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[SplitKit] Cope with no live subranges in defFromParent

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Following on from D87757 "[SplitKit] Only copy live lanes", it is
possible to split a live range at a point when none of its subranges
are live. This patch handles that case by inserting an implicit def
of the superreg.

Patch by Quentin Colombet!

Differential Revision: https://reviews.llvm.org/D88397
This commit is contained in:
Jay Foad 2020-09-28 09:30:58 +01:00
parent 810817f7d6
commit 60268b2488
2 changed files with 51 additions and 3 deletions
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12
lib/CodeGen/SplitKit.cpp
View File

@ -663,13 +663,19 @@ VNInfo *SplitEditor::defFromParent(unsigned RegIdx,
if (S.liveAt(UseIdx))
LaneMask |= S.LaneMask;
}
assert(LaneMask.any() && "Interval has no live subranges");
} else {
LaneMask = LaneBitmask::getAll();
}
++NumCopies;
Def = buildCopy(Edit->getReg(), Reg, LaneMask, MBB, I, Late, RegIdx);
if (LaneMask.none()) {
const MCInstrDesc &Desc = TII.get(TargetOpcode::IMPLICIT_DEF);
MachineInstr *ImplicitDef = BuildMI(MBB, I, DebugLoc(), Desc, Reg);
SlotIndexes &Indexes = *LIS.getSlotIndexes();
Def = Indexes.insertMachineInstrInMaps(*ImplicitDef, Late).getRegSlot();
} else {
++NumCopies;
Def = buildCopy(Edit->getReg(), Reg, LaneMask, MBB, I, Late, RegIdx);
}
}
// Define the value in Reg.

