Villmow, Micah
2012-Jul-17 22:24 UTC
[LLVMdev] Switching between sibling/cousin registers via API calls
I have a register hierarchy that looks like a binary tree. v4 -> {v2, v2} -> {s, s}{s, s}(or, {x, y}, {z, w}) I have an instruction that can access the 2nd and/or 4th scalar and an instruction that can access the 1st and/or 3rd scalar. What I need to do is that given the first scalar, I need to be able to select the 2nd scalar, or/and given the 3rd, select the 4th. I define a sibling register as a register that has the same parent and a cousin as a register that has the same grandparent. So 'x' is a cousin of 'w' because of the grandparent class and 'x' is a sibling of 'y' because of the parent class. I know I can move to parent/children registers via super/sub classes, but is there any way in LLVM currently to easily select a cousin/sibling registers that I am not seeing? Currently what I've found to work is I do register - base_scalar_1 + base_scalar_2, but this doesn't seem like the best solution since this has an implicit assumption on the ordering of the enumerated register values. Any ideas? Thanks, Micah -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20120717/bec9c90a/attachment.html>
Jim Grosbach
2012-Jul-17 22:50 UTC
[LLVMdev] Switching between sibling/cousin registers via API calls
Hi Micah, This sounds somewhat similar to what ARM uses for the stride-by-two vector load instructions. For example, Tuples2DSpc. While not exactly what you're looking for, perhaps something along those lines would work? -Jim On Jul 17, 2012, at 3:24 PM, "Villmow, Micah" <Micah.Villmow at amd.com> wrote:> I have a register hierarchy that looks like a binary tree. > v4 -> {v2, v2} -> {s, s}{s, s}(or, {x, y}, {z, w}) > > I have an instruction that can access the 2nd and/or 4th scalar and an > instruction that can access the 1st and/or 3rd scalar. What I need to do > is that given the first scalar, I need to be able to select the 2nd scalar, > or/and given the 3rd, select the 4th. I define a sibling register as a register > that has the same parent and a cousin as a register that has the same grandparent. > So 'x' is a cousin of 'w' because of the grandparent class and 'x' is a sibling > of 'y' because of the parent class. > > I know I can move to parent/children registers via super/sub classes, > but is there any way in LLVM currently to easily select a cousin/sibling registers that > I am not seeing? > > Currently what I've found to work is I do register - base_scalar_1 + base_scalar_2, > but this doesn't seem like the best solution since this has an implicit > assumption on the ordering of the enumerated register values. > > Any ideas? > > Thanks, > Micah > > > _______________________________________________ > LLVM Developers mailing list > LLVMdev at cs.uiuc.edu http://llvm.cs.uiuc.edu > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20120717/52bb85bb/attachment.html>
Villmow, Micah
2012-Jul-17 23:05 UTC
[LLVMdev] Switching between sibling/cousin registers via API calls
This looks interesting, my next question would be, how do you access them? For example, let us say I know that I am register that is within a Tuples2DSpc register class, how would I be able to select the opposite register? I think the difference here is that I don't want to use both of them at the same time, I want to use one register in one instruction, and its sibling register in the next instruction. From: Jim Grosbach [mailto:grosbach at apple.com] Sent: Tuesday, July 17, 2012 3:51 PM To: Villmow, Micah Cc: Developers Mailing List Subject: Re: [LLVMdev] Switching between sibling/cousin registers via API calls Hi Micah, This sounds somewhat similar to what ARM uses for the stride-by-two vector load instructions. For example, Tuples2DSpc. While not exactly what you're looking for, perhaps something along those lines would work? -Jim On Jul 17, 2012, at 3:24 PM, "Villmow, Micah" <Micah.Villmow at amd.com<mailto:Micah.Villmow at amd.com>> wrote: I have a register hierarchy that looks like a binary tree. v4 -> {v2, v2} -> {s, s}{s, s}(or, {x, y}, {z, w}) I have an instruction that can access the 2nd and/or 4th scalar and an instruction that can access the 1st and/or 3rd scalar. What I need to do is that given the first scalar, I need to be able to select the 2nd scalar, or/and given the 3rd, select the 4th. I define a sibling register as a register that has the same parent and a cousin as a register that has the same grandparent. So 'x' is a cousin of 'w' because of the grandparent class and 'x' is a sibling of 'y' because of the parent class. I know I can move to parent/children registers via super/sub classes, but is there any way in LLVM currently to easily select a cousin/sibling registers that I am not seeing? Currently what I've found to work is I do register - base_scalar_1 + base_scalar_2, but this doesn't seem like the best solution since this has an implicit assumption on the ordering of the enumerated register values. Any ideas? Thanks, Micah _______________________________________________ LLVM Developers mailing list LLVMdev at cs.uiuc.edu<mailto:LLVMdev at cs.uiuc.edu> http://llvm.cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20120717/3b671fa0/attachment.html>
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