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JOE1994JOE1994
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[docs][NVPTX] Use opaque pointers in IR examples (NFC) (#81941)
Replace outdated typed-pointer notation in LLVM IR examples. NFC.
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‎llvm/docs/NVPTXUsage.rst‎

Lines changed: 33 additions & 39 deletions
Original file line numberDiff line numberDiff line change
@@ -53,15 +53,15 @@ function ``@my_kernel`` is callable from host code, but ``@my_fmad`` is not.
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ret float %add
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}
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define void @my_kernel(float* %ptr) {
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%val = load float, float* %ptr
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define void @my_kernel(ptr %ptr) {
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%val = load float, ptr %ptr
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%ret = call float @my_fmad(float %val, float %val, float %val)
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store float %ret, float* %ptr
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store float %ret, ptr %ptr
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ret void
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}
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!nvvm.annotations = !{!1}
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!1 = !{void (float*)* @my_kernel, !"kernel", i32 1}
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!1 = !{ptr @my_kernel, !"kernel", i32 1}
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When compiled, the PTX kernel functions are callable by host-side code.
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@@ -140,10 +140,10 @@ These are overloaded intrinsics. You can use these on any pointer types.
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.. code-block:: llvm
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declare i8* @llvm.nvvm.ptr.global.to.gen.p0i8.p1i8(i8 addrspace(1)*)
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declare i8* @llvm.nvvm.ptr.shared.to.gen.p0i8.p3i8(i8 addrspace(3)*)
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declare i8* @llvm.nvvm.ptr.constant.to.gen.p0i8.p4i8(i8 addrspace(4)*)
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declare i8* @llvm.nvvm.ptr.local.to.gen.p0i8.p5i8(i8 addrspace(5)*)
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declare ptr @llvm.nvvm.ptr.global.to.gen.p0.p1(ptr addrspace(1))
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declare ptr @llvm.nvvm.ptr.shared.to.gen.p0.p3(ptr addrspace(3))
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declare ptr @llvm.nvvm.ptr.constant.to.gen.p0.p4(ptr addrspace(4))
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declare ptr @llvm.nvvm.ptr.local.to.gen.p0.p5(ptr addrspace(5))
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Overview:
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"""""""""
@@ -168,10 +168,10 @@ These are overloaded intrinsics. You can use these on any pointer types.
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.. code-block:: llvm
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declare i8 addrspace(1)* @llvm.nvvm.ptr.gen.to.global.p1i8.p0i8(i8*)
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declare i8 addrspace(3)* @llvm.nvvm.ptr.gen.to.shared.p3i8.p0i8(i8*)
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declare i8 addrspace(4)* @llvm.nvvm.ptr.gen.to.constant.p4i8.p0i8(i8*)
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declare i8 addrspace(5)* @llvm.nvvm.ptr.gen.to.local.p5i8.p0i8(i8*)
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declare ptr addrspace(1) @llvm.nvvm.ptr.gen.to.global.p1.p0(ptr)
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declare ptr addrspace(3) @llvm.nvvm.ptr.gen.to.shared.p3.p0(ptr)
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declare ptr addrspace(4) @llvm.nvvm.ptr.gen.to.constant.p4.p0(ptr)
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declare ptr addrspace(5) @llvm.nvvm.ptr.gen.to.local.p5.p0(ptr)
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Overview:
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"""""""""
@@ -436,35 +436,33 @@ The Kernel
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; Intrinsic to read X component of thread ID
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declare i32 @llvm.nvvm.read.ptx.sreg.tid.x() readnone nounwind
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439-
define void @kernel(float addrspace(1)* %A,
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float addrspace(1)* %B,
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float addrspace(1)* %C) {
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define void @kernel(ptr addrspace(1) %A,
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ptr addrspace(1) %B,
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ptr addrspace(1) %C) {
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entry:
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; What is my ID?
