Files
clang-p2996/llvm/test/CodeGen/AMDGPU/control-flow-fastregalloc.ll
Christudasan Devadasan 40ba0942e2 [AMDGPU][SILowerSGPRSpills] Spill SGPRs to virtual VGPRs
Currently, the custom SGPR spill lowering pass spills
SGPRs into physical VGPR lanes and the remaining VGPRs
are used by regalloc for vector regclass allocation.
This imposes many restrictions that we ended up with
unsuccessful SGPR spilling when there won't be enough
VGPRs and we are forced to spill the leftover into
memory during PEI. The custom spill handling during PEI
has many edge cases and often breaks the compiler time
to time.

This patch implements spilling SGPRs into virtual VGPR
lanes. Since we now split the register allocation for
SGPRs and VGPRs, the virtual registers introduced for
the spill lanes would get allocated automatically in
the subsequent regalloc invocation for VGPRs.

Spill to virtual registers will always be successful,
even in the high-pressure situations, and hence it avoids
most of the edge cases during PEI. We are now left with
only the custom SGPR spills during PEI for special registers
like the frame pointer which isn an unproblematic case.

This patch also implements the whole wave spills which
might occur if RA spills any live range of virtual registers
involved in the whole wave operations. Earlier, we had
been hand-picking registers for such machine operands.
But now with SGPR spills into virtual VGPR lanes, we are
exposing them to the allocator.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D124196
2022-12-17 11:56:32 +05:30

274 lines
12 KiB
LLVM

; RUN: llc -O0 -mtriple=amdgcn--amdhsa -march=amdgcn --amdhsa-code-object-version=2 -amdgpu-spill-sgpr-to-vgpr=0 -verify-machineinstrs < %s | FileCheck -enable-var-scope -check-prefix=VMEM -check-prefix=GCN %s
; RUN: llc -O0 -mtriple=amdgcn--amdhsa -march=amdgcn --amdhsa-code-object-version=2 -amdgpu-spill-sgpr-to-vgpr=1 -verify-machineinstrs < %s | FileCheck -enable-var-scope -check-prefix=VGPR -check-prefix=GCN %s
; Verify registers used for tracking exec mask changes when all
; registers are spilled at the end of the block. The SGPR spill
; placement relative to the exec modifications are important.
; FIXME: This checks with SGPR to VGPR spilling disabled, but this may
