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If all sources of a PHI node are defined by an implicit_def, just emit an implicit_def instead of a copy.

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llvm-svn: 50927
This commit is contained in:
Evan Cheng 2008-05-10 00:17:50 +00:00
parent 89c91f81ae
commit cf4d5567d5
2 changed files with 36 additions and 7 deletions
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16
lib/CodeGen/PHIElimination.cpp
View File

@ -127,11 +127,15 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
return true;
}
static bool isSourceDefinedByImplicitDef(MachineInstr *MPhi, unsigned SrcIdx,
static bool isSourceDefinedByImplicitDef(MachineInstr *MPhi,
MachineRegisterInfo *MRI) {
unsigned SrcReg = MPhi->getOperand(SrcIdx*2+1).getReg();
for (unsigned i = 1; i != MPhi->getNumOperands(); i += 2) {
unsigned SrcReg = MPhi->getOperand(i).getReg();
MachineInstr *DefMI = MRI->getVRegDef(SrcReg);
return DefMI->getOpcode() == TargetInstrInfo::IMPLICIT_DEF;
if (!DefMI || DefMI->getOpcode() != TargetInstrInfo::IMPLICIT_DEF)
return false;
}
return true;
}
/// LowerAtomicPHINode - Lower the PHI node at the top of the specified block,
@ -156,9 +160,9 @@ void PNE::LowerAtomicPHINode(MachineBasicBlock &MBB,
// into the phi node destination.
//
const TargetInstrInfo *TII = MF.getTarget().getInstrInfo();
if (NumSrcs == 1 && isSourceDefinedByImplicitDef(MPhi, 0, MRI))
// If the only source of a PHI node is an implicit_def, just emit an
// implicit_def instead of a copy.
if (isSourceDefinedByImplicitDef(MPhi, MRI))
// If all sources of a PHI node are implicit_def, just emit an implicit_def
// instead of a copy.
BuildMI(MBB, AfterPHIsIt, TII->get(TargetInstrInfo::IMPLICIT_DEF), DestReg);
else
TII->copyRegToReg(MBB, AfterPHIsIt, DestReg, IncomingReg, RC, RC);

25
test/CodeGen/X86/2008-05-09-PHIElimBug.ll Normal file
View File

@ -0,0 +1,25 @@
; RUN: llvm-as < %s | llc -march=x86
%struct.V = type { <4 x float>, <4 x float>, <4 x float>, <4 x float>, <4 x float>, <4 x float>, <4 x float>, <4 x i32>, float*, float*, float*, float*, float, float, float, float, float, float, float, float, float, float, float, float, float, float, float, float, float, float, float, float, float, float, float, float, i32, i32, i32, i32, i32, i32, i32, i32 }
define fastcc void @t() nounwind {
entry:
br i1 false, label %bb23816.preheader, label %bb23821
bb23816.preheader: ; preds = %entry
%tmp23735 = and i32 0, 2 ; <i32> [#uses=0]
br label %bb23830
bb23821: ; preds = %entry
br i1 false, label %bb23830, label %bb23827
bb23827: ; preds = %bb23821
%tmp23829 = getelementptr %struct.V* null, i32 0, i32 42 ; <i32*> [#uses=0]
br label %bb23830
bb23830: ; preds = %bb23827, %bb23821, %bb23816.preheader
%scaledInDst.2.reg2mem.5 = phi i8 [ undef, %bb23827 ], [ undef, %bb23821 ], [ undef, %bb23816.preheader ] ; <i8> [#uses=1]
%toBool35047 = icmp eq i8 %scaledInDst.2.reg2mem.5, 0 ; <i1> [#uses=1]
%bothcond39107 = or i1 %toBool35047, false ; <i1> [#uses=0]
unreachable
}