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Avoid commuting a def MI in order to coalesce a copy instruction away if any use of the same val# is a copy instruction that has already been coalesced.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48833 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2008-03-26 19:03:01 +00:00
parent e326332acd
commit ed70cbb3f3
3 changed files with 62 additions and 2 deletions
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14
lib/CodeGen/SimpleRegisterCoalescing.cpp
View File

@ -283,6 +283,17 @@ bool SimpleRegisterCoalescing::RemoveCopyByCommutingDef(LiveInterval &IntA,
if (HasOtherReachingDefs(IntA, IntB, AValNo, BValNo))
return false;
// If some of the uses of IntA.reg is already coalesced away, return false.
// It's not possible to determine whether it's safe to perform the coalescing.
for (MachineRegisterInfo::use_iterator UI = mri_->use_begin(IntA.reg),
UE = mri_->use_end(); UI != UE; ++UI) {
MachineInstr *UseMI = &*UI;
unsigned UseIdx = li_->getInstructionIndex(UseMI);
LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx);
if (ULR->valno == AValNo && JoinedCopies.count(UseMI))
return false;
}
// At this point we have decided that it is legal to do this
// transformation. Start by commuting the instruction.
MachineBasicBlock *MBB = DefMI->getParent();
@ -323,8 +334,7 @@ bool SimpleRegisterCoalescing::RemoveCopyByCommutingDef(LiveInterval &IntA,
MachineInstr *UseMI = &*UI;
++UI;
if (JoinedCopies.count(UseMI))
// It'll no longer be "joined" after the change.
JoinedCopies.erase(UseMI);
continue;
unsigned UseIdx = li_->getInstructionIndex(UseMI);
LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx);
if (ULR->valno != AValNo)

1
lib/CodeGen/VirtRegMap.cpp
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@ -1593,6 +1593,7 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM) {
}
}
assert(PhysReg && "VR not assigned a physical register?");
RegInfo->setPhysRegUsed(PhysReg);
unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg;
ReusedOperands.markClobbered(RReg);

49
test/CodeGen/X86/2007-03-26-CoalescerBug.ll Normal file
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@ -0,0 +1,49 @@
; RUN: llvm-as < %s | llc -march=x86
@data = external global [339 x i64]
define void @foo(...) {
bb1:
%t43 = load i64* getelementptr ([339 x i64]* @data, i32 0, i64 212), align 4
br i1 false, label %bb80, label %bb6
bb6:
br i1 false, label %bb38, label %bb265
bb265:
ret void
bb38:
br i1 false, label %bb80, label %bb49
bb80:
br i1 false, label %bb146, label %bb268
bb49:
ret void
bb113:
ret void
bb268:
%t1062 = shl i64 %t43, 3
%t1066 = shl i64 0, 3
br label %bb85
bb85:
%t1025 = phi i64 [ 0, %bb268 ], [ %t102.0, %bb234 ]
%t1028 = phi i64 [ 0, %bb268 ], [ %t1066, %bb234 ]
%t1031 = phi i64 [ 0, %bb268 ], [ %t103.0, %bb234 ]
%t1034 = phi i64 [ 0, %bb268 ], [ %t1066, %bb234 ]
%t102.0 = add i64 %t1028, %t1025
%t103.0 = add i64 %t1034, %t1031
br label %bb86
bb86:
%t108.0 = phi i64 [ %t102.0, %bb85 ], [ %t1139, %bb248 ]
%t110.0 = phi i64 [ %t103.0, %bb85 ], [ %t1142, %bb248 ]
br label %bb193
bb193:
%t1081 = add i64 %t110.0, -8
%t1087 = add i64 %t108.0, -8
br i1 false, label %bb193, label %bb248
bb248:
%t1139 = add i64 %t108.0, %t1062
%t1142 = add i64 %t110.0, %t1062
br i1 false, label %bb86, label %bb234
bb234:
br i1 false, label %bb85, label %bb113
bb146:
ret void
}