; not work correctly in cases where no workitems take a branch.
; GCN-LABEL: {{^}}divergent_if_endif:
; VGPR: workitem_private_segment_byte_size = 16{{$}}
; GCN: {{^}}; %bb.0:
; GCN: s_mov_b32 m0, -1
; GCN: ds_read_b32 [[LOAD0:v[0-9]+]]
; Spill load
; GCN: buffer_store_dword [[LOAD0]], off, s[0:3], 0 offset:[[LOAD0_OFFSET:[0-9]+]] ; 4-byte Folded Spill
; GCN: v_cmp_eq_u32_e64 [[CMP0:s\[[0-9]+:[0-9]\]]], v{{[0-9]+}}, s{{[0-9]+}}
; Spill saved exec
; GCN: s_mov_b64 s[[[SAVEEXEC_LO:[0-9]+]]:[[SAVEEXEC_HI:[0-9]+]]], exec
; VGPR: v_writelane_b32 [[SPILL_VGPR:v[0-9]+]], s[[SAVEEXEC_LO]], [[SAVEEXEC_LO_LANE:[0-9]+]]
; VGPR: v_writelane_b32 [[SPILL_VGPR]], s[[SAVEEXEC_HI]], [[SAVEEXEC_HI_LANE:[0-9]+]]
; VMEM: v_writelane_b32 v[[V_SAVEEXEC:[0-9]+]], s[[SAVEEXEC_LO]], 0
; VMEM: v_writelane_b32 v[[V_SAVEEXEC]], s[[SAVEEXEC_HI]], 1
; VMEM: buffer_store_dword v[[V_SAVEEXEC]], off, s[0:3], 0 offset:[[V_EXEC_SPILL_OFFSET:[0-9]+]] ; 4-byte Folded Spill
; GCN: s_and_b64 s[[[ANDEXEC_LO:[0-9]+]]:[[ANDEXEC_HI:[0-9]+]]], s[[[SAVEEXEC_LO]]:[[SAVEEXEC_HI]]], [[CMP0]]
; GCN: s_mov_b64 exec, s[[[ANDEXEC_LO]]:[[ANDEXEC_HI]]]
; GCN: s_cbranch_execz [[ENDIF:.LBB[0-9]+_[0-9]+]]
; GCN: ; %bb.{{[0-9]+}}: ; %if
; GCN: buffer_load_dword [[RELOAD_LOAD0:v[0-9]+]], off, s[0:3], 0 offset:[[LOAD0_OFFSET]] ; 4-byte Folded Reload
; GCN: s_mov_b32 m0, -1
; GCN: ds_read_b32 [[LOAD1:v[0-9]+]]
; GCN: s_waitcnt vmcnt(0) lgkmcnt(0)
; Spill val register
; GCN: v_add_i32_e32 [[VAL:v[0-9]+]], vcc, [[LOAD1]], [[RELOAD_LOAD0]]
; GCN: buffer_store_dword [[VAL]], off, s[0:3], 0 offset:[[VAL_OFFSET:[0-9]+]] ; 4-byte Folded Spill
; VMEM: [[ENDIF]]:
; Restore val
; GCN: buffer_load_dword [[RELOAD_VAL:v[0-9]+]], off, s[0:3], 0 offset:[[VAL_OFFSET]] ; 4-byte Folded Reload
; Reload and restore exec mask
; VGPR: v_readlane_b32 s[[S_RELOAD_SAVEEXEC_LO:[0-9]+]], [[SPILL_VGPR]], [[SAVEEXEC_LO_LANE]]
; VGPR: v_readlane_b32 s[[S_RELOAD_SAVEEXEC_HI:[0-9]+]], [[SPILL_VGPR]], [[SAVEEXEC_HI_LANE]]
; VMEM: buffer_load_dword v[[V_RELOAD_SAVEEXEC:[0-9]+]], off, s[0:3], 0 offset:[[V_EXEC_SPILL_OFFSET]] ; 4-byte Folded Reload
; VMEM: s_waitcnt vmcnt(0)
; VMEM: v_readlane_b32 s[[S_RELOAD_SAVEEXEC_LO:[0-9]+]], v[[V_RELOAD_SAVEEXEC]], 0
; VMEM: v_readlane_b32 s[[S_RELOAD_SAVEEXEC_HI:[0-9]+]], v[[V_RELOAD_SAVEEXEC]], 1
