only exist at the end of a basic block that
// is a predecessor to a phi-value. These IMPLICIT_DEF instructions can be
// safely erased if they are overlapping a live value in the other live
// interval.
//
// Weird control flow graphs and incomplete PHI handling in
// ProcessImplicitDefs can very rarely create IMPLICIT_DEF values with
// longer live ranges. Such IMPLICIT_DEF values should be treated like
// normal values.
bool ErasableImplicitDef;
// True when the live range of this value will be pruned because of an // True when the live range of this value will be pruned because of an
// overlapping CR_Replace value in the other live range. // overlapping CR_Replace value in the other live range.
@ -1293,8 +1303,8 @@ class JoinVals {
bool PrunedComputed; bool PrunedComputed;
Val() : Resolution(CR_Keep), WriteLanes(0), ValidLanes(0), Val() : Resolution(CR_Keep), WriteLanes(0), ValidLanes(0),
RedefVNI(0), OtherVNI(0), IsImplicitDef(false), Pruned(false), RedefVNI(0), OtherVNI(0), ErasableImplicitDef(false),
PrunedComputed(false) {} Pruned(false), PrunedComputed(false) {}
bool isAnalyzed() const { return WriteLanes != 0; } bool isAnalyzed() const { return WriteLanes != 0; }
}; };
@ -1432,7 +1442,10 @@ JoinVals::analyzeValue(unsigned ValNo, JoinVals &Other) {
// An IMPLICIT_DEF writes undef values. // An IMPLICIT_DEF writes undef values.
if (DefMI->isImplicitDef()) { if (DefMI->isImplicitDef()) {
V.IsImplicitDef = true; // We normally expect IMPLICIT_DEF values to be live only until the end
// of their block. If the value is really live longer and gets pruned in
// another block, this flag is cleared again.
V.ErasableImplicitDef = true;
V.ValidLanes &= ~V.WriteLanes; V.ValidLanes &= ~V.WriteLanes;
} }
} }
@ -1485,7 +1498,22 @@ JoinVals::analyzeValue(unsigned ValNo, JoinVals &Other) {
// We have overlapping values, or possibly a kill of Other. // We have overlapping values, or possibly a kill of Other.
// Recursively compute assignments up the dominator tree. // Recursively compute assignments up the dominator tree.
Other.computeAssignment(V.OtherVNI->id, *this); Other.computeAssignment(V.OtherVNI->id, *this);
const Val &OtherV = Other.Vals[V.OtherVNI->id]; Val &OtherV = Other.Vals[V.OtherVNI->id];
// Check if OtherV is an IMPLICIT_DEF that extends beyond its basic block.
// This shouldn't normally happen, but ProcessImplicitDefs can leave such
// IMPLICIT_DEF instructions behind, and there is nothing wrong with it
// technically.
//
// WHen it happens, treat that IMPLICIT_DEF as a normal value, and don't try
// to erase the IMPLICIT_DEF instruction.
if (OtherV.ErasableImplicitDef && DefMI &&
DefMI->getParent() != Indexes->getMBBFromIndex(V.OtherVNI->def)) {
DEBUG(dbgs() << "IMPLICIT_DEF defined at " << V.OtherVNI->def
<< " extends into BB#" << DefMI->getParent()->getNumber()
<< ", keeping it.\n");
OtherV.ErasableImplicitDef = false;
}
// Allow overlapping PHI values. Any real interference would show up in a // Allow overlapping PHI values. Any real interference would show up in a
// predecessor, the PHI itself can't introduce any conflicts. // predecessor, the PHI itself can't introduce any conflicts.
@ -1794,7 +1822,8 @@ void JoinVals::pruneValues(JoinVals &Other,
// predecessors, so the instruction should simply go away once its value // predecessors, so the instruction should simply go away once its value
// has been replaced. // has been replaced.
Val &OtherV = Other.Vals[Vals[i].OtherVNI->id]; Val &OtherV = Other.Vals[Vals[i].OtherVNI->id];
bool EraseImpDef = OtherV.IsImplicitDef && OtherV.Resolution == CR_Keep; bool EraseImpDef = OtherV.ErasableImplicitDef &&
OtherV.Resolution == CR_Keep;
if (!Def.isBlock()) { if (!Def.isBlock()) {
// Remove <def,read-undef> flags. This def is now a partial redef. // Remove <def,read-undef> flags. This def is now a partial redef.
