Re: basic asm and memory clobbers - Proposed solution

On Sun, Dec 20, 2015 at 02:53:15PM -0800, David Wohlferd wrote: > >You do not have to escape the { and } for extended asm, on this target, > >using %{ produces even an error. > > I believe the only the only target that needs to escape {} is i386, > since it's the only one that supports dialects

Re: basic asm and memory clobbers - Proposed solution

On 20.12.2015 23:53, David Wohlferd wrote: > On 12/20/2015 10:26 AM, Bernd Edlinger wrote: >> On 19.12.2015 19:54, David Wohlferd wrote: >> mep: mep_interrupt_saved_reg looks for ASM_INPUT in the body, and >> saves different registers if found. > I'm trying to follow this code. A real

Re: basic asm and memory clobbers - Proposed solution

On 12/20/2015 10:26 AM, Bernd Edlinger wrote: On 19.12.2015 19:54, David Wohlferd wrote: mep: mep_interrupt_saved_reg looks for ASM_INPUT in the body, and saves different registers if found. I'm trying to follow this code. A real challenge since I know nothing about mep. But what I see is:

Re: basic asm and memory clobbers - Proposed solution

Hi, On 19.12.2015 19:54, David Wohlferd wrote: > mep: mep_interrupt_saved_reg looks for ASM_INPUT in the body, and saves different registers if found. >>> I'm trying to follow this code. A real challenge since I know nothing >>> about mep. But what I see is: >>> >>> - This routine

Re: basic asm and memory clobbers - Proposed solution

On 12/18/2015 11:55 AM, Bernd Edlinger wrote: On 18.12.2015 10:27, David Wohlferd wrote: On 12/17/2015 11:30 AM, Bernd Edlinger wrote: Adding this warning to -Wall is too quickly and will bring the ia64, tilegx and mep ports into trouble. It doesn't look to me like adding the warnings will

Re: basic asm and memory clobbers - Proposed solution

On 12/17/2015 6:03 AM, Jeff Law wrote: On 12/17/2015 03:39 AM, Andrew Haley wrote: On 17/12/15 01:41, David Wohlferd wrote: On the contrary, I would be surprised to learn that there are ANY compilers (other than clang) that support gcc's extended asm format. Prepare to be surprised: Sun

Re: AW: basic asm and memory clobbers - Proposed solution

On 12/17/2015 11:30 AM, Bernd Edlinger wrote: On Thu, 17 Dec 2015 15:13:07, Bernd Schmidt wrote: What's your take on making -Wonly-top-basic-asm a default (either now or v7)? Is making it a non-default a waste of time because no one will ever see it? Or is making it a default too

Re: basic asm and memory clobbers - Proposed solution

On 18.12.2015 10:27, David Wohlferd wrote: > On 12/17/2015 11:30 AM, Bernd Edlinger wrote: >> On Thu, 17 Dec 2015 15:13:07, Bernd Schmidt wrote: What's your take on making -Wonly-top-basic-asm a default (either now or v7)? Is making it a non-default a waste of time because

Re: basic asm and memory clobbers - Proposed solution

On 17/12/15 01:41, David Wohlferd wrote: > On the contrary, I would be surprised to learn that there are ANY > compilers (other than clang) that support gcc's extended asm format. Prepare to be surprised: Sun Studio compilers seem to support it just fine. Andrew.

Re: basic asm and memory clobbers - Proposed solution

On 12/17/2015 02:41 AM, David Wohlferd wrote: So how about: - Update the basic asm docs to describe basic asm's current (and historical) semantics (ie clobber nothing). - Emphasize how that might be different from users' expectations or the behavior of other compilers. - Warn that this could

Re: basic asm and memory clobbers - Proposed solution

On 17/12/15 11:39, Andrew Haley wrote: > On 17/12/15 01:41, David Wohlferd wrote: >> On the contrary, I would be surprised to learn that there are ANY >> compilers (other than clang) that support gcc's extended asm format. > > Prepare to be surprised: Sun Studio compilers seem to support it >

Re: basic asm and memory clobbers - Proposed solution

On 12/17/2015 03:39 AM, Andrew Haley wrote: On 17/12/15 01:41, David Wohlferd wrote: On the contrary, I would be surprised to learn that there are ANY compilers (other than clang) that support gcc's extended asm format. Prepare to be surprised: Sun Studio compilers seem to support it just