; GCN: s_or_b64 exec, exec, s[[[S_RELOAD_SAVEEXEC_LO]]:[[S_RELOAD_SAVEEXEC_HI]]]
; GCN: flat_store_dword v{{\[[0-9]+:[0-9]+\]}}, [[RELOAD_VAL]]
define amdgpu_kernel void @divergent_if_endif(i32 addrspace(1)* %out) #0 {
entry:
%tid = call i32 @llvm.amdgcn.workitem.id.x()
%load0 = load volatile i32, i32 addrspace(3)* undef
%cmp0 = icmp eq i32 %tid, 0
br i1 %cmp0, label %if, label %endif
if:
%load1 = load volatile i32, i32 addrspace(3)* undef
%val = add i32 %load0, %load1
br label %endif
endif:
%tmp4 = phi i32 [ %val, %if ], [ 0, %entry ]
store i32 %tmp4, i32 addrspace(1)* %out
ret void
}
; GCN-LABEL: {{^}}divergent_loop:
; VGPR: workitem_private_segment_byte_size = 20{{$}}
; GCN: {{^}}; %bb.0:
; GCN-DAG: s_mov_b32 m0, -1
; GCN-DAG: v_mov_b32_e32 [[PTR0:v[0-9]+]], 0{{$}}
; GCN: ds_read_b32 [[LOAD0:v[0-9]+]], [[PTR0]]
; GCN: v_cmp_eq_u32_e64 [[CMP0:s\[[0-9]+:[0-9]+\]]], v{{[0-9]+}}, s{{[0-9]+}}
; Spill load
; GCN: buffer_store_dword [[LOAD0]], off, s[0:3], 0 offset:[[LOAD0_OFFSET:[0-9]+]] ; 4-byte Folded Spill
; GCN: s_mov_b64 s[[[SAVEEXEC_LO:[0-9]+]]:[[SAVEEXEC_HI:[0-9]+]]], exec
; Spill saved exec
; VGPR: v_writelane_b32 [[SPILL_VGPR:v[0-9]+]], s[[SAVEEXEC_LO]], [[SAVEEXEC_LO_LANE:[0-9]+]]
; VGPR: v_writelane_b32 [[SPILL_VGPR]], s[[SAVEEXEC_HI]], [[SAVEEXEC_HI_LANE:[0-9]+]]
; VMEM: v_writelane_b32 v[[V_SAVEEXEC:[0-9]+]], s[[SAVEEXEC_LO]], 0
; VMEM: v_writelane_b32 v[[V_SAVEEXEC]], s[[SAVEEXEC_HI]], 1
; VMEM: buffer_store_dword v[[V_SAVEEXEC]], off, s[0:3], 0 offset:[[V_EXEC_SPILL_OFFSET:[0-9]+]] ; 4-byte Folded Spill
; GCN: s_and_b64 s[[[ANDEXEC_LO:[0-9]+]]:[[ANDEXEC_HI:[0-9]+]]], s[[[SAVEEXEC_LO:[0-9]+]]:[[SAVEEXEC_HI:[0-9]+]]], [[CMP0]]
; GCN: s_mov_b64 exec, s[[[ANDEXEC_LO]]:[[ANDEXEC_HI]]]
; GCN-NEXT: s_cbranch_execz [[END:.LBB[0-9]+_[0-9]+]]
; GCN: [[LOOP:.LBB[0-9]+_[0-9]+]]:
; GCN: buffer_load_dword v[[VAL_LOOP_RELOAD:[0-9]+]], off, s[0:3], 0 offset:[[LOAD0_OFFSET]] ; 4-byte Folded Reload
; GCN: v_subrev_i32_e32 [[VAL_LOOP:v[0-9]+]], vcc, v{{[0-9]+}}, v[[VAL_LOOP_RELOAD]]
; GCN: s_cmp_lg_u32
; VMEM: buffer_store_dword
; VMEM: buffer_store_dword
; VMEM: buffer_store_dword
; GCN: buffer_store_dword [[VAL_LOOP]], off, s[0:3], 0 offset:{{[0-9]+}} ; 4-byte Folded Spill
; GCN-NEXT: s_cbranch_scc1 [[LOOP]]
; GCN: buffer_store_dword [[VAL_LOOP]], off, s[0:3], 0 offset:[[VAL_SUB_OFFSET:[0-9]+]] ; 4-byte Folded Spill