// Also remove <def,dead> flags since the joined live range will // Also remove <def,dead> flags since the joined live range will
@ -1843,7 +1872,7 @@ void JoinVals::eraseInstrs(SmallPtrSet<MachineInstr*, 8> &ErasedInstrs,
// If an IMPLICIT_DEF value is pruned, it doesn't serve a purpose any // If an IMPLICIT_DEF value is pruned, it doesn't serve a purpose any
// longer. The IMPLICIT_DEF instructions are only inserted by // longer. The IMPLICIT_DEF instructions are only inserted by
// PHIElimination to guarantee that all PHI predecessors have a value. // PHIElimination to guarantee that all PHI predecessors have a value.
if (!Vals[i].IsImplicitDef || !Vals[i].Pruned) if (!Vals[i].ErasableImplicitDef || !Vals[i].Pruned)
break; break;
// Remove value number i from LI. Note that this VNInfo is still present // Remove value number i from LI. Note that this VNInfo is still present
// in NewVNInfo, so it will appear as an unused value number in the final // in NewVNInfo, so it will appear as an unused value number in the final

130
test/CodeGen/X86/coalesce-implicitdef.ll Normal file
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@ -0,0 +1,130 @@
; RUN: llc < %s -verify-coalescing
; PR14732
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx10"
@c = common global i32 0, align 4
@b = common global i32 0, align 4
@a = common global i32 0, align 4
@d = common global i32 0, align 4
; This function creates an IMPLICIT_DEF with a long live range, even after
; ProcessImplicitDefs.
;
; The coalescer should be able to deal with all kinds of IMPLICIT_DEF live
; ranges, even if they are not common.
define void @f() nounwind uwtable ssp {
entry:
%i = alloca i32, align 4
br label %for.cond
for.cond: ; preds = %for.inc34, %entry
%i.0.load44 = phi i32 [ %inc35, %for.inc34 ], [ undef, %entry ]
%pi.0 = phi i32* [ %pi.4, %for.inc34 ], [ undef, %entry ]
%tobool = icmp eq i32 %i.0.load44, 0
br i1 %tobool, label %for.end36, label %for.body
for.body: ; preds = %for.cond
store i32 0, i32* @c, align 4, !tbaa !0
br label %for.body2
for.body2: ; preds = %for.body, %for.inc
%i.0.load45 = phi i32 [ %i.0.load44, %for.body ], [ 0, %for.inc ]
%tobool3 = icmp eq i32 %i.0.load45, 0
br i1 %tobool3, label %if.then10, label %if.then
if.then: ; preds = %for.body2
store i32 0, i32* %i, align 4, !tbaa !0
br label %for.body6
for.body6: ; preds = %if.then, %for.body6
store i32 0, i32* %i, align 4
br i1 true, label %for.body6, label %for.inc
if.then10: ; preds = %for.body2
store i32 1, i32* @b, align 4, !tbaa !0
ret void
for.inc: ; preds = %for.body6
br i1 undef, label %for.body2, label %if.end30
while.condthread-pre-split: ; preds = %label.loopexit, %while.condthread-pre-split.lr.ph.lr.ph, %for.inc27.backedge
%0 = phi i32 [ %inc28, %for.inc27.backedge ], [ %inc285863, %while.condthread-pre-split.lr.ph.lr.ph ], [ %inc2858, %label.loopexit ]
%inc2060 = phi i32 [ %inc20, %for.inc27.backedge ], [ %a.promoted.pre, %while.condthread-pre-split.lr.ph.lr.ph ], [ %inc20, %label.loopexit ]
br label %while.cond
while.cond: ; preds = %while.condthread-pre-split, %while.cond