AW: basic asm and memory clobbers - Proposed solution

Hi, On Thu, 17 Dec 2015 15:13:07, Bernd Schmidt wrote: > > What's your take on making -Wonly-top-basic-asm a default (either now or > > v7)? Is making it a non-default a waste of time because no one will > > ever see it? Or is making it a default too aggressive? What about > > adding

Re: basic asm and memory clobbers - Proposed solution

On 12/15/2015 2:43 PM, Joseph Myers wrote: On Tue, 15 Dec 2015, David Wohlferd wrote: Unlike top level, using basic asm within a function is deprecated. No new code should use this feature, but should use extended asm instead. Existing code should begin replacing such usage. Instances of

Re: basic asm and memory clobbers - Proposed solution

On 12/15/2015 5:01 PM, paul_kon...@dell.com wrote: On Dec 15, 2015, at 5:22 PM, David Wohlferd wrote: On 12/14/2015 1:53 AM, Andrew Haley wrote: This just seems like another argument for deprecating basic asm and pushing people to extended. Yes. I am not arguing

Re: basic asm and memory clobbers - Proposed solution

On 12/15/2015 12:42 PM, paul_kon...@dell.com wrote: In the codebase for the product I work on, I see about 200 of them. Many of those are the likes of asm("sync") for MIPS, which definitely wants to be treated as if it were asm ("sync" : : : "memory"). That's right, I meant to ask you about

Re: basic asm and memory clobbers - Proposed solution

On 12/15/2015 1:13 PM, Jeff Law wrote: Sadly, I'm putting most of this discussion into my gcc-7 queue anyway. Fair enough. If "clobbers" is what we're going to do, that sounds more like a phase 1 thing. That said, some people who have this problem may prefer to fix it sooner rather than

AW: basic asm and memory clobbers - Proposed solution

Hi, On 15. Dezember 2015 23:43, Joseph Myers wrote: > I think the typical use of basic asm is: you want to manipulate I/O > registers or other such state unknown to the compiler (not any registers > the compiler might use itself), and you want to do it in a way that is > maximally compatible with

Re: basic asm and memory clobbers - Proposed solution

On 12/14/2015 1:53 AM, Andrew Haley wrote: > This just seems like another argument for deprecating basic asm and pushing people to extended. Yes. I am not arguing against deprecation. We should do that. You know, there are several people who seem to generally support this direction. Not

Re: basic asm and memory clobbers - Proposed solution

On 12/15/2015 01:42 PM, paul_kon...@dell.com wrote: On Dec 15, 2015, at 7:52 AM, Bernd Schmidt wrote: On 12/14/2015 09:10 AM, Segher Boessenkool wrote: That, and adding a memory clobber degrades performance for a lot of existing basic asm that does not expect the

Re: basic asm and memory clobbers - Proposed solution

> On Dec 15, 2015, at 7:52 AM, Bernd Schmidt wrote: > > On 12/14/2015 09:10 AM, Segher Boessenkool wrote: >> That, and adding a memory clobber degrades performance for a lot of >> existing basic asm that does not expect the clobber, e.g. asm(""), >> asm("#"), asm("nop"),

Re: basic asm and memory clobbers - Proposed solution

On Tue, 15 Dec 2015, David Wohlferd wrote: > Unlike top level, using basic asm within a function is deprecated. No new code > should use this feature, but should use extended asm instead. Existing code > should begin replacing such usage. Instances of affected code can be found > using

Re: basic asm and memory clobbers - Proposed solution

> On Dec 15, 2015, at 5:22 PM, David Wohlferd wrote: > > On 12/14/2015 1:53 AM, Andrew Haley wrote: >> > This just seems like another argument for deprecating basic asm and >> > pushing people to extended. >> Yes. I am not arguing against deprecation. We should do

AW: basic asm and memory clobbers - Proposed solution

Hi, On 12/15/2015 13:52, Bernd Schmidt wrote: > > On 12/14/2015 09:10 AM, Segher Boessenkool wrote: > > That, and adding a memory clobber degrades performance for a lot of > > existing basic asm that does not expect the clobber, e.g. asm(""), > > asm("#"), asm("nop"), ... > > I wonder about

