[llvm-commits] [llvm] r48491 - in /llvm/trunk: lib/CodeGen/SelectionDAG/DAGCombiner.cpp test/CodeGen/X86/field-extract-use-trunc.ll
Christopher Lamb
christopher.lamb at gmail.com
Wed Mar 19 10:01:24 PDT 2008
There are two versions of isTruncateFree, one that takes Types, and
one that takes ValueTypes. Should i1 truncates be free in the Type
version but not so in the ValueType version?
--
Chris
On Mar 19, 2008, at 1:46 AM, Evan Cheng wrote:
> Well... Actually it should return true. MVT::i1 is promoted to
> MVT::i8 so on x86 it really should be free.
>
> Evan
>
> On Mar 19, 2008, at 1:28 AM, Christopher Lamb wrote:
>
>> Well, I'm not seeing that pessimization anymore. strange.
>>
>> On Mar 19, 2008, at 1:17 AM, Christopher Lamb wrote:
>>
>>> Fixing isTruncateFree for MVT::i1 seems to reduce code quality,
>>> it causes some extra mov's to pop up in the dg tests. =(
>>>
>>> On Mar 19, 2008, at 1:01 AM, Evan Cheng wrote:
>>>
>>>> No, it's not. Please fix. But that's a profitability issue, it
>>>> shouldn't cause miscompilation?
>>>>
>>>> Evan
>>>>
>>>> On Mar 19, 2008, at 12:54 AM, Christopher Lamb wrote:
>>>>
>>>>> X86 TargetLowering claims that truncate from any integer type
>>>>> to MVT::i1 is free. Is this correct?
>>>>>
>>>>> --
>>>>> Chris
>>>>>
>>>>> On Mar 18, 2008, at 3:23 PM, Bill Wendling wrote:
>>>>>
>>>>>> Hi Christopher,
>>>>>>
>>>>>> The attached testcase fails with this patch. I'm reverting it
>>>>>> temporarily.
>>>>>>
>>>>>> -bw
>>>>>>
>>>>>> On Tue, Mar 18, 2008 at 9:46 AM, Christopher Lamb
>>>>>> <christopher.lamb at gmail.com> wrote:
>>>>>>> Author: clamb
>>>>>>> Date: Tue Mar 18 11:46:39 2008
>>>>>>> New Revision: 48491
>>>>>>>
>>>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=48491&view=rev
>>>>>>> Log:
>>>>>>> Target independent DAG transform to use truncate for field
>>>>>>> extraction + sign extend on targets where this is profitable.
>>>>>>> Passes nightly on x86-64.
>>>>>>>
>>>>>>> Added:
>>>>>>> llvm/trunk/test/CodeGen/X86/field-extract-use-trunc.ll
>>>>>>> Modified:
>>>>>>> llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>>>>>>>
>>>>>>> Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>>>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/
>>>>>>> CodeGen/SelectionDAG/DAGCombiner.cpp?
>>>>>>> rev=48491&r1=48490&r2=48491&view=diff
>>>>>>>
>>>>>>>
>>>>>>> ================================================================
>>>>>>> ==============
>>>>>>> --- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>>>>>>> (original)
>>>>>>> +++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Tue
>>>>>>> Mar 18 11:46:39 2008
>>>>>>> @@ -2374,6 +2374,32 @@
>>>>>>> DAG.getValueType(EVT));
>>>>>>> }
>>>>>>>
>>>>>>> + // fold sra (shl X, m), result_size - n
>>>>>>> + // -> (sign_extend (trunc (shl X, result_size - n - m))) for
>>>>>>> + // result_size - n != m. If truncate is free for the
>>>>>>> target sext(shl) is
>>>>>>> + // likely to result in better code.
>>>>>>> + if (N0.getOpcode() == ISD::SHL) {
>>>>>>> + // Get the two constanst of the shifts, CN0 = m, CN = n.
>>>>>>> + const ConstantSDNode *N01C = dyn_cast<ConstantSDNode>
>>>>>>> (N0.getOperand(1));
>>>>>>> + if (N01C && N1C) {
>>>>>>> + // Determine if the truncate type's bitsize would
>>>>>>> correspond to
>>>>>>> + // an integer type for this target.
>>>>>>> + unsigned VTValSize = MVT::getSizeInBits(VT);
>>>>>>> + MVT::ValueType TruncVT = MVT::getIntegerType
>>>>>>> (VTValSize - N1C->getValue());
>>>>>>> + unsigned ShiftAmt = N1C->getValue() - N01C->getValue();
>>>>>>> +
>>>>>>> + // If the shift wouldn't be a noop, the truncated
>>>>>>> type is an actual type,
>>>>>>> + // and the truncate is free, then proceed with the
>>>>>>> transform.