%p2.1.in = phi i32* [ %pi.3.ph, %while.cond ], [ %i, %while.condthread-pre-split ]
%p2.1 = bitcast i32* %p2.1.in to i16*
br i1 %tobool19, label %while.end, label %while.cond
while.end: ; preds = %while.cond
%inc20 = add nsw i32 %inc2060, 1
%tobool21 = icmp eq i32 %inc2060, 0
br i1 %tobool21, label %for.inc27.backedge, label %if.then22
for.inc27.backedge: ; preds = %while.end, %if.then22
%inc28 = add nsw i32 %0, 1
store i32 %inc28, i32* @b, align 4, !tbaa !0
%tobool17 = icmp eq i32 %inc28, 0
br i1 %tobool17, label %for.inc27.if.end30.loopexit56_crit_edge, label %while.condthread-pre-split
if.then22: ; preds = %while.end
%1 = load i16* %p2.1, align 2, !tbaa !3
%tobool23 = icmp eq i16 %1, 0
br i1 %tobool23, label %for.inc27.backedge, label %label.loopexit
label.loopexit: ; preds = %if.then22
store i32 %inc20, i32* @a, align 4, !tbaa !0
%inc2858 = add nsw i32 %0, 1
store i32 %inc2858, i32* @b, align 4, !tbaa !0
%tobool1759 = icmp eq i32 %inc2858, 0
br i1 %tobool1759, label %if.end30, label %while.condthread-pre-split
for.inc27.if.end30.loopexit56_crit_edge: ; preds = %for.inc27.backedge
store i32 %inc20, i32* @a, align 4, !tbaa !0
br label %if.end30
if.end30: ; preds = %for.inc27.if.end30.loopexit56_crit_edge, %label.loopexit, %label.preheader, %for.inc
%i.0.load46 = phi i32 [ 0, %for.inc ], [ %i.0.load4669, %label.preheader ], [ %i.0.load4669, %label.loopexit ], [ %i.0.load4669, %for.inc27.if.end30.loopexit56_crit_edge ]
%pi.4 = phi i32* [ %i, %for.inc ], [ %pi.3.ph, %label.preheader ], [ %pi.3.ph, %label.loopexit ], [ %pi.3.ph, %for.inc27.if.end30.loopexit56_crit_edge ]
%2 = load i32* %pi.4, align 4, !tbaa !0
%tobool31 = icmp eq i32 %2, 0
br i1 %tobool31, label %for.inc34, label %label.preheader
for.inc34: ; preds = %if.end30
%inc35 = add nsw i32 %i.0.load46, 1
store i32 %inc35, i32* %i, align 4
br label %for.cond
for.end36: ; preds = %for.cond
store i32 1, i32* %i, align 4
%3 = load i32* @c, align 4, !tbaa !0
%tobool37 = icmp eq i32 %3, 0
br i1 %tobool37, label %label.preheader, label %land.rhs
land.rhs: ; preds = %for.end36
store i32 0, i32* @a, align 4, !tbaa !0
br label %label.preheader
label.preheader: ; preds = %for.end36, %if.end30, %land.rhs
%i.0.load4669 = phi i32 [ 1, %land.rhs ], [ %i.0.load46, %if.end30 ], [ 1, %for.end36 ]
%pi.3.ph = phi i32* [ %pi.0, %land.rhs ], [ %pi.4, %if.end30 ], [ %pi.0, %for.end36 ]
%4 = load i32* @b, align 4, !tbaa !0
%inc285863 = add nsw i32 %4, 1
store i32 %inc285863, i32* @b, align 4, !tbaa !0
%tobool175964 = icmp eq i32 %inc285863, 0
br i1 %tobool175964, label %if.end30, label %while.condthread-pre-split.lr.ph.lr.ph
while.condthread-pre-split.lr.ph.lr.ph: ; preds = %label.preheader
%.pr50 = load i32* @d, align 4, !tbaa !0
%tobool19 = icmp eq i32 %.pr50, 0
%a.promoted.pre = load i32* @a, align 4, !tbaa !0
br label %while.condthread-pre-split
}
!0 = metadata !{metadata !"int", metadata !1}
!1 = metadata !{metadata !"omnipotent char", metadata !2}
!2 = metadata !{metadata !"Simple C/C++ TBAA"}
!3 = metadata !{metadata !"short", metadata !1}