Re: basic asm and memory clobbers - Proposed solution

; resolved as 'Try it with extended.' > I'm just afraid that instead of pursuing any of these solutions, we > are going to pursue Solution #0: Do nothing. A rather unsatisfying > outcome after all this effort. You can't simultaenously insist that it gets fixed the way you want and

Re: basic asm and memory clobbers - Proposed solution

On Sun, Dec 13, 2015 at 10:59:11PM -0800, David Wohlferd wrote: > Is there a decision maker still teetering on the edge of making a call > here? I think people are waiting for consensus, and we won't get consensus until there is a good solution, something that gives workable semantics (whatever

Re: basic asm and memory clobbers - Proposed solution

incorrect code can be pointed at the text and >> told to fix their code. People whose code is damaged by optimizations >> can rewrite using extended to add dependencies (possibly doc this?). >> >> Solution 2: >> Change the docs to say that basic asm clobbers everything

Re: basic asm and memory clobbers - Proposed solution

Is there a decision maker still teetering on the edge of making a call here? Or have they all moved on and we are just talking among ourselves? I keep worrying that if I don't reply, someone will swoop in, read the last message in the thread, and charge off to make a changes based on that.

Re: basic asm and memory clobbers - Proposed solution

On 12/12/2015 1:51 AM, Andrew Haley wrote: Solution 2: Change the docs to say that basic asm clobbers everything (memory, all registers, etc) or perhaps just memory (some debate here), but that due to bugs that will eventually be addressed, it doesn't currently work this way. You've missed

Re: basic asm and memory clobbers - Proposed solution

e. People whose code is damaged by optimizations > can rewrite using extended to add dependencies (possibly doc this?). > > Solution 2: > Change the docs to say that basic asm clobbers everything (memory, all > registers, etc) or perhaps just memory (some debate here), but that

Re: basic asm and memory clobbers - Proposed solution

> On Dec 12, 2015, at 4:51 AM, Andrew Haley wrote: > > ... > You've missed the most practical solution, which meets most common > usage: clobber memory, but not registers. That allows most of the > effects that people intuitively want and expect, but avoids the > breakage of

Re: basic asm and memory clobbers - Proposed solution

amaged by optimizations can rewrite using extended to add dependencies (possibly doc this?). Solution 2: Change the docs to say that basic asm clobbers everything (memory, all registers, etc) or perhaps just memory (some debate here), but that due to bugs that will eventually be addressed, it

Re: basic asm and memory clobbers - Proposed solution

> On Dec 3, 2015, at 12:29 AM, Bernd Edlinger wrote: > >> ... >> If the goal is to order things wrt x, why wouldn't you just reference x? >> >> x = 1; >> asm volatile("nop":"+m"(x)); >> x = 0; >> > > Exactly, that is what I mean. Either the asm can use

Re: basic asm and memory clobbers - Proposed solution

Am 03.12.2015 um 16:24 schrieb paul_kon...@dell.com: > On the other hand, asm volatile ("foo":::) has a different meaning. > That specifically says that "foo" doesn't clobber anything. Well, not exactly, see the md_asm_adjust target callback. On i386, rs6000, visium, cris and mn10300

Re: basic asm and memory clobbers - Proposed solution

On 03.12.2015 00:27 David Wohlferd wrote: > On 12/2/2015 3:34 AM, Bernd Edlinger wrote: >> Hi, >> >>> Surely in code like that, you would make "x" volatile? Memory clobbers >>> are not a substitute for correct use of volatile accesses. >> No, >> >> It is as I wrote, a memory clobber is the only

Re: AW: basic asm and memory clobbers - Proposed solution

On 12/2/2015 3:34 AM, Bernd Edlinger wrote: Hi, Surely in code like that, you would make "x" volatile? Memory clobbers are not a substitute for correct use of volatile accesses. No, It is as I wrote, a memory clobber is the only way to guarantee that the asm statement is not move somewhere

Re: AW: basic asm and memory clobbers - Proposed solution

On 02/12/15 08:51, Bernd Edlinger wrote: > On 1.12.2015, David Wohlferd wrote: > On 12/1/2015 10:10 AM, Bernd Edlinger wrote: >>> But IMHO asm("bla":) isn't any better than asm("bla"). >>> I think _any_ asm with non-empty assembler string, that >>> claims to clobber _nothing_ is highly suspicious,

