Fix PR3149. If an early clobber def is a physical register and it is tied to an input operand, it effectively extends the live range of the physical register. Currently we do not have a good way to represent this.
172 %ECX<def> = MOV32rr %reg1039<kill>
180 INLINEASM <es:subl $5,$1
sbbl $3,$0>, 10, %EAX<def>, 14, %ECX<earlyclobber,def>, 9, %EAX<kill>,
36, <fi#0>, 1, %reg0, 0, 9, %ECX<kill>, 36, <fi#1>, 1, %reg0, 0
188 %EAX<def> = MOV32rr %EAX<kill>
196 %ECX<def> = MOV32rr %ECX<kill>
204 %ECX<def> = MOV32rr %ECX<kill>
212 %EAX<def> = MOV32rr %EAX<kill>
220 %EAX<def> = MOV32rr %EAX
228 %reg1039<def> = MOV32rr %ECX<kill>
The early clobber operand ties ECX input to the ECX def.
The live interval of ECX is represented as this:
%reg20,inf = [46,47:1)[174,230:0) 0@174-(230) 1@46-(47)
The right way to represent this is something like
%reg20,inf = [46,47:2)[174,182:1)[181:230:0) 0@174-(182) 1@181-230 @2@46-(47)
Of course that won't work since that means overlapping live ranges defined by two val#.
The workaround for now is to add a bit to val# which says the val# is redefined by a early clobber def somewhere. This prevents the move at 228 from being optimized away by SimpleRegisterCoalescing::AdjustCopiesBackFrom.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61259 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 52b57d6..1900c1a 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -360,6 +360,7 @@
mi->getOpcode() == TargetInstrInfo::INSERT_SUBREG ||
tii_->isMoveInstr(*mi, SrcReg, DstReg))
CopyMI = mi;
+ // Earlyclobbers move back one.
ValNo = interval.getNextValue(defIndex, CopyMI, VNInfoAllocator);
assert(ValNo->id == 0 && "First value in interval is not 0?");
@@ -435,9 +436,8 @@
assert(interval.containsOneValue());
unsigned DefIndex = getDefIndex(interval.getValNumInfo(0)->def);
unsigned RedefIndex = getDefIndex(MIIdx);
- // Earlyclobbers move back one.
- if (MO.isEarlyClobber())
- RedefIndex = getUseIndex(MIIdx);
+ // It cannot be an early clobber MO.
+ assert(!MO.isEarlyClobber() && "Unexpected early clobber!");
const LiveRange *OldLR = interval.getLiveRangeContaining(RedefIndex-1);
VNInfo *OldValNo = OldLR->valno;
@@ -505,9 +505,8 @@
// live until the end of the block. We've already taken care of the
// rest of the live range.
unsigned defIndex = getDefIndex(MIIdx);
- // Earlyclobbers move back one.
- if (MO.isEarlyClobber())
- defIndex = getUseIndex(MIIdx);
+ // It cannot be an early clobber MO.
+ assert(!MO.isEarlyClobber() && "Unexpected early clobber!");
VNInfo *ValNo;
MachineInstr *CopyMI = NULL;
@@ -592,8 +591,11 @@
// Already exists? Extend old live interval.
LiveInterval::iterator OldLR = interval.FindLiveRangeContaining(start);
- VNInfo *ValNo = (OldLR != interval.end())
+ bool Extend = OldLR != interval.end();
+ VNInfo *ValNo = Extend
? OldLR->valno : interval.getNextValue(start, CopyMI, VNInfoAllocator);
+ if (MO.isEarlyClobber() && Extend)
+ ValNo->redefByEC = true;
LiveRange LR(start, end, ValNo);
interval.addRange(LR);
interval.addKill(LR.valno, end);