[llvm] r181937 - X86: Remove redundant test instructions
David Majnemer
david.majnemer at gmail.com
Thu May 16 19:03:49 PDT 2013
We can but this would prevent us from removing a test instruction if a cmov
was choosing between an adc instruction and 0.
On Thu, May 16, 2013 at 6:03 PM, Manman Ren <mren at apple.com> wrote:
>
> Hi David,
>
> Can we return false earlier if the definition MI uses EFLAGS, inside the
> following loop?
>
> Thanks,
> Manman
>
> for (; RI != RE; ++RI) {
> MachineInstr *Instr = &*RI;
> // Check whether CmpInstr can be made redundant by the current
> instruction.
> if (!IsCmpZero &&
> isRedundantFlagInstr(CmpInstr, SrcReg, SrcReg2, CmpValue, Instr)) {
> Sub = Instr;
> break;
> }
>
> if (Instr->modifiesRegister(X86::EFLAGS, TRI) ||
> Instr->readsRegister(X86::EFLAGS, TRI)) {
> // This instruction modifies or uses EFLAGS.
>
> // MOV32r0 etc. are implemented with xor which clobbers condition
> code.
> // They are safe to move up, if the definition to EFLAGS is dead and
> // earlier instructions do not read or write EFLAGS.
> if (!Movr0Inst && (Instr->getOpcode() == X86::MOV8r0 ||
> Instr->getOpcode() == X86::MOV16r0 ||
> Instr->getOpcode() == X86::MOV32r0 ||
> Instr->getOpcode() == X86::MOV64r0) &&
> Instr->registerDefIsDead(X86::EFLAGS, TRI)) {
> --> check whether MI uses EFLAGS
> Movr0Inst = Instr;
> continue;
> }
>
> // We can't remove CmpInstr.
> return false;
> }
> }
>
> On May 16, 2013, at 5:17 PM, David Majnemer wrote:
>
> Attached is a patch to address PR16031.
>
> The peephole tries to reorder MOV32r0 instructions so that they are before
> the instruction that modifies EFLAGS.
> The problem is that the peephole does not consider the case where the
> instruction that modifies EFLAGS also depends on them.
>
> This patch walks backwards until it finds an instruction that has a def
> but no use and inserts right before it.
> If it cannot find such an instruction, it skips the optimization.
>
>
> On Thu, May 16, 2013 at 12:03 PM, Manman Ren <mren at apple.com> wrote:
>
>>
>> This is related to PR16031.
>>
>> Please take a look,
>> Thanks,
>> Manman
>>
>> On May 15, 2013, at 3:45 PM, Pete Cooper wrote:
>>
>> Hi David
>>
>> This test is breaking a buildbot. Could you please take a look?
>>
>>
>> http://lab.llvm.org:8013/builders/clang-x86_64-darwin11-nobootstrap-RAincremental/builds/1779
>>
>> Thanks,
>> Pete
>> On May 15, 2013, at 3:03 PM, David Majnemer <david.majnemer at gmail.com>
>> wrote:
>>
>> Author: majnemer
>> Date: Wed May 15 17:03:08 2013
>> New Revision: 181937
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=181937&view=rev
>> Log:
>> X86: Remove redundant test instructions
>>
>> Increase the number of instructions LLVM recognizes as setting the ZF
>> flag. This allows us to remove test instructions that redundantly
>> recalculate the flag.