Re: AW: basic asm and memory clobbers - Proposed solution

Hi, > Surely in code like that, you would make "x" volatile? Memory clobbers > are not a substitute for correct use of volatile accesses. No, It is as I wrote, a memory clobber is the only way to guarantee that the asm statement is not move somewhere else. I changed the example to use

Re: AW: basic asm and memory clobbers - Proposed solution

On 02/12/15 12:34, Bernd Edlinger wrote: > Hi, > >> Surely in code like that, you would make "x" volatile? Memory clobbers >> are not a substitute for correct use of volatile accesses. > > No, > > It is as I wrote, a memory clobber is the only way to guarantee that > the asm statement is not

Re: basic asm and memory clobbers - Proposed solution

On 11/30/2015 4:01 AM, Andrew Haley wrote: >> There is a way for people to be clear about what they want to clobber, >> and that's to use extended asm. The way to clear up the ambiguity is to >> start deprecating basic asm, not to add to the confusion by changing its >> behavior after all

Re: basic asm and memory clobbers - Proposed solution

On 12/1/2015 10:10 AM, Bernd Edlinger wrote: > And a test case is missing too. > > I think this warning concentrates now only on basic asm. > And people will be probably fix it in the most easy way, > by just adding a colon. Probably true. At least I hope it's that easy for most people. > But

Re: basic asm and memory clobbers - Proposed solution

On 12/1/2015 8:08 AM, Richard Earnshaw wrote: > Formatting nit: the '== NULL_TREE)' should line up with the start of > 'lookup_attribute'. > Same here. Ok. Other than that, how do we proceed here? When pursuing a course to "deprecate and later completely remove basic asm within functions," I

Re: basic asm and memory clobbers - Proposed solution

On Tue, 1 Dec 2015, David Wohlferd wrote: > Saying it's dead in the docs is the first step to making it dead in the code. > This patch just implements an optional warning (unless #3,4 crank it up to a > default warning), but the intent is that eventually (v7? v8?) this turns into > a fatal error.

Re: basic asm and memory clobbers - Proposed solution

14g.zip >>> >>> Based on my understanding from the previous thread, this patch now >>> does what it needs to do (code-wise) to resolve this "basic asm and >>> memory clobbers" issue. As mentioned previously, this patch >>> introduces a n

AW: basic asm and memory clobbers - Proposed solution

On 1.12.2015, David Wohlferd wrote: On 12/1/2015 10:10 AM, Bernd Edlinger wrote: > > But IMHO asm("bla":) isn't any better than asm("bla"). > > I think _any_ asm with non-empty assembler string, that > > claims to clobber _nothing_ is highly suspicious, and worth to be > > warned about. I don't

Re: basic asm and memory clobbers - Proposed solution

On Tue, Dec 01, 2015 at 08:41:22PM -0700, Jeff Law wrote: > Isn't "asm" conditionally supported for ISO C++? In which case it's not > mandatory and semantics are implementation defined. Yes. > My strong preference is still to document the desired semantics for GCC > and treat anything that

Re: basic asm and memory clobbers - Proposed solution

On 12/1/2015 7:56 PM, Segher Boessenkool wrote: On Tue, Dec 01, 2015 at 08:41:22PM -0700, Jeff Law wrote: Isn't "asm" conditionally supported for ISO C++? In which case it's not mandatory and semantics are implementation defined. Yes. My strong preference is still to document the desired

Re: basic asm and memory clobbers - Proposed solution

On 12/01/2015 04:25 PM, Joseph Myers wrote: On Tue, 1 Dec 2015, David Wohlferd wrote: Saying it's dead in the docs is the first step to making it dead in the code. This patch just implements an optional warning (unless #3,4 crank it up to a default warning), but the intent is that eventually

Re: basic asm and memory clobbers - Proposed solution

On 12/01/2015 03:29 PM, David Wohlferd wrote: On 11/30/2015 4:01 AM, Andrew Haley wrote: >> There is a way for people to be clear about what they want to clobber, >> and that's to use extended asm. The way to clear up the ambiguity is to >> start deprecating basic asm, not to add to the

Re: basic asm and memory clobbers - Proposed solution

previous thread, this patch now >> does what it needs to do (code-wise) to resolve this "basic asm and >> memory clobbers" issue. As mentioned previously, this patch >> introduces a new warning (-Wonly-top-basic-asm), which is disabled by >> default. When enabled,