; GCN: [[END]]:
; GCN: buffer_load_dword v[[VAL_END:[0-9]+]], off, s[0:3], 0 offset:[[VAL_SUB_OFFSET]] ; 4-byte Folded Reload
; VGPR: v_readlane_b32 s[[S_RELOAD_SAVEEXEC_LO:[0-9]+]], [[SPILL_VGPR]], [[SAVEEXEC_LO_LANE]]
; VGPR: v_readlane_b32 s[[S_RELOAD_SAVEEXEC_HI:[0-9]+]], [[SPILL_VGPR]], [[SAVEEXEC_HI_LANE]]
; VMEM: buffer_load_dword v[[V_RELOAD_SAVEEXEC:[0-9]+]], off, s[0:3], 0 offset:[[V_EXEC_SPILL_OFFSET]] ; 4-byte Folded Reload
; VMEM: s_waitcnt vmcnt(0)
; VMEM: v_readlane_b32 s[[S_RELOAD_SAVEEXEC_LO:[0-9]+]], v[[V_RELOAD_SAVEEXEC]], 0
; VMEM: v_readlane_b32 s[[S_RELOAD_SAVEEXEC_HI:[0-9]+]], v[[V_RELOAD_SAVEEXEC]], 1
; GCN: s_or_b64 exec, exec, s[[[S_RELOAD_SAVEEXEC_LO]]:[[S_RELOAD_SAVEEXEC_HI]]]
; GCN: flat_store_dword v{{\[[0-9]+:[0-9]+\]}}, v[[VAL_END]]
define amdgpu_kernel void @divergent_loop(i32 addrspace(1)* %out) #0 {
entry:
%tid = call i32 @llvm.amdgcn.workitem.id.x()
%load0 = load volatile i32, i32 addrspace(3)* null
%cmp0 = icmp eq i32 %tid, 0
br i1 %cmp0, label %loop, label %end
loop:
%i = phi i32 [ %i.inc, %loop ], [ 0, %entry ]
%val = phi i32 [ %val.sub, %loop ], [ %load0, %entry ]
%load1 = load volatile i32, i32 addrspace(3)* undef
%i.inc = add i32 %i, 1
%val.sub = sub i32 %val, %load1
%cmp1 = icmp ne i32 %i, 256
br i1 %cmp1, label %loop, label %end
end:
%tmp4 = phi i32 [ %val.sub, %loop ], [ 0, %entry ]
store i32 %tmp4, i32 addrspace(1)* %out
ret void
}
; GCN-LABEL: {{^}}divergent_if_else_endif:
; GCN: {{^}}; %bb.0:
; GCN-DAG: s_mov_b32 m0, -1
; GCN-DAG: v_mov_b32_e32 [[PTR0:v[0-9]+]], 0{{$}}
; GCN: ds_read_b32 [[LOAD0:v[0-9]+]], [[PTR0]]
; Spill load
; GCN: buffer_store_dword [[LOAD0]], off, s[0:3], 0 offset:[[LOAD0_OFFSET:[0-9]+]] ; 4-byte Folded Spill
; GCN: s_mov_b32 [[ZERO:s[0-9]+]], 0
; GCN: v_cmp_ne_u32_e64 [[CMP0:s\[[0-9]+:[0-9]\]]], v{{[0-9]+}}, [[ZERO]]
; GCN: s_mov_b64 s[[[SAVEEXEC_LO:[0-9]+]]:[[SAVEEXEC_HI:[0-9]+]]], exec
; GCN: s_and_b64 s[[[ANDEXEC_LO:[0-9]+]]:[[ANDEXEC_HI:[0-9]+]]], s[[[SAVEEXEC_LO:[0-9]+]]:[[SAVEEXEC_HI:[0-9]+]]], [[CMP0]]
; GCN: s_xor_b64 s[[[SAVEEXEC_LO]]:[[SAVEEXEC_HI]]], s[[[ANDEXEC_LO]]:[[ANDEXEC_HI]]], s[[[SAVEEXEC_LO]]:[[SAVEEXEC_HI]]]
; Spill saved exec
; VGPR: v_writelane_b32 [[SPILL_VGPR:v[0-9]+]], s[[SAVEEXEC_LO]], [[SAVEEXEC_LO_LANE:[0-9]+]]
