[llvm-commits] [llvm] r166422 - in /llvm/trunk: include/llvm/Attributes.h lib/AsmParser/LLLexer.cpp lib/AsmParser/LLParser.cpp lib/AsmParser/LLToken.h lib/VMCore/Attributes.cpp
Evan Cheng
evan.cheng at apple.com
Mon Oct 22 22:24:09 PDT 2012
On Oct 22, 2012, at 12:56 PM, Chandler Carruth <chandlerc at google.com> wrote:
> On Mon, Oct 22, 2012 at 10:33 AM, Nadav Rotem <nrotem at apple.com> wrote:
>> Author: nadav
>> Date: Mon Oct 22 12:33:31 2012
>> New Revision: 166422
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=166422&view=rev
>> Log:
>> Add the "ForceSizeOpt" attribute.
>>
>> Patch by Quentin Colombet <qcolombet at apple.com>
>>
>> Original description:
>> """
>> The attached patch is the first step to have a better control on Oz related optimizations.
>> The Oz optimization level focuses on code size, thus I propose to add an attribute called ForceSizeOpt.
>> """
>
> So, Quentin, sorry I didn't see your original email, but I think
> ForceSizeOpt is the wrong name here.
>
> -Oz isn't about *forcing* the size-opt use case. It doesn't override
> anything, etc. It's about how we optimize for size.
>
> -Os --> When we could get performance at a significant cost to size,
> don't go after that performance. That said, don't actively degrade
> performance just to get size.
> -Oz --> Actively degrade performance to shrink the code.
>
> The important difference is that -Os should not really make code any
> slower than -O0 or even -O1. On the other hand -Oz might actively slow
> code down, and do other crazy things just to achieve a size reduction.
>
My read of -Os is optimize for speed is priority 1, code size 2. -Oz is code size 1, speed 2. I think saying -Oz would intentionally generate slower code for the sake of code size is going a bit too far. So I think the name kinda makes sense in this context. It's at least better than Chris' OptSizeHarder.
The right solution might be something like -Os[123] if anyone wants to start doing some really aggressive code size optimization.
Evan
> I would call this something more like "MinSizeOpt" or in prose
> "optimize and minimize size" as opposed to "SizeOpt" and "optimize
> without growing size".
>
>>
>>
>> Modified:
>> llvm/trunk/include/llvm/Attributes.h
>> llvm/trunk/lib/AsmParser/LLLexer.cpp
>> llvm/trunk/lib/AsmParser/LLParser.cpp
>> llvm/trunk/lib/AsmParser/LLToken.h
>> llvm/trunk/lib/VMCore/Attributes.cpp
>>
>> Modified: llvm/trunk/include/llvm/Attributes.h
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Attributes.h?rev=166422&r1=166421&r2=166422&view=diff
>> ==============================================================================
>> --- llvm/trunk/include/llvm/Attributes.h (original)
>> +++ llvm/trunk/include/llvm/Attributes.h Mon Oct 22 12:33:31 2012
>> @@ -84,7 +84,8 @@
>> StackProtectReq = 24, ///< Stack protection required.
>> StructRet = 25, ///< Hidden pointer to structure to return
>> UWTable = 26, ///< Function must be in a unwind table
>> - ZExt = 27 ///< Zero extended before/after call
>> + ZExt = 27, ///< Zero extended before/after call
>> + ForceSizeOpt = 28 ///< Function must be optimized for size first
>> };
>> private:
>> AttributesImpl *Attrs;
>> @@ -152,7 +153,8 @@
>> hasAttribute(Attributes::UWTable) ||
>> hasAttribute(Attributes::NonLazyBind) ||
>> hasAttribute(Attributes::ReturnsTwice) ||
>> - hasAttribute(Attributes::AddressSafety);
>> + hasAttribute(Attributes::AddressSafety) ||
>> + hasAttribute(Attributes::ForceSizeOpt);
>> }
>>
>> bool operator==(const Attributes &A) const {
>> @@ -263,7 +265,8 @@
>> .removeAttribute(Attributes::UWTable)
>> .removeAttribute(Attributes::NonLazyBind)
>> .removeAttribute(Attributes::ReturnsTwice)