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%id = tail call i32 @llvm.nvvm.read.ptx.sreg.tid.x() readnone nounwind
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; Compute pointers into A, B, and C
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%ptrA = getelementptr float, float addrspace(1)* %A, i32 %id
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%ptrB = getelementptr float, float addrspace(1)* %B, i32 %id
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%ptrC = getelementptr float, float addrspace(1)* %C, i32 %id
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%ptrA = getelementptr float, ptr addrspace(1) %A, i32 %id
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%ptrB = getelementptr float, ptr addrspace(1) %B, i32 %id
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%ptrC = getelementptr float, ptr addrspace(1) %C, i32 %id
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; Read A, B
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%valA = load float, float addrspace(1)* %ptrA, align 4
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%valB = load float, float addrspace(1)* %ptrB, align 4
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%valA = load float, ptr addrspace(1) %ptrA, align 4
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%valB = load float, ptr addrspace(1) %ptrB, align 4
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; Compute C = A + B
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%valC = fadd float %valA, %valB
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; Store back to C
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store float %valC, float addrspace(1)* %ptrC, align 4
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store float %valC, ptr addrspace(1) %ptrC, align 4
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ret void
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}
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!nvvm.annotations = !{!0}
465-
!0 = !{void (float addrspace(1)*,
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float addrspace(1)*,
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float addrspace(1)*)* @kernel, !"kernel", i32 1}
465+
!0 = !{ptr @kernel, !"kernel", i32 1}
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We can use the LLVM ``llc`` tool to directly run the NVPTX code generator:
@@ -613,9 +611,7 @@ For the previous example, we have:
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.. code-block:: llvm
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!nvvm.annotations = !{!0}
616-
!0 = !{void (float addrspace(1)*,
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float addrspace(1)*,
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float addrspace(1)*)* @kernel, !"kernel", i32 1}
614+
!0 = !{ptr @kernel, !"kernel", i32 1}
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Here, we have a single metadata declaration in ``nvvm.annotations``. This
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metadata annotates our ``@kernel`` function with the ``kernel`` attribute.
@@ -820,35 +816,33 @@ Libdevice provides an ``__nv_powf`` function that we will use.
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; libdevice function
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declare float @__nv_powf(float, float)
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823-
define void @kernel(float addrspace(1)* %A,
824-
float addrspace(1)* %B,
825-
float addrspace(1)* %C) {
819+
define void @kernel(ptr addrspace(1) %A,
820+
ptr addrspace(1) %B,
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ptr addrspace(1) %C) {
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entry:
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; What is my ID?
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%id = tail call i32 @llvm.nvvm.read.ptx.sreg.tid.x() readnone nounwind
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; Compute pointers into A, B, and C
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%ptrA = getelementptr float, float addrspace(1)* %A, i32 %id
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%ptrB = getelementptr float, float addrspace(1)* %B, i32 %id
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%ptrC = getelementptr float, float addrspace(1)* %C, i32 %id
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%ptrA = getelementptr float, ptr addrspace(1) %A, i32 %id
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%ptrB = getelementptr float, ptr addrspace(1) %B, i32 %id
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%ptrC = getelementptr float, ptr addrspace(1) %C, i32 %id
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; Read A, B
836-
%valA = load float, float addrspace(1)* %ptrA, align 4
837-
%valB = load float, float addrspace(1)* %ptrB, align 4
832+
%valA = load float, ptr addrspace(1) %ptrA, align 4
833+
%valB = load float, ptr addrspace(1) %ptrB, align 4
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; Compute C = pow(A, B)
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%valC = call float @__nv_powf(float %valA, float %valB)
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; Store back to C
843-
store float %valC, float addrspace(1)* %ptrC, align 4
839+
store float %valC, ptr addrspace(1) %ptrC, align 4
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ret void
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}
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!nvvm.annotations = !{!0}
849-
!0 = !{void (float addrspace(1)*,
850-
float addrspace(1)*,
851-
float addrspace(1)*)* @kernel, !"kernel", i32 1}
845+
!0 = !{ptr @kernel, !"kernel", i32 1}
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To compile this kernel, we perform the following steps:

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