; VGPR: v_writelane_b32 [[SPILL_VGPR]], s[[SAVEEXEC_HI]], [[SAVEEXEC_HI_LANE:[0-9]+]]
; VMEM: v_writelane_b32 v[[V_SAVEEXEC:[0-9]+]], s[[SAVEEXEC_LO]], 0
; VMEM: v_writelane_b32 v[[V_SAVEEXEC]], s[[SAVEEXEC_HI]], 1
; VMEM: buffer_store_dword v[[V_SAVEEXEC]], off, s[0:3], 0 offset:[[SAVEEXEC_OFFSET:[0-9]+]] ; 4-byte Folded Spill
; GCN: s_mov_b64 exec, [[CMP0]]
; FIXME: It makes no sense to put this skip here
; GCN: s_cbranch_execz [[FLOW:.LBB[0-9]+_[0-9]+]]
; GCN-NEXT: s_branch [[ELSE:.LBB[0-9]+_[0-9]+]]
; GCN: [[FLOW]]: ; %Flow
; VGPR: buffer_load_dword
; GCN: buffer_load_dword [[FLOW_VAL:v[0-9]+]], off, s[0:3], 0 offset:[[FLOW_VAL_OFFSET:[0-9]+]] ; 4-byte Folded Reload
; VGPR: v_readlane_b32 s[[FLOW_S_RELOAD_SAVEEXEC_LO:[0-9]+]], [[SPILL_VGPR]], [[SAVEEXEC_LO_LANE]]
; VGPR: v_readlane_b32 s[[FLOW_S_RELOAD_SAVEEXEC_HI:[0-9]+]], [[SPILL_VGPR]], [[SAVEEXEC_HI_LANE]]
; VMEM: buffer_load_dword v[[FLOW_V_RELOAD_SAVEEXEC:[0-9]+]], off, s[0:3], 0 offset:[[SAVEEXEC_OFFSET]]
; VMEM: s_waitcnt vmcnt(0)
; VMEM: v_readlane_b32 s[[FLOW_S_RELOAD_SAVEEXEC_LO:[0-9]+]], v[[FLOW_V_RELOAD_SAVEEXEC]], 0
; VMEM: v_readlane_b32 s[[FLOW_S_RELOAD_SAVEEXEC_HI:[0-9]+]], v[[FLOW_V_RELOAD_SAVEEXEC]], 1
; GCN: s_or_saveexec_b64 s[[[FLOW_S_RELOAD_SAVEEXEC_LO_SAVEEXEC:[0-9]+]]:[[FLOW_S_RELOAD_SAVEEXEC_HI_SAVEEXEC:[0-9]+]]], s[[[FLOW_S_RELOAD_SAVEEXEC_LO]]:[[FLOW_S_RELOAD_SAVEEXEC_HI]]]
; Regular spill value restored after exec modification
; Followed by spill
; GCN: buffer_store_dword [[FLOW_VAL]], off, s[0:3], 0 offset:[[RESULT_OFFSET:[0-9]+]] ; 4-byte Folded Spill
; GCN: s_and_b64 s[[[FLOW_AND_EXEC_LO:[0-9]+]]:[[FLOW_AND_EXEC_HI:[0-9]+]]], exec, s[[[FLOW_S_RELOAD_SAVEEXEC_LO_SAVEEXEC]]:[[FLOW_S_RELOAD_SAVEEXEC_HI_SAVEEXEC]]]
; Spill saved exec
; VGPR: v_writelane_b32 [[SPILL_VGPR]], s[[FLOW_AND_EXEC_LO]], [[FLOW_SAVEEXEC_LO_LANE:[0-9]+]]
; VGPR: v_writelane_b32 [[SPILL_VGPR]], s[[FLOW_AND_EXEC_HI]], [[FLOW_SAVEEXEC_HI_LANE:[0-9]+]]
; VMEM: v_writelane_b32 v[[FLOW_V_SAVEEXEC:[0-9]+]], s[[FLOW_AND_EXEC_LO]], 0
; VMEM: v_writelane_b32 v[[FLOW_V_SAVEEXEC]], s[[FLOW_AND_EXEC_HI]], 1
; VMEM: buffer_store_dword v[[FLOW_V_SAVEEXEC]], off, s[0:3], 0 offset:[[FLOW_SAVEEXEC_OFFSET:[0-9]+]] ; 4-byte Folded Spill
; GCN: s_xor_b64 exec, exec, s[[[FLOW_AND_EXEC_LO]]:[[FLOW_AND_EXEC_HI]]]
