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[PowerPC] Use helper functions to check sign-/zero-extended value

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Helper functions to identify sign- and zero-extending machine instruction is introduced in rL315888.
This patch makes PPCInstrInfo::optimizeCompareInstr use the helper functions. It simplifies the code and also makes possible more optimizations since the helper can do more analysis than the original check code; I observed about 5000 more compare instructions are eliminated while building LLVM.

Also, this patch fixes a bug in helpers on ANDIo instruction handling due to the order of checks. This bug causes a failure in an existing test case for optimizeCompareInstr.

Differential Revision: https://reviews.llvm.org/D38988

llvm-svn: 316071
This commit is contained in:
Hiroshi Inoue 2017-10-18 10:31:19 +00:00
parent d687162dad
commit abf01efc5a
2 changed files with 32 additions and 23 deletions
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34
lib/Target/PowerPC/PPCInstrInfo.cpp
View File

@ -1634,37 +1634,20 @@ bool PPCInstrInfo::optimizeCompareInstr(MachineInstr &CmpInstr, unsigned SrcReg,
// Get the unique definition of SrcReg.
MachineInstr *MI = MRI->getUniqueVRegDef(SrcReg);
if (!MI) return false;
int MIOpC = MI->getOpcode();
bool equalityOnly = false;
bool noSub = false;
if (isPPC64) {
if (is32BitSignedCompare) {
// We can perform this optimization only if MI is sign-extending.
if (MIOpC == PPC::SRAW || MIOpC == PPC::SRAWo ||
MIOpC == PPC::SRAWI || MIOpC == PPC::SRAWIo ||
MIOpC == PPC::EXTSB || MIOpC == PPC::EXTSBo ||
MIOpC == PPC::EXTSH || MIOpC == PPC::EXTSHo ||
MIOpC == PPC::EXTSW || MIOpC == PPC::EXTSWo) {
if (isSignExtended(*MI))
noSub = true;
} else
else
return false;
} else if (is32BitUnsignedCompare) {
// 32-bit rotate and mask instructions are zero extending only if MB <= ME
bool isZeroExtendingRotate =
(MIOpC == PPC::RLWINM || MIOpC == PPC::RLWINMo ||
MIOpC == PPC::RLWNM || MIOpC == PPC::RLWNMo)
&& MI->getOperand(3).getImm() <= MI->getOperand(4).getImm();
// We can perform this optimization, equality only, if MI is
// zero-extending.
// FIXME: Other possible target instructions include ANDISo and
// RLWINM aliases, such as ROTRWI, EXTLWI, SLWI and SRWI.
if (MIOpC == PPC::CNTLZW || MIOpC == PPC::CNTLZWo ||
MIOpC == PPC::SLW || MIOpC == PPC::SLWo ||
MIOpC == PPC::SRW || MIOpC == PPC::SRWo ||
MIOpC == PPC::ANDIo ||
isZeroExtendingRotate) {
if (isZeroExtended(*MI)) {
noSub = true;
equalityOnly = true;
} else
@ -1811,7 +1794,7 @@ bool PPCInstrInfo::optimizeCompareInstr(MachineInstr &CmpInstr, unsigned SrcReg,
if (!MI) MI = Sub;
int NewOpC = -1;
MIOpC = MI->getOpcode();
int MIOpC = MI->getOpcode();
if (MIOpC == PPC::ANDIo || MIOpC == PPC::ANDIo8)
NewOpC = MIOpC;
else {
@ -2223,6 +2206,12 @@ PPCInstrInfo::isSignOrZeroExtended(const MachineInstr &MI, bool SignExt,
const MachineFunction *MF = MI.getParent()->getParent();
const MachineRegisterInfo *MRI = &MF->getRegInfo();
// If we know this instruction returns sign- or zero-extended result,
// return true.
if (SignExt ? isSignExtendingOp(MI):
isZeroExtendingOp(MI))
return true;
switch (MI.getOpcode()) {
case PPC::COPY: {
unsigned SrcReg = MI.getOperand(1).getReg();
@ -2339,8 +2328,7 @@ PPCInstrInfo::isSignOrZeroExtended(const MachineInstr &MI, bool SignExt,
}
default:
return SignExt?isSignExtendingOp(MI):
isZeroExtendingOp(MI);
break;
}
return false;
}

21
test/CodeGen/PowerPC/opt-cmp-inst-cr0-live.ll
View File

@ -78,3 +78,24 @@ if.end:
}
declare void @exit(i32 signext)
; Since %v1 and %v2 are zero-extended 32-bit values, %1 is also zero-extended.
; In this case, we want to use ORo instead of OR + CMPLWI.
; CHECK-LABEL: fn5
define zeroext i32 @fn5(i32* %p1, i32* %p2) {
; CHECK: ORo
; CHECK-NOT: CMP
; CHECK: BCC
%v1 = load i32, i32* %p1
%v2 = load i32, i32* %p2
%1 = or i32 %v1, %v2
%2 = icmp eq i32 %1, 0
br i1 %2, label %foo, label %bar
foo:
ret i32 1
bar:
ret i32 0
}