Re: basic asm and memory clobbers - Proposed solution

> On Nov 29, 2015, at 6:53 PM, David Wohlferd wrote: > > > > On 11/28/2015 10:30 AM, paul_kon...@dell.com wrote: >>> On Nov 28, 2015, at 2:02 AM, Bernd Edlinger >>> wrote: >>> >>> ... >>> Well, I start to think that Jeff is right, and we

Re: basic asm and memory clobbers - Proposed solution

On 11/29/2015 11:53 PM, David Wohlferd wrote: > > Trying to guess what people might have been expecting is a losing game. We have to do it all the time. > There is a way for people to be clear about what they want to clobber, > and that's to use extended asm. The way to clear up the

Re: basic asm and memory clobbers - Proposed solution

On 11/28/2015 10:30 AM, paul_kon...@dell.com wrote: On Nov 28, 2015, at 2:02 AM, Bernd Edlinger wrote: ... Well, I start to think that Jeff is right, and we should treat a asm ("") as if it were asm volatile ("" ::: ) but if the asm ("nonempty with optional %") we

RE: basic asm and memory clobbers - Proposed solution

--- gimple.c (Revision 230815) +++ gimple.c (Arbeitskopie) @@ -2567,6 +2567,10 @@ return true; } + /* Non-empty basic ASM implicitly clobbers memory. */ + if (gimple_asm_input_p (stmt)

Re: basic asm and memory clobbers - Proposed solution

> On Nov 28, 2015, at 2:02 AM, Bernd Edlinger wrote: > > ... > Well, I start to think that Jeff is right, and we should treat a asm ("") as > if it > were asm volatile ("" ::: ) but if the asm ("nonempty with optional %") we > should > treat it as asm volatile

Re: basic asm and memory clobbers

On Fri, Nov 20, 2015 at 04:29:50PM +0100, Richard Henderson wrote: > On 11/20/2015 04:20 PM, Segher Boessenkool wrote: > >Should asm("bla"); then be an extended asm with no input, no outputs, > >no (non-automatic) clobbers? That would be the most straightforward and > >logical semantics, but

Re: basic asm and memory clobbers

Hi Bernd, On Fri, Nov 27, 2015 at 09:26:40AM +, Bernd Edlinger wrote: > On Tue, 17 Nov 2015 14:31:29, Jeff Law wrote: > > The benefit is traditional asms do the expected thing. With no way to > > describe dataflow, the only rational behaviour for a traditional asm is > > that it has to be

Re: basic asm and memory clobbers - Proposed solution

this "basic asm and memory clobbers" issue. As mentioned previously, this patch introduces a new warning (-Wonly-top-basic-asm), which is disabled by default. When enabled, it triggers a warning for any basic asm inside a function, unless the function has the "naked" attr

AW: basic asm and memory clobbers - Proposed solution

Hi, I just found this in the docs: The compiler copies the assembler instructions in a basic @code{asm} verbatim to the assembly language output file, without processing dialects or any of the @samp{%} operators that are available with extended @code{asm}. This results in minor differences

AW: basic asm and memory clobbers - Proposed solution

Hi, I just found this in the docs: The compiler copies the assembler instructions in a basic @code{asm} verbatim to the assembly language output file, without processing dialects or any of the @samp{%} operators that are available with extended @code{asm}. This results in minor differences

Re: AW: basic asm and memory clobbers - Proposed solution

On 11/27/2015 11:02 PM, Bernd Edlinger wrote: Hi, I just found this in the docs: The compiler copies the assembler instructions in a basic @code{asm} verbatim to the assembly language output file, without processing dialects or any of the @samp{%} operators that are available with extended

Re: basic asm and memory clobbers

Hi, On Tue, 17 Nov 2015 14:31:29, Jeff Law wrote: > The benefit is traditional asms do the expected thing. With no way to > describe dataflow, the only rational behaviour for a traditional asm is that > it has to be considered a use/clobber of memory and hard registers. I'd like to mention

Re: basic asm and memory clobbers

On Fri, 20 Nov 2015, Richard Henderson wrote: > I'd be perfectly happy to deprecate and later completely remove basic asm > within functions. We've explictly promised (directed to kernel people IIRC) that the empty basic asm; 'asm ("")', has forward-compatible outlining magic, so people would not

