search for: undef

Hi, > Both A and B are undef: > LHS = (undef & undef) | (undef & undef) = undef // Since ~undef = undef > RHS = undef > Thus transform is correct. LLVM documentation (http://llvm.org/docs/LangRef.html#undefined-values) suggests that it is unsafe to consider (a & undef = undef) and (a | und...

...IN__ 2.2250738585072014e-308 #define __PTRDIFF_TYPE__ int #define __LDBL_MIN_10_EXP__ (-4931) #define __REGISTER_PREFIX__ #define __LDBL_DIG__ 18 #define __NO_INLINE__ 1 #define __i386 1 #define __FLT_MANT_DIG__ 24 #define __VERSION__ "3.3.3 (SuSE Linux)" config.h: #define _CONFIG_H /* #undef SETEUID_BREAKS_SETUID */ /* #undef BROKEN_SETREUID */ /* #undef BROKEN_SETREGID */ /* #undef BROKEN_SETRESUID */ /* #undef BROKEN_SETRESGID */ #define SPT_TYPE SPT_REUSEARGV /* #undef SPT_PADCHAR */ /* #undef BROKEN_SYS_TERMIO_H */ /* #undef HAVE_SECUREWARE */ #define LOGIN_PROGRAM_FALLBACK "/...

Thanks for your answers. Another example of unsound transformation on Boolean algebra. According to the LLVM documentation (http://llvm.org/docs/LangRef.html#undefined-values) it is unsafe to consider ' a & undef = undef ' and ' a | undef = undef ' but 'undef xor undef = undef' is safe. Now, given an expression ((a & (~b)) | ((~a) & b)) where a and b are undef expressions, the value must be specialized to some constant (e....

Hi Duncan, Thank you for your comment to the bug 16257. I am new to LLVM, so not all the aspects of LLVM's /"undef"/ seem clear to me yet. I read and understood the examples from the LLVM documentation: http://llvm.org/docs/LangRef.html#undefined-values However, those examples do not cover all of the possible contexts where /"undef"/ can appear. E.g., I can't realize why /"fmul undef,...

Hi Duncan, Thank you a lot for your time to provide that great and informative explanation. Now the "undef" logic makes much more sense for me. >> /You are wrong to say that "div undef, %X" is folded to "undef" by InstructionSimplify, it is folded to zero./ My mistake. I meant to say "*f****div* undef, %X" is folded to "undef" (not integer "div...

Duncan, > Hi Oleg, > >> >> /This is either a mistake, or a decision that in LLVM IR snans >> are always >> considered to be signalling. / >> Yes, this seems to be an agreement to treat "undef" as a SNaN for >> "fdiv". > > "undef" is whatever bit pattern you want it to be, i.e. the compiler > can assume it is any convenient value. For one fdiv optimization > maybe it is convenient to choose it to be the bit pattern of an snan, > for some...

...On Thu, Dec 12, 2013 at 5:43 PM, Owen Anderson <resistor at mac.com > <mailto:resistor at mac.com>> wrote: > > > On Dec 12, 2013, at 4:57 PM, Philip Reames > <listmail at philipreames.com <mailto:listmail at philipreames.com>> wrote: > >> undef + any == NaN (since undef can be NaN) or undef + any (since >> undef could be zero) > > undef + non-NaN is still undef. The compiler is free to choose any > value of the type it wishes when simplifying an undef expression. > The important point is that it still...

I don't know of a way to do it from the command-line, but if you're willing to change the IR, you can add the optsize (for -Os) or minsize (for -Oz) IR attribute to the function you're compiling. On Fri, Sep 2, 2016 at 5:59 AM, Bruce Hoult via llvm-dev < llvm-dev at lists.llvm.org> wrote: > Idle question, if anyone is reading still ... how do you get llc to do -Os > or

Hi, This is a follow up on a discussion around shufflevector with undef mask in https://reviews.llvm.org/D70641 and https://bugs.llvm.org/show_bug.cgi?id=43958. The current semantics of shufflevector in http://llvm.org/docs/LangRef.html#shufflevector-instruction states: "If the shuffle mask is undef, the result vector is undef. If any element of the mask oper...

On Dec 12, 2013, at 4:57 PM, Philip Reames <listmail at philipreames.com> wrote: > undef + any == NaN (since undef can be NaN) or undef + any (since undef could be zero) undef + non-NaN is still undef. The compiler is free to choose any value of the type it wishes when simplifying an undef expression. The important point is that it still has to be a value of that type. Hence, predi...

