Cameron McInally via llvm-dev
2020-Jul-07 15:10 UTC
[llvm-dev] BUILD_VECTOR disambiguation
Thanks for the clarification. The `except` seemed dangling to me, but it's early here. Just curious... how do we end up with a mixed type BUILD_VECTOR? That's counterintuitive. On Tue, Jul 7, 2020 at 10:58 AM Krzysztof Parzyszek via llvm-dev <llvm-dev at lists.llvm.org> wrote:> > Mixed integer types are ok, but the values will get truncated to the element type of the output value. It's pretty much what the comment says. > > -- > Krzysztof Parzyszek kparzysz at quicinc.com AI tools development > > > -----Original Message----- > > From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Cameron > > McInally via llvm-dev > > Sent: Tuesday, July 7, 2020 9:53 AM > > To: LLVM Developers Mailing List <llvm-dev at lists.llvm.org> > > Subject: [EXT] [llvm-dev] BUILD_VECTOR disambiguation > > > > Hey devs, > > > > From ISDOpcodes.h... > > > > /// BUILD_VECTOR(ELT0, ELT1, ELT2, ELT3,...) - Return a fixed-width vector > > /// with the specified, possibly variable, elements. The number of elements > > /// is required to be a power of two. The types of the operands must all be > > /// the same and must match the vector element type, except that integer > > types /// are allowed to be larger than the element type, in which case the > > operands /// are implicitly truncated. > > BUILD_VECTOR, > > > > Must the operand types always be the same? Or could we see a BUILD_VECTOR > > with mixed integer types? E.g.: > > > > BUILD_VECTOR(i32, i32, i64, i32) > > > > Thanks, > > Cam
Cameron McInally via llvm-dev
2020-Jul-07 15:12 UTC
[llvm-dev] BUILD_VECTOR disambiguation
Sorry. Being pedantic, how do we end up with a mixed operand type BUILD_VECTOR? On Tue, Jul 7, 2020 at 11:10 AM Cameron McInally <cameron.mcinally at nyu.edu> wrote:> > Thanks for the clarification. The `except` seemed dangling to me, but > it's early here. > > Just curious... how do we end up with a mixed type BUILD_VECTOR? > That's counterintuitive. > > On Tue, Jul 7, 2020 at 10:58 AM Krzysztof Parzyszek via llvm-dev > <llvm-dev at lists.llvm.org> wrote: > > > > Mixed integer types are ok, but the values will get truncated to the element type of the output value. It's pretty much what the comment says. > > > > -- > > Krzysztof Parzyszek kparzysz at quicinc.com AI tools development > > > > > -----Original Message----- > > > From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Cameron > > > McInally via llvm-dev > > > Sent: Tuesday, July 7, 2020 9:53 AM > > > To: LLVM Developers Mailing List <llvm-dev at lists.llvm.org> > > > Subject: [EXT] [llvm-dev] BUILD_VECTOR disambiguation > > > > > > Hey devs, > > > > > > From ISDOpcodes.h... > > > > > > /// BUILD_VECTOR(ELT0, ELT1, ELT2, ELT3,...) - Return a fixed-width vector > > > /// with the specified, possibly variable, elements. The number of elements > > > /// is required to be a power of two. The types of the operands must all be > > > /// the same and must match the vector element type, except that integer > > > types /// are allowed to be larger than the element type, in which case the > > > operands /// are implicitly truncated. > > > BUILD_VECTOR, > > > > > > Must the operand types always be the same? Or could we see a BUILD_VECTOR > > > with mixed integer types? E.g.: > > > > > > BUILD_VECTOR(i32, i32, i64, i32) > > > > > > Thanks, > > > Cam
Krzysztof Parzyszek via llvm-dev
2020-Jul-07 15:25 UTC
[llvm-dev] BUILD_VECTOR disambiguation
The problem can happen when you want to build a vector of i8, but i8 itself is not legal on your target. All operands to BUILD_VECTOR will be legalized to the next legal integer type, so you can end up with a BUILD_VECTOR of vNi8 where all operands are i32, for example. Actual mixed types are less likely to happen, but if you are doing your own target-specific lowering, you can end up with mixed types, simply because your code doesn't have to make them all the same. -- Krzysztof Parzyszek kparzysz at quicinc.com AI tools development> -----Original Message----- > From: Cameron McInally <cameron.mcinally at nyu.edu> > Sent: Tuesday, July 7, 2020 10:10 AM > To: Krzysztof Parzyszek <kparzysz at quicinc.com> > Cc: llvm-dev at lists.llvm.org > Subject: [EXT] Re: [llvm-dev] BUILD_VECTOR disambiguation > > Thanks for the clarification. The `except` seemed