Re: basic asm and memory clobbers

On Thu, Nov 26, 2015 at 05:30:48AM -0500, Hans-Peter Nilsson wrote: > On Fri, 20 Nov 2015, Richard Henderson wrote: > > I'd be perfectly happy to deprecate and later completely remove basic asm > > within functions. > > We've explictly promised (directed to kernel people IIRC) that > the empty

Re: basic asm and memory clobbers

On Thu, 26 Nov 2015, Segher Boessenkool wrote: > On Thu, Nov 26, 2015 at 05:30:48AM -0500, Hans-Peter Nilsson wrote: > > On Fri, 20 Nov 2015, Richard Henderson wrote: > > > I'd be perfectly happy to deprecate and later completely remove basic asm > > > within functions. > > > > We've explictly

Re: basic asm and memory clobbers

On 11/26/2015 8:26 AM, Hans-Peter Nilsson wrote: On Thu, 26 Nov 2015, Segher Boessenkool wrote: On Thu, Nov 26, 2015 at 05:30:48AM -0500, Hans-Peter Nilsson wrote: On Fri, 20 Nov 2015, Richard Henderson wrote: I'd be perfectly happy to deprecate and later completely remove basic asm within

Re: basic asm and memory clobbers

>> To be clear, wouldn't asm("":) have the same effect? > > That does not matter. It'd require source-code changes to > users' code. My suggestion was to allow the exception to the "basic asm in a function" warning, but change the docs to show using the new syntax. This does not require any

Re: basic asm and memory clobbers

On Thu, 26 Nov 2015, David Wohlferd wrote: > On 11/26/2015 8:26 AM, Hans-Peter Nilsson wrote: > > On Thu, 26 Nov 2015, Segher Boessenkool wrote: > > > On Thu, Nov 26, 2015 at 05:30:48AM -0500, Hans-Peter Nilsson wrote: > > > > @item noinline ... > > > > asm (""); ... > > I know, the point is that

Re: basic asm and memory clobbers

On 25/11/15 02:11, David Wohlferd wrote: > The 'fix' I am proposing is to give warnings for every use of basic asm > inside functions (top-level asm is not a problem). I'm not sure that's such a great idea on its own. My suggestion: 1. Clobber memory. 2. Document a rule which says that all

Re: basic asm and memory clobbers

On 11/24/2015 8:58 AM, paul_kon...@dell.com wrote: On Nov 23, 2015, at 8:39 PM, David Wohlferd wrote: On 11/23/2015 1:44 PM, paul_kon...@dell.com wrote: On Nov 23, 2015, at 4:36 PM, David Wohlferd wrote: ... The more I think about it, I'm

basic asm and memory clobbers - Proposed solution

I have solved the problem with my previous patch. Here's the update (feedback welcome): http://www.LimeGreenSocks.com/gcc/24414g.zip Based on my understanding from the previous thread, this patch now does what it needs to do (code-wise) to resolve this "basic asm and memory clobbers&q

Re: basic asm and memory clobbers

On Tue, Nov 24, 2015 at 8:58 AM, wrote: > > I'm really concerned with loosening the meaning of basic asm. I > wish I could find the documentation that says, or implies, that it > is a memory clobber. And/or that it is implicitly volatile. The volatile one is right there

Re: basic asm and memory clobbers

> On Nov 23, 2015, at 8:39 PM, David Wohlferd wrote: > > On 11/23/2015 1:44 PM, paul_kon...@dell.com wrote: >>> On Nov 23, 2015, at 4:36 PM, David Wohlferd wrote: >>> >>> ... The more I think about it, I'm just not keen on forcing all

Re: basic asm and memory clobbers

> On Nov 24, 2015, at 12:49 PM, Ian Lance Taylor wrote: > > On Tue, Nov 24, 2015 at 8:58 AM, wrote: >> >> I'm really concerned with loosening the meaning of basic asm. I >> wish I could find the documentation that says, or implies, that it >> is a

Re: basic asm and memory clobbers

On 23/11/15 21:02, David Wohlferd wrote: >> On 11/23/2015 2:04 AM, Andrew Haley wrote: >> > My warning still holds: there are modes of compilation on some >> > machines where you can't clobber all registers without causing reload >> > failures. This is why Jeff didn't fix this in 1999. So, if we