...leg, > > On 17/09/14 18:45, Oleg Ranevskyy wrote: >> Hi, >> >> Thank you for all your helpful comments. >> >> To sum up, below is the list of correct folding examples for fadd: >> (1) fadd %x, -0.0 -> %x >> (2) fadd undef, undef -> undef >> (3) fadd %x, undef -> NaN (undef is a NaN which >> is propagated) >> >> Looking through the code I found the "NoNaNs" flag accessed through >> an instance >> of the FastMathFlags class. >> (2...

...Constant:i64<0>, Constant:i64<0>, Constant:i64<0>, Constant:i64<0>, Constant:i64<0>, Constant:i64<0>, Constant:i64<0>, Constant:i64<0>, Constant:i64<0>, Constant:i64<0>, Constant:i... Split node result: t123: v64i64 = BUILD_VECTOR undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:i64, undef:... Split node result: t124: v32i64 = BUILD_VECTOR undef:i64, undef:i64, undef:i64...

Hi, At line 2292, lib/VMCore/ConstantFold.cpp (llvm2.7 release) Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1, Constant *C2) { ... // Handle UndefValue up front. if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { switch (Opcode) { case Instruction::Xor: if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // Handle undef ^ undef -> 0 special case. This is a common // idiom (misuse)....

...ld x86_64-unknown-linux-gnu --host arm-linux-gnueabihf --disable-assertions --disable-check-asm --enable-intrinsics CFLAGS=-O3 --disable-shared When configuring with floating-point and intrinsics enabled as above, the generated config.h only has OPUS_ARM_MAY_HAVE_NEON_INTR defined (to 1), with /* #undef OPUS_ARM_ASM */ /* #undef OPUS_ARM_INLINE_ASM */ /* #undef OPUS_ARM_INLINE_EDSP */ /* #undef OPUS_ARM_INLINE_MEDIA */ /* #undef OPUS_ARM_INLINE_NEON */ /* #undef OPUS_ARM_MAY_HAVE_EDSP */ /* #undef OPUS_ARM_MAY_HAVE_MEDIA */ /* #undef OPUS_ARM_MAY_HAVE_NEON */ /* #undef OPUS_ARM_PRESUME_AARCH64_NEO...

On Thu, Dec 12, 2013 at 5:43 PM, Owen Anderson <resistor at mac.com> wrote: > > On Dec 12, 2013, at 4:57 PM, Philip Reames <listmail at philipreames.com> > wrote: > > undef + any == NaN (since undef can be NaN) or undef + any (since undef > could be zero) > > > undef + non-NaN is still undef. The compiler is free to choose any value > of the type it wishes when simplifying an undef expression. The important > point is that it still has to be a valu...

Hello, I'd like to offer an alternative solution to the "poison problem": remove it. What follows is rather informal. I'd happily write up a nicer document if this RFC stands up to scrutiny. The idea was born from two observations: - undef was introduced to model a load of uninitialized memory, a form of undefined behavior. - poison was introduced to model integer overflow, another form of undefined behavior. I find it awkward that one form of uninitialized behavior is more or less powerful than another. We rely on the following pr...

...5:43 PM, Owen Anderson <resistor at mac.com >> <mailto:resistor at mac.com>> wrote: >> >> >> On Dec 12, 2013, at 4:57 PM, Philip Reames >> <listmail at philipreames.com <mailto:listmail at philipreames.com>> wrote: >> >> undef + any == NaN (since undef can be NaN) or undef + any (since >>> undef could be zero) >>> >> >> undef + non-NaN is still undef. The compiler is free to choose any >> value of the type it wishes when simplifying an undef expression. >> The...

Hi, Thank you for all your helpful comments. To sum up, below is the list of correct folding examples for fadd: (1) fadd %x, -0.0 -> %x (2) fadd undef, undef -> undef (3) fadd %x, undef -> NaN (undef is a NaN which is propagated) Looking through the code I found the "NoNaNs" flag accessed through an instance of the FastMathFlags class. (2) and (3) should probably depend on it. If the flag is set, (2...

Ok, makes sense. My suggestion is that we patch the IR Verifier to ensure that the mask is indeed a vector of constants and/or undefs. Right now it only runs the standard checks for instructions. We will also run Alive2 on the test suite to make sure undef is never replaced in practice. Thanks, Nuno -----Original Message----- From: Eli Friedman <efriedma at quicinc.com> Sent: 27 de novembro de 2019 01:10 To: Nuno Lopes...

Hi all, I have been trying to understand the use of undef in both sequential and concurrent programs. >From the LLVM Language Reference Manual, I see the following definition of undef. "Undef can be used anywhere a constant is expected, and indicates that the user of the value may receive an unspecified bit-pattern". LLVM Language Reference...