Files
clang-p2996/llvm/test/CodeGen/AMDGPU/spill-empty-live-interval.mir
Scott Linder 60b1967c39 [AMDGPU] Add Scratch Wave Offset to Scratch Buffer Descriptor in entry functions
Add the scratch wave offset to the scratch buffer descriptor (SRSrc) in
the entry function prologue. This allows us to removes the scratch wave
offset register from the calling convention ABI.

As part of this change, allow the use of an inline constant zero for the
SOffset of MUBUF instructions accessing the stack in entry functions
when a frame pointer is not requested/required. Entry functions with
calls still need to set up the calling convention ABI stack pointer
register, and reference it in order to address arguments of called
functions. The ABI stack pointer register remains unswizzled, but is now
wave-relative instead of queue-relative.

Non-entry functions also use an inline constant zero SOffset for
wave-relative scratch access, but continue to use the stack and frame
pointers as before. When the stack or frame pointer is converted to a
swizzled offset it is now scaled directly, as the scratch wave offset no
longer needs to be subtracted first.

Update llvm/docs/AMDGPUUsage.rst to reflect these changes to the calling
convention.

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75138
2020-03-19 15:35:16 -04:00

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# RUN: llc -mtriple=amdgcn-amd-amdhsa -amdgpu-dce-in-ra=0 -verify-machineinstrs -stress-regalloc=1 -start-before=simple-register-coalescing -stop-after=greedy -o - %s | FileCheck %s
# https://bugs.llvm.org/show_bug.cgi?id=33620
---
# This would assert due to the empty live interval created for %9
# on the last S_NOP with an undef subreg use.
# CHECK-LABEL: name: expecting_non_empty_interval
# CHECK: undef %7.sub1:vreg_64 = V_MAC_F32_e32 0, undef %1:vgpr_32, undef %7.sub1, implicit $exec
# CHECK-NEXT: SI_SPILL_V64_SAVE %7, %stack.0, $sgpr0_sgpr1_sgpr2_sgpr3, $sgpr32, 0, implicit $exec :: (store 8 into %stack.0, align 4, addrspace 5)
# CHECK-NEXT: undef %5.sub1:vreg_64 = V_MOV_B32_e32 1786773504, implicit $exec
# CHECK-NEXT: dead %3:vgpr_32 = V_MUL_F32_e32 0, %5.sub1, implicit $exec
# CHECK: S_NOP 0, implicit %6.sub1
# CHECK-NEXT: %8:vreg_64 = SI_SPILL_V64_RESTORE %stack.0, $sgpr0_sgpr1_sgpr2_sgpr3, $sgpr32, 0, implicit $exec :: (load 8 from %stack.0, align 4, addrspace 5)
# CHECK-NEXT: S_NOP 0, implicit %8.sub1
# CHECK-NEXT: S_NOP 0, implicit undef %9.sub0
name: expecting_non_empty_interval
tracksRegLiveness: true
machineFunctionInfo:
scratchRSrcReg: $sgpr0_sgpr1_sgpr2_sgpr3
stackPtrOffsetReg: $sgpr32
body: |
bb.0:
successors: %bb.1
undef %0.sub1:vreg_64 = V_MAC_F32_e32 0, undef %1:vgpr_32, undef %0.sub1, implicit $exec
undef %2.sub1:vreg_64 = V_MOV_B32_e32 1786773504, implicit $exec
dead %3:vgpr_32 = V_MUL_F32_e32 0, %2.sub1, implicit $exec
bb.1:
S_NOP 0, implicit %2.sub1
S_NOP 0, implicit %0.sub1
S_NOP 0, implicit undef %0.sub0
...
# Similar assert which happens when trying to rematerialize.
# https://bugs.llvm.org/show_bug.cgi?id=33884
---
# CHECK-LABEL: name: rematerialize_empty_interval_has_reference
# CHECK-NOT: MOV
# CHECK: undef %1.sub2:vreg_128 = V_MOV_B32_e32 1786773504, implicit $exec
# CHECK: bb.1:
# CHECK-NEXT: S_NOP 0, implicit %1.sub2
# CHECK-NEXT: S_NOP 0, implicit undef %4.sub0
# CHECK-NEXT: undef %2.sub2:vreg_128 = V_MOV_B32_e32 0, implicit $exec
# CHECK-NEXT: S_NOP 0, implicit %2.sub2
name: rematerialize_empty_interval_has_reference
tracksRegLiveness: true
machineFunctionInfo:
scratchRSrcReg: $sgpr0_sgpr1_sgpr2_sgpr3
stackPtrOffsetReg: $sgpr32
body: |
bb.0:
successors: %bb.1
undef %0.sub2:vreg_128 = V_MOV_B32_e32 0, implicit $exec
undef %1.sub2:vreg_128 = V_MOV_B32_e32 1786773504, implicit $exec
bb.1:
S_NOP 0, implicit %1.sub2
S_NOP 0, implicit undef %0.sub0
S_NOP 0, implicit %0.sub2
...