Re: basic asm and memory clobbers

On 11/23/2015 03:04 AM, Andrew Haley wrote: On 21/11/15 12:56, David Wohlferd wrote: So, what now? While I'd like to take the big step and start kicking out warnings for non-top-level right now, that may be too bold for phase 3. A more modest step for v6 would just provide a way to find them

Re: basic asm and memory clobbers

Note that basic asm is part of the standard C++ syntax. "An asm declaration has the form asm-definition: asm ( string-literal ) ; The asm declaration is conditionally-supported; its meaning is implementation-defined. [ Note: Typically it is used to pass information through the implementation to

Re: basic asm and memory clobbers

On 21/11/15 12:56, David Wohlferd wrote: > So, what now? > > While I'd like to take the big step and start kicking out warnings for > non-top-level right now, that may be too bold for phase 3. A more > modest step for v6 would just provide a way to find them (maybe > something like

Re: basic asm and memory clobbers

On 11/23/2015 07:22 PM, Segher Boessenkool wrote: Here is a test that shows that on at least PowerPC the basic asm is identical to the extended asm without clobber (compile with -O2 -S and -fno-ipa-icf if you want to have it easier to read). In this case, the basic asm is treated as not

Re: basic asm and memory clobbers

On Mon, Nov 23, 2015 at 09:48:42PM -0700, Jeff Law wrote: > On 11/23/2015 07:22 PM, Segher Boessenkool wrote: > > > >Here is a test that shows that on at least PowerPC the basic asm is > >identical to the extended asm without clobber (compile with -O2 -S and > >-fno-ipa-icf if you want to have it

Re: basic asm and memory clobbers

On 11/23/2015 10:12 PM, Segher Boessenkool wrote: On Mon, Nov 23, 2015 at 09:48:42PM -0700, Jeff Law wrote: On 11/23/2015 07:22 PM, Segher Boessenkool wrote: Here is a test that shows that on at least PowerPC the basic asm is identical to the extended asm without clobber (compile with -O2 -S

Re: basic asm and memory clobbers

On 11/23/2015 1:44 PM, paul_kon...@dell.com wrote: On Nov 23, 2015, at 4:36 PM, David Wohlferd wrote: ... The more I think about it, I'm just not keen on forcing all those old-style asms to change. If you mean you aren't keen to change them to "clobber all," I'm

Re: basic asm and memory clobbers

On Mon, Nov 23, 2015 at 05:39:17PM -0800, David Wohlferd wrote: > On 11/23/2015 1:44 PM, paul_kon...@dell.com wrote: > >>On Nov 23, 2015, at 4:36 PM, David Wohlferd wrote: > >> > >>... > >>>The more I think about it, I'm just not keen on forcing all those > >>>old-style

Re: basic asm and memory clobbers

On 11/23/2015 2:04 AM, Andrew Haley wrote: On 21/11/15 12:56, David Wohlferd wrote: So, what now? While I'd like to take the big step and start kicking out warnings for non-top-level right now, that may be too bold for phase 3. A more modest step for v6 would just provide a way to find them

Re: basic asm and memory clobbers

On 11/23/2015 12:37 PM, Jeff Law wrote: On 11/23/2015 03:04 AM, Andrew Haley wrote: On 21/11/15 12:56, David Wohlferd wrote: So, what now? While I'd like to take the big step and start kicking out warnings for non-top-level right now, that may be too bold for phase 3. A more modest step for

Re: basic asm and memory clobbers

> On Nov 23, 2015, at 4:36 PM, David Wohlferd wrote: > > ... >> The more I think about it, I'm just not keen on forcing all those old-style >> asms to change. > > If you mean you aren't keen to change them to "clobber all," I'm with you. > If you are worried about

Re: basic asm and memory clobbers

On 11/20/2015 3:55 PM, David Wohlferd wrote: On 11/20/2015 8:14 AM, Richard Henderson wrote: On 11/20/2015 04:34 PM, Jakub Jelinek wrote: Isn't that going to break too much code though? I mean, e.g. including libgcc... I don't know. My suspicion is very little. But that's actually what

Re: basic asm and memory clobbers

On 11/19/2015 5:53 PM, Sandra Loosemore wrote: On 11/19/2015 06:23 PM, David Wohlferd wrote: About the only immediate task would be to ensure that the documentation for traditional asms clearly documents the desired semantics and somehow note that there are known bugs in the implementation (ie