>> - .removeAttribute(Attributes::AddressSafety);
>> + .removeAttribute(Attributes::AddressSafety)
>> + .removeAttribute(Attributes::ForceSizeOpt);
>> }
>>
>> uint64_t Raw() const { return Bits; }
>>
>> Modified: llvm/trunk/lib/AsmParser/LLLexer.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/AsmParser/LLLexer.cpp?rev=166422&r1=166421&r2=166422&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/AsmParser/LLLexer.cpp (original)
>> +++ llvm/trunk/lib/AsmParser/LLLexer.cpp Mon Oct 22 12:33:31 2012
>> @@ -557,6 +557,7 @@
>> KEYWORD(naked);
>> KEYWORD(nonlazybind);
>> KEYWORD(address_safety);
>> + KEYWORD(forcesizeopt);
>>
>> KEYWORD(type);
>> KEYWORD(opaque);
>>
>> Modified: llvm/trunk/lib/AsmParser/LLParser.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/AsmParser/LLParser.cpp?rev=166422&r1=166421&r2=166422&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/AsmParser/LLParser.cpp (original)
>> +++ llvm/trunk/lib/AsmParser/LLParser.cpp Mon Oct 22 12:33:31 2012
>> @@ -953,6 +953,7 @@
>> case lltok::kw_naked: B.addAttribute(Attributes::Naked); break;
>> case lltok::kw_nonlazybind: B.addAttribute(Attributes::NonLazyBind); break;
>> case lltok::kw_address_safety: B.addAttribute(Attributes::AddressSafety); break;
>> + case lltok::kw_forcesizeopt: B.addAttribute(Attributes::ForceSizeOpt); break;
>>
>> case lltok::kw_alignstack: {
>> unsigned Alignment;
>> @@ -1011,6 +1012,7 @@
>> case lltok::kw_nonlazybind:
>> case lltok::kw_returns_twice:
>> case lltok::kw_address_safety:
>> + case lltok::kw_forcesizeopt:
>> if (AttrKind != 2)
>> HaveError |= Error(AttrLoc, "invalid use of function-only attribute");
>> break;
>>
>> Modified: llvm/trunk/lib/AsmParser/LLToken.h
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/AsmParser/LLToken.h?rev=166422&r1=166421&r2=166422&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/AsmParser/LLToken.h (original)
>> +++ llvm/trunk/lib/AsmParser/LLToken.h Mon Oct 22 12:33:31 2012
>> @@ -109,6 +109,7 @@
>> kw_naked,
>> kw_nonlazybind,
>> kw_address_safety,
>> + kw_forcesizeopt,
>>
>> kw_type,
>> kw_opaque,
>>
>> Modified: llvm/trunk/lib/VMCore/Attributes.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/VMCore/Attributes.cpp?rev=166422&r1=166421&r2=166422&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/VMCore/Attributes.cpp (original)
>> +++ llvm/trunk/lib/VMCore/Attributes.cpp Mon Oct 22 12:33:31 2012
>> @@ -127,7 +127,7 @@
>> uint64_t EncodedAttrs = Attrs.Raw() & 0xffff;
>> if (Attrs.hasAttribute(Attributes::Alignment))
>> EncodedAttrs |= Attrs.getAlignment() << 16;
>> - EncodedAttrs |= (Attrs.Raw() & (0xfffULL << 21)) << 11;
>> + EncodedAttrs |= (Attrs.Raw() & (0xffffULL << 21)) << 11;
>> return EncodedAttrs;
>> }
>>
>> @@ -145,7 +145,7 @@
>> AttrBuilder B(EncodedAttrs & 0xffff);
>> if (Alignment)
>> B.addAlignmentAttr(Alignment);
>> - B.addRawValue((EncodedAttrs & (0xfffULL << 32)) >> 11);
>> + B.addRawValue((EncodedAttrs & (0xffffULL << 32)) >> 11);
>> return Attributes::get(C, B);
>> }
>>
>> @@ -201,6 +201,8 @@
>> Result += "nonlazybind ";
>> if (hasAttribute(Attributes::AddressSafety))
>> Result += "address_safety ";
>> + if (hasAttribute(Attributes::ForceSizeOpt))
>> + Result += "forcesizeopt ";
>> if (hasAttribute(Attributes::StackAlignment)) {
>> Result += "alignstack(";
>> Result += utostr(getStackAlignment());
>> @@ -324,6 +326,7 @@
>> case Attributes::UWTable: return 1 << 30;
>> case Attributes::NonLazyBind: return 1U << 31;
>> case Attributes::AddressSafety: return 1ULL << 32;
>> + case Attributes::ForceSizeOpt: return 1ULL << 33;
>> }
>> llvm_unreachable("Unsupported attribute type");
>> }
>>
>>
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