>>
>> Added:
>> llvm/trunk/test/CodeGen/X86/peep-test-4.ll
>> Modified:
>> llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
>>
>> Modified: llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrInfo.cpp?rev=181937&r1=181936&r2=181937&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Target/X86/X86InstrInfo.cpp (original)
>> +++ llvm/trunk/lib/Target/X86/X86InstrInfo.cpp Wed May 15 17:03:08 2013
>> @@ -3200,8 +3200,37 @@ inline static bool isDefConvertible(Mach
>> case X86::OR8ri: case X86::OR64rr: case X86::OR32rr:
>> case X86::OR16rr: case X86::OR8rr: case X86::OR64rm:
>> case X86::OR32rm: case X86::OR16rm: case X86::OR8rm:
>> + case X86::NEG8r: case X86::NEG16r: case X86::NEG32r: case
>> X86::NEG64r:
>> + case X86::SAR8r1: case X86::SAR16r1: case X86::SAR32r1:case
>> X86::SAR64r1:
>> + case X86::SHR8r1: case X86::SHR16r1: case X86::SHR32r1:case
>> X86::SHR64r1:
>> + case X86::SHL8r1: case X86::SHL16r1: case X86::SHL32r1:case
>> X86::SHL64r1:
>> + case X86::ADC32ri: case X86::ADC32ri8:
>> + case X86::ADC32rr: case X86::ADC64ri32:
>> + case X86::ADC64ri8: case X86::ADC64rr:
>> + case X86::SBB32ri: case X86::SBB32ri8:
>> + case X86::SBB32rr: case X86::SBB64ri32:
>> + case X86::SBB64ri8: case X86::SBB64rr:
>> case X86::ANDN32rr: case X86::ANDN32rm:
>> case X86::ANDN64rr: case X86::ANDN64rm:
>> + case X86::BEXTR32rr: case X86::BEXTR64rr:
>> + case X86::BEXTR32rm: case X86::BEXTR64rm:
>> + case X86::BLSI32rr: case X86::BLSI32rm:
>> + case X86::BLSI64rr: case X86::BLSI64rm:
>> + case X86::BLSMSK32rr:case X86::BLSMSK32rm:
>> + case X86::BLSMSK64rr:case X86::BLSMSK64rm:
>> + case X86::BLSR32rr: case X86::BLSR32rm:
>> + case X86::BLSR64rr: case X86::BLSR64rm:
>> + case X86::BZHI32rr: case X86::BZHI32rm:
>> + case X86::BZHI64rr: case X86::BZHI64rm:
>> + case X86::LZCNT16rr: case X86::LZCNT16rm:
>> + case X86::LZCNT32rr: case X86::LZCNT32rm:
>> + case X86::LZCNT64rr: case X86::LZCNT64rm:
>> + case X86::POPCNT16rr:case X86::POPCNT16rm:
>> + case X86::POPCNT32rr:case X86::POPCNT32rm:
>> + case X86::POPCNT64rr:case X86::POPCNT64rm:
>> + case X86::TZCNT16rr: case X86::TZCNT16rm:
>> + case X86::TZCNT32rr: case X86::TZCNT32rm:
>> + case X86::TZCNT64rr: case X86::TZCNT64rm:
>> return true;
>> }
>> }
>> @@ -3427,13 +3456,16 @@ optimizeCompareInstr(MachineInstr *CmpIn
>> }
>>
>> // Make sure Sub instruction defines EFLAGS and mark the def live.
>> - unsigned LastOperand = Sub->getNumOperands() - 1;
>> - assert(Sub->getNumOperands() >= 2 &&
>> - Sub->getOperand(LastOperand).isReg() &&
>> - Sub->getOperand(LastOperand).getReg() == X86::EFLAGS &&
>> - "EFLAGS should be the last operand of SUB, ADD, OR, XOR, AND");
>> - Sub->getOperand(LastOperand).setIsDef(true);
>> - Sub->getOperand(LastOperand).setIsDead(false);
>> + unsigned i = 0, e = Sub->getNumOperands();
>> + for (; i != e; ++i) {
>> + MachineOperand &MO = Sub->getOperand(i);
>> + if (MO.isReg() && MO.isDef() && MO.getReg() == X86::EFLAGS) {
>> + MO.setIsDead(false);
>> + break;
>> + }
>> + }
>> + assert(i != e && "Unable to locate a def EFLAGS operand");
>> +
>> CmpInstr->eraseFromParent();
>>
>> // Modify the condition code of instructions in OpsToUpdate.
>>
>> Added: llvm/trunk/test/CodeGen/X86/peep-test-4.ll
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/peep-test-4.ll?rev=181937&view=auto
>>
>> ==============================================================================
>> --- llvm/trunk/test/CodeGen/X86/peep-test-4.ll (added)
>> +++ llvm/trunk/test/CodeGen/X86/peep-test-4.ll Wed May 15 17:03:08 2013
>> @@ -0,0 +1,154 @@
>> +; RUN: llc < %s -march=x86-64 -mattr=+bmi,+bmi2,+popcnt | FileCheck %s