42
test/CodeGen/AMDGPU/splitkit-nolivesubranges.mir Normal file
View File

@ -0,0 +1,42 @@
# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
# RUN: llc -march=amdgcn -run-pass=greedy,virtregrewriter -verify-regalloc %s -o - | FileCheck %s
# This test aims to trigger live-range splitting at a place where %0 subranges
# are all dead, but the main live-range of %0 is still alive. %0 main range is
# kept alive simply by not using undef. Then, the splitting is triggered by
# creating two points of high register pressure:
# - One where %0 main range is the only live live-range: this will force the
# insertion of a split for %0 main range.
# - One where %0.subrange is live, so that the interference check in regalloc
# triggers the splitting heuristic.
---
name: func0
tracksRegLiveness: true
body: |
bb.0:
liveins: $sgpr0_sgpr1
; CHECK-LABEL: name: func0
; CHECK: liveins: $sgpr0_sgpr1
; CHECK: renamable $sgpr0 = IMPLICIT_DEF
; CHECK: renamable $sgpr1 = IMPLICIT_DEF
; CHECK: $sgpr104 = S_AND_B32 renamable $sgpr0, renamable $sgpr1, implicit-def $scc
; CHECK: KILL implicit-def $vcc, implicit-def $sgpr0_sgpr1_sgpr2_sgpr3_sgpr4_sgpr5_sgpr6_sgpr7_sgpr8_sgpr9_sgpr10_sgpr11_sgpr12_sgpr13_sgpr14_sgpr15_sgpr16_sgpr17_sgpr18_sgpr19_sgpr20_sgpr21_sgpr22_sgpr23_sgpr24_sgpr25_sgpr26_sgpr27_sgpr28_sgpr29_sgpr30_sgpr31, implicit-def $sgpr32_sgpr33_sgpr34_sgpr35_sgpr36_sgpr37_sgpr38_sgpr39_sgpr40_sgpr41_sgpr42_sgpr43_sgpr44_sgpr45_sgpr46_sgpr47_sgpr48_sgpr49_sgpr50_sgpr51_sgpr52_sgpr53_sgpr54_sgpr55_sgpr56_sgpr57_sgpr58_sgpr59_sgpr60_sgpr61_sgpr62_sgpr63, implicit-def $sgpr64_sgpr65_sgpr66_sgpr67_sgpr68_sgpr69_sgpr70_sgpr71_sgpr72_sgpr73_sgpr74_sgpr75_sgpr76_sgpr77_sgpr78_sgpr79_sgpr80_sgpr81_sgpr82_sgpr83_sgpr84_sgpr85_sgpr86_sgpr87_sgpr88_sgpr89_sgpr90_sgpr91_sgpr92_sgpr93_sgpr94_sgpr95, implicit-def $sgpr96_sgpr97_sgpr98_sgpr99_sgpr100_sgpr101_sgpr102_sgpr103
; CHECK: renamable $sgpr0_sgpr1 = IMPLICIT_DEF
; CHECK: renamable $sgpr0 = IMPLICIT_DEF
; CHECK: renamable $sgpr1 = IMPLICIT_DEF
; CHECK: SI_SPILL_S64_SAVE renamable $sgpr0_sgpr1, %stack.0, implicit $exec, implicit $private_rsrc_reg, implicit $sp_reg :: (store 8 into %stack.0, align 4, addrspace 5)
; CHECK: KILL implicit-def $vcc, implicit-def $sgpr0_sgpr1_sgpr2_sgpr3_sgpr4_sgpr5_sgpr6_sgpr7_sgpr8_sgpr9_sgpr10_sgpr11_sgpr12_sgpr13_sgpr14_sgpr15_sgpr16_sgpr17_sgpr18_sgpr19_sgpr20_sgpr21_sgpr22_sgpr23_sgpr24_sgpr25_sgpr26_sgpr27_sgpr28_sgpr29_sgpr30_sgpr31, implicit-def $sgpr32_sgpr33_sgpr34_sgpr35_sgpr36_sgpr37_sgpr38_sgpr39_sgpr40_sgpr41_sgpr42_sgpr43_sgpr44_sgpr45_sgpr46_sgpr47_sgpr48_sgpr49_sgpr50_sgpr51_sgpr52_sgpr53_sgpr54_sgpr55_sgpr56_sgpr57_sgpr58_sgpr59_sgpr60_sgpr61_sgpr62_sgpr63, implicit-def $sgpr64_sgpr65_sgpr66_sgpr67_sgpr68_sgpr69_sgpr70_sgpr71_sgpr72_sgpr73_sgpr74_sgpr75_sgpr76_sgpr77_sgpr78_sgpr79_sgpr80_sgpr81_sgpr82_sgpr83_sgpr84_sgpr85_sgpr86_sgpr87_sgpr88_sgpr89_sgpr90_sgpr91_sgpr92_sgpr93_sgpr94_sgpr95, implicit-def $sgpr96_sgpr97_sgpr98_sgpr99_sgpr100_sgpr101_sgpr102_sgpr103
; CHECK: renamable $sgpr0_sgpr1 = SI_SPILL_S64_RESTORE %stack.0, implicit $exec, implicit $private_rsrc_reg, implicit $sp_reg :: (load 8 from %stack.0, align 4, addrspace 5)
; CHECK: $sgpr105 = S_AND_B32 renamable $sgpr1, renamable $sgpr1, implicit-def $scc
; CHECK: S_NOP 0, implicit $sgpr104, implicit $sgpr105
%0:sreg_64 = COPY $sgpr0_sgpr1
%0.sub0:sreg_64 = IMPLICIT_DEF
%0.sub1:sreg_64 = IMPLICIT_DEF
$sgpr104 = S_AND_B32 %0.sub0, %0.sub1, implicit-def $scc
KILL implicit-def $vcc, implicit-def $sgpr0_sgpr1_sgpr2_sgpr3_sgpr4_sgpr5_sgpr6_sgpr7_sgpr8_sgpr9_sgpr10_sgpr11_sgpr12_sgpr13_sgpr14_sgpr15_sgpr16_sgpr17_sgpr18_sgpr19_sgpr20_sgpr21_sgpr22_sgpr23_sgpr24_sgpr25_sgpr26_sgpr27_sgpr28_sgpr29_sgpr30_sgpr31, implicit-def $sgpr32_sgpr33_sgpr34_sgpr35_sgpr36_sgpr37_sgpr38_sgpr39_sgpr40_sgpr41_sgpr42_sgpr43_sgpr44_sgpr45_sgpr46_sgpr47_sgpr48_sgpr49_sgpr50_sgpr51_sgpr52_sgpr53_sgpr54_sgpr55_sgpr56_sgpr57_sgpr58_sgpr59_sgpr60_sgpr61_sgpr62_sgpr63, implicit-def $sgpr64_sgpr65_sgpr66_sgpr67_sgpr68_sgpr69_sgpr70_sgpr71_sgpr72_sgpr73_sgpr74_sgpr75_sgpr76_sgpr77_sgpr78_sgpr79_sgpr80_sgpr81_sgpr82_sgpr83_sgpr84_sgpr85_sgpr86_sgpr87_sgpr88_sgpr89_sgpr90_sgpr91_sgpr92_sgpr93_sgpr94_sgpr95, implicit-def $sgpr96_sgpr97_sgpr98_sgpr99_sgpr100_sgpr101_sgpr102_sgpr103
%0.sub0:sreg_64 = IMPLICIT_DEF
%0.sub1:sreg_64 = IMPLICIT_DEF
KILL implicit-def $vcc, implicit-def $sgpr0_sgpr1_sgpr2_sgpr3_sgpr4_sgpr5_sgpr6_sgpr7_sgpr8_sgpr9_sgpr10_sgpr11_sgpr12_sgpr13_sgpr14_sgpr15_sgpr16_sgpr17_sgpr18_sgpr19_sgpr20_sgpr21_sgpr22_sgpr23_sgpr24_sgpr25_sgpr26_sgpr27_sgpr28_sgpr29_sgpr30_sgpr31, implicit-def $sgpr32_sgpr33_sgpr34_sgpr35_sgpr36_sgpr37_sgpr38_sgpr39_sgpr40_sgpr41_sgpr42_sgpr43_sgpr44_sgpr45_sgpr46_sgpr47_sgpr48_sgpr49_sgpr50_sgpr51_sgpr52_sgpr53_sgpr54_sgpr55_sgpr56_sgpr57_sgpr58_sgpr59_sgpr60_sgpr61_sgpr62_sgpr63, implicit-def $sgpr64_sgpr65_sgpr66_sgpr67_sgpr68_sgpr69_sgpr70_sgpr71_sgpr72_sgpr73_sgpr74_sgpr75_sgpr76_sgpr77_sgpr78_sgpr79_sgpr80_sgpr81_sgpr82_sgpr83_sgpr84_sgpr85_sgpr86_sgpr87_sgpr88_sgpr89_sgpr90_sgpr91_sgpr92_sgpr93_sgpr94_sgpr95, implicit-def $sgpr96_sgpr97_sgpr98_sgpr99_sgpr100_sgpr101_sgpr102_sgpr103
$sgpr105 = S_AND_B32 %0.sub1, %0.sub1, implicit-def $scc
S_NOP 0, implicit $sgpr104, implicit $sgpr105
...