>>>>>>> + if (ShiftAmt != 0 &&
>>>>>>> + !MVT::isExtendedVT(TruncVT) && TLI.isTruncateFree
>>>>>>> (VT, TruncVT)) {
>>>>>>> + SDOperand Amt = DAG.getConstant(ShiftAmt,
>>>>>>> TLI.getShiftAmountTy());
>>>>>>> + SDOperand Shift = DAG.getNode(ISD::SRL, VT,
>>>>>>> N0.getOperand(0), Amt);
>>>>>>> + SDOperand Trunc = DAG.getNode(ISD::TRUNCATE,
>>>>>>> TruncVT, Shift);
>>>>>>> + return DAG.getNode(ISD::SIGN_EXTEND, N->getValueType
>>>>>>> (0), Trunc);
>>>>>>> + }
>>>>>>> + }
>>>>>>> + }
>>>>>>> +
>>>>>>> // fold (sra (sra x, c1), c2) -> (sra x, c1+c2)
>>>>>>> if (N1C && N0.getOpcode() == ISD::SRA) {
>>>>>>> if (ConstantSDNode *C1 = dyn_cast<ConstantSDNode>
>>>>>>> (N0.getOperand(1))) {
>>>>>>>
>>>>>>> Added: llvm/trunk/test/CodeGen/X86/field-extract-use-trunc.ll
>>>>>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
>>>>>>> CodeGen/X86/field-extract-use-trunc.ll?rev=48491&view=auto
>>>>>>>
>>>>>>>
>>>>>>> ================================================================
>>>>>>> ==============
>>>>>>> --- llvm/trunk/test/CodeGen/X86/field-extract-use-trunc.ll
>>>>>>> (added)
>>>>>>> +++ llvm/trunk/test/CodeGen/X86/field-extract-use-trunc.ll
>>>>>>> Tue Mar 18 11:46:39 2008
>>>>>>> @@ -0,0 +1,39 @@
>>>>>>> +; RUN: llvm-as < %s | llc -march=x86 | grep sar | count 1
>>>>>>> +; RUN: llvm-as < %s | llc -march=x86-64 | not grep sar
>>>>>>> +
>>>>>>> +define i32 @test(i32 %f12) {
>>>>>>> + %tmp7.25 = lshr i32 %f12, 16
>>>>>>> + %tmp7.26 = trunc i32 %tmp7.25 to i8
>>>>>>> + %tmp78.2 = sext i8 %tmp7.26 to i32
>>>>>>> + ret i32 %tmp78.2
>>>>>>> +}
>>>>>>> +
>>>>>>> +define i32 @test2(i32 %f12) {
>>>>>>> + %f11 = shl i32 %f12, 8
>>>>>>> + %tmp7.25 = ashr i32 %f11, 24
>>>>>>> + ret i32 %tmp7.25
>>>>>>> +}
>>>>>>> +
>>>>>>> +define i32 @test3(i32 %f12) {
>>>>>>> + %f11 = shl i32 %f12, 13
>>>>>>> + %tmp7.25 = ashr i32 %f11, 24
>>>>>>> + ret i32 %tmp7.25
>>>>>>> +}
>>>>>>> +
>>>>>>> +define i64 @test4(i64 %f12) {
>>>>>>> + %f11 = shl i64 %f12, 32
>>>>>>> + %tmp7.25 = ashr i64 %f11, 32
>>>>>>> + ret i64 %tmp7.25
>>>>>>> +}
>>>>>>> +
>>>>>>> +define i16 @test5(i16 %f12) {
>>>>>>> + %f11 = shl i16 %f12, 2
>>>>>>> + %tmp7.25 = ashr i16 %f11, 8
>>>>>>> + ret i16 %tmp7.25
>>>>>>> +}
>>>>>>> +
>>>>>>> +define i16 @test6(i16 %f12) {
>>>>>>> + %f11 = shl i16 %f12, 8
>>>>>>> + %tmp7.25 = ashr i16 %f11, 8
>>>>>>> + ret i16 %tmp7.25
>>>>>>> +}
>>>>>>> \ No newline at end of file
>>>>>>>
>>>>>>>
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>>>>>>>
>>>>>>> <bugpoint-reduced-simplified.bc>
>>>>>> _______________________________________________
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>>>>>
>>>>> --
>>>>> Christopher Lamb
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> llvm-commits mailing list
>>>>> llvm-commits at cs.uiuc.edu
>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>>>
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>>>
>>> --
>>> Christopher Lamb
>>>
>>>
>>>
>>
>> --
>> Christopher Lamb
>>
>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>
--
Christopher Lamb
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