0507448d82
The premise here is to allow non-kernel functions to locate external LDS variables without using LDS or extra magic SGPRs to do so. 1/ First it crawls the callgraph to work out which external LDS variables are reachable from a given kernel 2/ Then it creates a new `extern char[0]` variable for each kernel, which will alias all the other extern LDS variables because that's the documented behaviour of these variables 3/ The address of that variable is written to a lookup table. The global variable is tagged with metadata to track what address it was allocated at by codegen 4/ The assembler builds the lookup table using the metadata 5/ Any non-kernel functions use the same magic intrinsic used by table lookups of non-dynamic LDS variables to find the address to use Heavy overlap with the code paths taken for other lowering, in particular the same intrinsic is used to pass the dynamic scope information through the same sgpr as for table lookups of static LDS. Reviewed By: arsenm Differential Revision: https://reviews.llvm.org/D144233
62 lines
2.7 KiB
LLVM
62 lines
2.7 KiB
LLVM
; RUN: opt -S -mtriple=amdgcn-- -amdgpu-lower-module-lds < %s | FileCheck %s
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; RUN: opt -S -mtriple=amdgcn-- -passes=amdgpu-lower-module-lds < %s | FileCheck %s
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; Variables that are not lowered by this pass are left unchanged
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; CHECK-NOT: asm
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; CHECK-NOT: llvm.amdgcn.module.lds
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; CHECK-NOT: llvm.amdgcn.module.lds.t
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; var1 is removed, var2 stays because it's in compiler.used
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; CHECK-NOT: @var1
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; CHECK: @var2 = addrspace(3) global float undef
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@var1 = addrspace(3) global i32 undef
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@var2 = addrspace(3) global float undef
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; constant variables are left to the optimizer / error diagnostics
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; CHECK: @const_undef = addrspace(3) constant i32 undef
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; CHECK: @const_with_init = addrspace(3) constant i64 8
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@const_undef = addrspace(3) constant i32 undef
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@const_with_init = addrspace(3) constant i64 8
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; Use of an addrspace(3) variable with an initializer is skipped,
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; so as to preserve the unimplemented error from llc
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; CHECK: @with_init = addrspace(3) global i64 0
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@with_init = addrspace(3) global i64 0
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; Only local addrspace variables are transformed
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; CHECK: @addr4 = addrspace(4) global i64 undef
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@addr4 = addrspace(4) global i64 undef
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; Assign to self is treated as any other initializer, i.e. ignored by this pass
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; CHECK: @toself = addrspace(3) global ptr addrspace(3) @toself, align 8
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@toself = addrspace(3) global ptr addrspace(3) @toself, align 8
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; Use by .used lists doesn't trigger lowering
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; CHECK-NOT: @llvm.used =
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@llvm.used = appending global [1 x ptr] [ptr addrspacecast (ptr addrspace(3) @var1 to ptr)], section "llvm.metadata"
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; CHECK: @llvm.compiler.used = appending global [1 x ptr] [ptr addrspacecast (ptr addrspace(3) @var2 to ptr)], section "llvm.metadata"
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@llvm.compiler.used = appending global [1 x ptr] [ptr addrspacecast (ptr addrspace(3) @var2 to ptr)], section "llvm.metadata"
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; Access from a function would cause lowering for non-excluded cases
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; CHECK-LABEL: @use_variables()
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; CHECK: %c0 = load i32, ptr addrspace(3) @const_undef, align 4
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; CHECK: %c1 = load i64, ptr addrspace(3) @const_with_init, align 4
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; CHECK: %v0 = atomicrmw add ptr addrspace(3) @with_init, i64 1 seq_cst
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; CHECK: %v1 = atomicrmw add ptr addrspace(4) @addr4, i64 %c1 monotonic
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define void @use_variables() {
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%c0 = load i32, ptr addrspace(3) @const_undef, align 4
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%c1 = load i64, ptr addrspace(3) @const_with_init, align 4
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%v0 = atomicrmw add ptr addrspace(3) @with_init, i64 1 seq_cst
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%v1 = atomicrmw add ptr addrspace(4) @addr4, i64 %c1 monotonic
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ret void
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}
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; CHECK-LABEL: @kern_use()
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; CHECK: %inc = atomicrmw add ptr addrspace(3) @llvm.amdgcn.kernel.kern_use.lds, i32 1 monotonic, align 4
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define amdgpu_kernel void @kern_use() {
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%inc = atomicrmw add ptr addrspace(3) @var1, i32 1 monotonic
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call void @use_variables()
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ret void
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}
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