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[docs][NVPTX] Use opaque pointers in IR examples (NFC) #81941

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72 changes: 33 additions & 39 deletions llvm/docs/NVPTXUsage.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -53,15 +53,15 @@ function ``@my_kernel`` is callable from host code, but ``@my_fmad`` is not.
ret float %add
}

define void @my_kernel(float* %ptr) {
%val = load float, float* %ptr
define void @my_kernel(ptr %ptr) {
%val = load float, ptr %ptr
%ret = call float @my_fmad(float %val, float %val, float %val)
store float %ret, float* %ptr
store float %ret, ptr %ptr
ret void
}

!nvvm.annotations = !{!1}
!1 = !{void (float*)* @my_kernel, !"kernel", i32 1}
!1 = !{ptr @my_kernel, !"kernel", i32 1}

When compiled, the PTX kernel functions are callable by host-side code.

Expand Down Expand Up @@ -140,10 +140,10 @@ These are overloaded intrinsics. You can use these on any pointer types.

.. code-block:: llvm

declare i8* @llvm.nvvm.ptr.global.to.gen.p0i8.p1i8(i8 addrspace(1)*)
declare i8* @llvm.nvvm.ptr.shared.to.gen.p0i8.p3i8(i8 addrspace(3)*)
declare i8* @llvm.nvvm.ptr.constant.to.gen.p0i8.p4i8(i8 addrspace(4)*)
declare i8* @llvm.nvvm.ptr.local.to.gen.p0i8.p5i8(i8 addrspace(5)*)
declare ptr @llvm.nvvm.ptr.global.to.gen.p0.p1(ptr addrspace(1))
declare ptr @llvm.nvvm.ptr.shared.to.gen.p0.p3(ptr addrspace(3))
declare ptr @llvm.nvvm.ptr.constant.to.gen.p0.p4(ptr addrspace(4))
declare ptr @llvm.nvvm.ptr.local.to.gen.p0.p5(ptr addrspace(5))

Overview:
"""""""""
Expand All @@ -168,10 +168,10 @@ These are overloaded intrinsics. You can use these on any pointer types.

.. code-block:: llvm

declare i8 addrspace(1)* @llvm.nvvm.ptr.gen.to.global.p1i8.p0i8(i8*)
declare i8 addrspace(3)* @llvm.nvvm.ptr.gen.to.shared.p3i8.p0i8(i8*)
declare i8 addrspace(4)* @llvm.nvvm.ptr.gen.to.constant.p4i8.p0i8(i8*)
declare i8 addrspace(5)* @llvm.nvvm.ptr.gen.to.local.p5i8.p0i8(i8*)
declare ptr addrspace(1) @llvm.nvvm.ptr.gen.to.global.p1.p0(ptr)
declare ptr addrspace(3) @llvm.nvvm.ptr.gen.to.shared.p3.p0(ptr)
declare ptr addrspace(4) @llvm.nvvm.ptr.gen.to.constant.p4.p0(ptr)
declare ptr addrspace(5) @llvm.nvvm.ptr.gen.to.local.p5.p0(ptr)

Overview:
"""""""""
Expand Down Expand Up @@ -436,35 +436,33 @@ The Kernel
; Intrinsic to read X component of thread ID
declare i32 @llvm.nvvm.read.ptx.sreg.tid.x() readnone nounwind

define void @kernel(float addrspace(1)* %A,
float addrspace(1)* %B,
float addrspace(1)* %C) {
define void @kernel(ptr addrspace(1) %A,
ptr addrspace(1) %B,
ptr addrspace(1) %C) {
entry:
; What is my ID?
%id = tail call i32 @llvm.nvvm.read.ptx.sreg.tid.x() readnone nounwind

; Compute pointers into A, B, and C
%ptrA = getelementptr float, float addrspace(1)* %A, i32 %id
%ptrB = getelementptr float, float addrspace(1)* %B, i32 %id
%ptrC = getelementptr float, float addrspace(1)* %C, i32 %id
%ptrA = getelementptr float, ptr addrspace(1) %A, i32 %id
%ptrB = getelementptr float, ptr addrspace(1) %B, i32 %id
%ptrC = getelementptr float, ptr addrspace(1) %C, i32 %id

; Read A, B
%valA = load float, float addrspace(1)* %ptrA, align 4
%valB = load float, float addrspace(1)* %ptrB, align 4
%valA = load float, ptr addrspace(1) %ptrA, align 4
%valB = load float, ptr addrspace(1) %ptrB, align 4

; Compute C = A + B
%valC = fadd float %valA, %valB

; Store back to C
store float %valC, float addrspace(1)* %ptrC, align 4
store float %valC, ptr addrspace(1) %ptrC, align 4

ret void
}

!nvvm.annotations = !{!0}
!0 = !{void (float addrspace(1)*,
float addrspace(1)*,
float addrspace(1)*)* @kernel, !"kernel", i32 1}
!0 = !{ptr @kernel, !"kernel", i32 1}


We can use the LLVM ``llc`` tool to directly run the NVPTX code generator:
Expand Down Expand Up @@ -613,9 +611,7 @@ For the previous example, we have:
.. code-block:: llvm

!nvvm.annotations = !{!0}
!0 = !{void (float addrspace(1)*,
float addrspace(1)*,
float addrspace(1)*)* @kernel, !"kernel", i32 1}
!0 = !{ptr @kernel, !"kernel", i32 1}

Here, we have a single metadata declaration in ``nvvm.annotations``. This
metadata annotates our ``@kernel`` function with the ``kernel`` attribute.
Expand Down Expand Up @@ -820,35 +816,33 @@ Libdevice provides an ``__nv_powf`` function that we will use.
; libdevice function
declare float @__nv_powf(float, float)

define void @kernel(float addrspace(1)* %A,
float addrspace(1)* %B,
float addrspace(1)* %C) {
define void @kernel(ptr addrspace(1) %A,
ptr addrspace(1) %B,
ptr addrspace(1) %C) {
entry:
; What is my ID?
%id = tail call i32 @llvm.nvvm.read.ptx.sreg.tid.x() readnone nounwind

; Compute pointers into A, B, and C
%ptrA = getelementptr float, float addrspace(1)* %A, i32 %id
%ptrB = getelementptr float, float addrspace(1)* %B, i32 %id
%ptrC = getelementptr float, float addrspace(1)* %C, i32 %id
%ptrA = getelementptr float, ptr addrspace(1) %A, i32 %id
%ptrB = getelementptr float, ptr addrspace(1) %B, i32 %id
%ptrC = getelementptr float, ptr addrspace(1) %C, i32 %id

; Read A, B
%valA = load float, float addrspace(1)* %ptrA, align 4
%valB = load float, float addrspace(1)* %ptrB, align 4
%valA = load float, ptr addrspace(1) %ptrA, align 4
%valB = load float, ptr addrspace(1) %ptrB, align 4

; Compute C = pow(A, B)
%valC = call float @__nv_powf(float %valA, float %valB)

; Store back to C
store float %valC, float addrspace(1)* %ptrC, align 4
store float %valC, ptr addrspace(1) %ptrC, align 4

ret void
}

!nvvm.annotations = !{!0}
!0 = !{void (float addrspace(1)*,
float addrspace(1)*,
float addrspace(1)*)* @kernel, !"kernel", i32 1}
!0 = !{ptr @kernel, !"kernel", i32 1}


To compile this kernel, we perform the following steps:
Expand Down