; GCN-NEXT: s_cbranch_execz [[ENDIF:.LBB[0-9]+_[0-9]+]]
; GCN: ; %bb.{{[0-9]+}}: ; %if
; GCN: buffer_load_dword v[[LOAD0_RELOAD:[0-9]+]], off, s[0:3], 0 offset:[[LOAD0_OFFSET]] ; 4-byte Folded Reload
; GCN: ds_read_b32
; GCN: v_add_i32_e32 [[ADD:v[0-9]+]], vcc, v{{[0-9]+}}, v[[LOAD0_RELOAD]]
; GCN: buffer_store_dword [[ADD]], off, s[0:3], 0 offset:[[RESULT_OFFSET]] ; 4-byte Folded Spill
; GCN-NEXT: s_branch [[ENDIF:.LBB[0-9]+_[0-9]+]]
; GCN: [[ELSE]]: ; %else
; GCN: buffer_load_dword v[[LOAD0_RELOAD:[0-9]+]], off, s[0:3], 0 offset:[[LOAD0_OFFSET]] ; 4-byte Folded Reload
; GCN: v_subrev_i32_e32 [[SUB:v[0-9]+]], vcc, v{{[0-9]+}}, v[[LOAD0_RELOAD]]
; GCN: buffer_store_dword [[ADD]], off, s[0:3], 0 offset:[[FLOW_RESULT_OFFSET:[0-9]+]] ; 4-byte Folded Spill
; GCN-NEXT: s_branch [[FLOW]]
; GCN: [[ENDIF]]:
; GCN: buffer_load_dword v[[RESULT:[0-9]+]], off, s[0:3], 0 offset:[[RESULT_OFFSET]] ; 4-byte Folded Reload
; VGPR: v_readlane_b32 s[[S_RELOAD_SAVEEXEC_LO:[0-9]+]], [[SPILL_VGPR]], [[FLOW_SAVEEXEC_LO_LANE]]
; VGPR: v_readlane_b32 s[[S_RELOAD_SAVEEXEC_HI:[0-9]+]], [[SPILL_VGPR]], [[FLOW_SAVEEXEC_HI_LANE]]
; VMEM: buffer_load_dword v[[V_RELOAD_SAVEEXEC:[0-9]+]], off, s[0:3], 0 offset:[[FLOW_SAVEEXEC_OFFSET]] ; 4-byte Folded Reload
; VMEM: s_waitcnt vmcnt(0)
; VMEM: v_readlane_b32 s[[S_RELOAD_SAVEEXEC_LO:[0-9]+]], v[[V_RELOAD_SAVEEXEC]], 0
; VMEM: v_readlane_b32 s[[S_RELOAD_SAVEEXEC_HI:[0-9]+]], v[[V_RELOAD_SAVEEXEC]], 1
; GCN: s_or_b64 exec, exec, s[[[S_RELOAD_SAVEEXEC_LO]]:[[S_RELOAD_SAVEEXEC_HI]]]
; GCN: flat_store_dword v{{\[[0-9]+:[0-9]+\]}}, v[[RESULT]]
define amdgpu_kernel void @divergent_if_else_endif(i32 addrspace(1)* %out) #0 {
entry:
%tid = call i32 @llvm.amdgcn.workitem.id.x()
%load0 = load volatile i32, i32 addrspace(3)* null
%cmp0 = icmp eq i32 %tid, 0
br i1 %cmp0, label %if, label %else
if:
%load1 = load volatile i32, i32 addrspace(3)* undef
%val0 = add i32 %load0, %load1
br label %endif
else:
%load2 = load volatile i32, i32 addrspace(3)* undef
%val1 = sub i32 %load0, %load2
br label %endif
endif:
%result = phi i32 [ %val0, %if ], [ %val1, %else ]
store i32 %result, i32 addrspace(1)* %out
ret void
}
declare i32 @llvm.amdgcn.workitem.id.x() #1
attributes #0 = { nounwind }
attributes #1 = { nounwind readnone }