>> +declare void @foo(i32)
>> +
>> +; CHECK: neg:
>> +; CHECK: negl %edi
>> +; CHECK-NEXT: je
>> +; CHECK: jmp foo
>> +; CHECK: ret
>> +define void @neg(i32 %x) nounwind {
>> + %sub = sub i32 0, %x
>> + %cmp = icmp eq i32 %sub, 0
>> + br i1 %cmp, label %return, label %bb
>> +
>> +bb:
>> + tail call void @foo(i32 %sub)
>> + br label %return
>> +
>> +return:
>> + ret void
>> +}
>> +
>> +; CHECK: sar:
>> +; CHECK: sarl %edi
>> +; CHECK-NEXT: je
>> +; CHECK: jmp foo
>> +; CHECK: ret
>> +define void @sar(i32 %x) nounwind {
>> + %ashr = ashr i32 %x, 1
>> + %cmp = icmp eq i32 %ashr, 0
>> + br i1 %cmp, label %return, label %bb
>> +
>> +bb:
>> + tail call void @foo(i32 %ashr)
>> + br label %return
>> +
>> +return:
>> + ret void
>> +}
>> +
>> +; CHECK: shr:
>> +; CHECK: shrl %edi
>> +; CHECK-NEXT: je
>> +; CHECK: jmp foo
>> +; CHECK: ret
>> +define void @shr(i32 %x) nounwind {
>> + %ashr = lshr i32 %x, 1
>> + %cmp = icmp eq i32 %ashr, 0
>> + br i1 %cmp, label %return, label %bb
>> +
>> +bb:
>> + tail call void @foo(i32 %ashr)
>> + br label %return
>> +
>> +return:
>> + ret void
>> +}
>> +
>> +; CHECK: shl:
>> +; CHECK: addl %edi, %edi
>> +; CHECK-NEXT: je
>> +; CHECK: jmp foo
>> +; CHECK: ret
>> +define void @shl(i32 %x) nounwind {
>> + %shl = shl i32 %x, 1
>> + %cmp = icmp eq i32 %shl, 0
>> + br i1 %cmp, label %return, label %bb
>> +
>> +bb:
>> + tail call void @foo(i32 %shl)
>> + br label %return
>> +
>> +return:
>> + ret void
>> +}
>> +
>> +; CHECK: adc:
>> +; CHECK: movabsq $-9223372036854775808, %rax
>> +; CHECK-NEXT: addq %rdi, %rax
>> +; CHECK-NEXT: adcq $0, %rsi
>> +; CHECK-NEXT: sete %al
>> +; CHECK-NEXT: ret
>> +define zeroext i1 @adc(i128 %x) nounwind {
>> + %add = add i128 %x, 9223372036854775808
>> + %cmp = icmp ult i128 %add, 18446744073709551616
>> + ret i1 %cmp
>> +}
>> +
>> +; CHECK: sbb:
>> +; CHECK: cmpq %rdx, %rdi
>> +; CHECK-NEXT: sbbq %rcx, %rsi
>> +; CHECK-NEXT: setns %al
>> +; CHECK-NEXT: ret
>> +define zeroext i1 @sbb(i128 %x, i128 %y) nounwind {
>> + %sub = sub i128 %x, %y
>> + %cmp = icmp sge i128 %sub, 0
>> + ret i1 %cmp
>> +}
>> +
>> +; CHECK: andn:
>> +; CHECK: andnl %esi, %edi, %edi
>> +; CHECK-NEXT: je
>> +; CHECK: jmp foo
>> +; CHECK: ret
>> +define void @andn(i32 %x, i32 %y) nounwind {
>> + %not = xor i32 %x, -1
>> + %andn = and i32 %y, %not
>> + %cmp = icmp eq i32 %andn, 0
>> + br i1 %cmp, label %return, label %bb
>> +
>> +bb:
>> + tail call void @foo(i32 %andn)
>> + br label %return
>> +
>> +return:
>> + ret void
>> +}
>> +
>> +; CHECK: bextr:
>> +; CHECK: bextrl %esi, %edi, %edi
>> +; CHECK-NEXT: je
>> +; CHECK: jmp foo
>> +; CHECK: ret
>> +declare i32 @llvm.x86.bmi.bextr.32(i32, i32) nounwind readnone
>> +define void @bextr(i32 %x, i32 %y) nounwind {
>> + %bextr = tail call i32 @llvm.x86.bmi.bextr.32(i32 %x, i32 %y)
>> + %cmp = icmp eq i32 %bextr, 0
>> + br i1 %cmp, label %return, label %bb
>> +
>> +bb:
>> + tail call void @foo(i32 %bextr)
>> + br label %return
>> +
>> +return:
>> + ret void
>> +}
>> +
>> +; CHECK: popcnt:
>> +; CHECK: popcntl
>> +; CHECK-NEXT: je
>> +; CHECK: jmp foo
>> +; CHECK: ret
>> +declare i32 @llvm.ctpop.i32(i32) nounwind readnone
>> +define void @popcnt(i32 %x) nounwind {
>> + %popcnt = tail call i32 @llvm.ctpop.i32(i32 %x)
>> + %cmp = icmp eq i32 %popcnt, 0
>> + br i1 %cmp, label %return, label %bb
>> +;
>> +bb:
>> + tail call void @foo(i32 %popcnt)
>> + br label %return
>> +;
>> +return:
>> + ret void
>> +}
>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>
>>
>>
> <pr16031.diff>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20130516/ff88ee6c/attachment.html>
More information about the llvm-commits
mailing list