dangling to me, but it's > early here. > > Just curious... how do we end up with a mixed type BUILD_VECTOR? > That's counterintuitive. > > On Tue, Jul 7, 2020 at 10:58 AM Krzysztof Parzyszek via llvm-dev <llvm- > dev at lists.llvm.org> wrote: > > > > Mixed integer types are ok, but the values will get truncated to the > element type of the output value. It's pretty much what the comment says. > > > > -- > > Krzysztof Parzyszek kparzysz at quicinc.com AI tools development > > > > > -----Original Message----- > > > From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of > > > Cameron McInally via llvm-dev > > > Sent: Tuesday, July 7, 2020 9:53 AM > > > To: LLVM Developers Mailing List <llvm-dev at lists.llvm.org> > > > Subject: [EXT] [llvm-dev] BUILD_VECTOR disambiguation > > > > > > Hey devs, > > > > > > From ISDOpcodes.h... > > > > > > /// BUILD_VECTOR(ELT0, ELT1, ELT2, ELT3,...) - Return a fixed-width > > > vector /// with the specified, possibly variable, elements. The > > > number of elements /// is required to be a power of two. The types > > > of the operands must all be /// the same and must match the vector > > > element type, except that integer types /// are allowed to be larger > > > than the element type, in which case the operands /// are implicitly > truncated. > > > BUILD_VECTOR, > > > > > > Must the operand types always be the same? Or could we see a > > > BUILD_VECTOR with mixed integer types? E.g.: > > > > > > BUILD_VECTOR(i32, i32, i64, i32) > > > > > > Thanks, > > > Cam
Mixed types aren't allowed. They are checked for in VerifySDNode in SelectionDAG.cpp and will fail an asserts build. ~Craig On Tue, Jul 7, 2020 at 8:25 AM Krzysztof Parzyszek via llvm-dev < llvm-dev at lists.llvm.org> wrote:> The problem can happen when you want to build a vector of i8, but i8 > itself is not legal on your target. All operands to BUILD_VECTOR will be > legalized to the next legal integer type, so you can end up with a > BUILD_VECTOR of vNi8 where all operands are i32, for example. > > Actual mixed types are less likely to happen, but if you are doing your > own target-specific lowering, you can end up with mixed types, simply > because your code doesn't have to make them all the same. > > -- > Krzysztof Parzyszek kparzysz at quicinc.com AI tools development > > > -----Original Message----- > > From: Cameron McInally <cameron.mcinally at nyu.edu> > > Sent: Tuesday, July 7, 2020 10:10 AM > > To: Krzysztof Parzyszek <kparzysz at quicinc.com> > > Cc: llvm-dev at lists.llvm.org > > Subject: [EXT] Re: [llvm-dev] BUILD_VECTOR disambiguation > > > > Thanks for the clarification. The `except` seemed dangling to me, but > it's > > early here. > > > > Just curious... how do we end up with a mixed type BUILD_VECTOR? > > That's counterintuitive. > > > > On Tue, Jul 7, 2020 at 10:58 AM Krzysztof Parzyszek via llvm-dev <llvm- > > dev at lists.llvm.org> wrote: > > > > > > Mixed integer types are ok, but the values will get truncated to the > > element type of the output value. It's pretty much what the comment > says. > > > > > > -- > > > Krzysztof Parzyszek kparzysz at quicinc.com AI tools development > > > > > > > -----Original Message----- > > > > From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of > > > > Cameron McInally via llvm-dev > > > > Sent: Tuesday, July 7, 2020 9:53 AM > > > > To: LLVM Developers Mailing List <llvm-dev at lists.llvm.org> > > > > Subject: [EXT] [llvm-dev] BUILD_VECTOR disambiguation > > > > > > > > Hey devs, > > > > > > > > From ISDOpcodes.h... > > > > > > > > /// BUILD_VECTOR(ELT0, ELT1, ELT2, ELT3,...) - Return a fixed-width > > > > vector /// with the specified, possibly variable, elements. The > > > > number of elements /// is required to be a power of two. The types > > > > of the operands must all be /// the same and must match the vector > > > > element type, except that integer types /// are allowed to be larger > > > > than the element type, in which case the operands /// are implicitly > > truncated. > > > > BUILD_VECTOR, > > > > > > > > Must the operand types always be the same? Or could we see a > > > > BUILD_VECTOR with mixed integer types? E.g.: > > > > > > > > BUILD_VECTOR(i32, i32, i64, i32) > > > > > > > > Thanks, > > > > Cam > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20200707/cfef468b/attachment.html>