Re: basic asm and memory clobbers

On 20/11/15 01:23, David Wohlferd wrote: > I tried to picture the most basic case I can think of that uses > something clobber-able: > > for (int x=0; x < 1000; x++) >asm("#stuff"); > > This generates very simple and highly performant code: > > movl$1000, %eax > .L2: >

Re: basic asm and memory clobbers

On Fri, Nov 20, 2015 at 02:45:05AM -0800, David Wohlferd wrote: > On 11/19/2015 7:14 PM, Segher Boessenkool wrote: > >On Thu, Nov 19, 2015 at 05:23:55PM -0800, David Wohlferd wrote: > >>For that reason, I'd like to propose adding 2 new clobbers to extended > >>asm as part of this work: > >> >

Re: basic asm and memory clobbers

On 11/20/2015 3:14 AM, Andrew Haley wrote: On 20/11/15 10:37, David Wohlferd wrote: The intent for 24414 is to change basic asm such that it will become (quoting jeff) "an opaque blob that read/write/clobber any register or memory location." Such being the case, "memory" is not sufficient:

Re: basic asm and memory clobbers

On 20/11/15 10:37, David Wohlferd wrote: > The intent for 24414 is to change basic asm such that it will become > (quoting jeff) "an opaque blob that read/write/clobber any register or > memory location." Such being the case, "memory" is not sufficient: > > #define CLOBBERALL "eax", "ebx",

Re: basic asm and memory clobbers

On 11/19/2015 7:14 PM, Segher Boessenkool wrote: On Thu, Nov 19, 2015 at 05:23:55PM -0800, David Wohlferd wrote: For that reason, I'd like to propose adding 2 new clobbers to extended asm as part of this work: "clobberall" - This gives extended the same semantics as whatever the new basic asm

Re: basic asm and memory clobbers

On 11/20/2015 01:38 PM, David Wohlferd wrote: On 11/20/2015 3:14 AM, Andrew Haley wrote: On 20/11/15 10:37, David Wohlferd wrote: The intent for 24414 is to change basic asm such that it will become (quoting jeff) "an opaque blob that read/write/clobber any register or memory location." Such

Re: basic asm and memory clobbers

On 11/20/2015 2:17 AM, Andrew Haley wrote: On 20/11/15 01:23, David Wohlferd wrote: I tried to picture the most basic case I can think of that uses something clobber-able: for (int x=0; x < 1000; x++) asm("#stuff"); This generates very simple and highly performant code:

Re: basic asm and memory clobbers

On Fri, Nov 20, 2015 at 04:29:50PM +0100, Richard Henderson wrote: > On 11/20/2015 04:20 PM, Segher Boessenkool wrote: > >On Fri, Nov 20, 2015 at 02:05:01PM +0100, Richard Henderson wrote: > >>I'd be perfectly happy to deprecate and later completely remove basic asm > >>within functions. > >> >

Re: basic asm and memory clobbers

On 11/20/2015 04:34 PM, Jakub Jelinek wrote: Isn't that going to break too much code though? I mean, e.g. including libgcc... I don't know. My suspicion is very little. But that's actually what I'd like to know before we start adjusting code in other ways wrt basic asms. r~

Re: basic asm and memory clobbers

On Fri, Nov 20, 2015 at 02:05:01PM +0100, Richard Henderson wrote: > I'd be perfectly happy to deprecate and later completely remove basic asm > within functions. > > Because IMO it's essentially useless. It has no inputs, no outputs, and no > way to tell the compiler what machine state has

Re: basic asm and memory clobbers

On 11/20/2015 04:20 PM, Segher Boessenkool wrote: On Fri, Nov 20, 2015 at 02:05:01PM +0100, Richard Henderson wrote: I'd be perfectly happy to deprecate and later completely remove basic asm within functions. Because IMO it's essentially useless. It has no inputs, no outputs, and no way to

Re: basic asm and memory clobbers

On Fri, Nov 20, 2015 at 04:29:50PM +0100, Richard Henderson wrote: > >>It seems to me that it would be better to remove the feature, forcing what > >>must be an extremely small number of users to audit and update to extended > >>asm. > > > >Should asm("bla"); then be an extended asm with no

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