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[StackSlotColoring] Ignore non-spill objects in RemoveDeadStores. #80242

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Feb 1, 2024
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[StackSlotColoring] Ignore non-spill objects in RemoveDeadStores. #80242

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19f1916
[RISCV] Add test case for PR80052. NFC
topperc Feb 1, 2024
739901b
[StackSlotColoring] Ignore non-spill objects in RemoveDeadStores.
topperc Feb 1, 2024
e42fccf
fixup! remove IR from test.
topperc Feb 1, 2024
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2 changes: 1 addition & 1 deletion llvm/lib/CodeGen/StackSlotColoring.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -480,7 +480,7 @@ bool StackSlotColoring::RemoveDeadStores(MachineBasicBlock* MBB) {
if (!(StoreReg = TII->isStoreToStackSlot(*NextMI, SecondSS, StoreSize)))
continue;
if (FirstSS != SecondSS || LoadReg != StoreReg || FirstSS == -1 ||
LoadSize != StoreSize)
LoadSize != StoreSize || !MFI->isSpillSlotObjectIndex(FirstSS))
continue;

++NumDead;
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116 changes: 116 additions & 0 deletions llvm/test/CodeGen/RISCV/pr80052.mir
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@@ -0,0 +1,116 @@
# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 4
# RUN: llc %s -mtriple=riscv64 -run-pass=greedy,virtregrewriter,stack-slot-coloring -o - | FileCheck %s

---
name: foo
alignment: 4
tracksRegLiveness: true
frameInfo:
maxAlignment: 4
localFrameSize: 4
stack:
- { id: 0, size: 1, alignment: 4, local-offset: -4 }
machineFunctionInfo:
varArgsFrameIndex: 0
varArgsSaveSize: 0
body: |
bb.0.entry:
; To trick stack-slot-colouring to run its dead-store-elimination phase,
; which is at fault, we need the register allocator to run, and spill in two
; places that can have their slots merged. Achieve this by volatile-loading
; data into all allocatable GPRs except $x31. Then, volatile storing them
; later, leaving regalloc only $x31 to play with in the middle.
$x1 = LW %stack.0, 0 :: (volatile load (s32))
$x5 = LW %stack.0, 0 :: (volatile load (s32))
$x6 = LW %stack.0, 0 :: (volatile load (s32))
$x7 = LW %stack.0, 0 :: (volatile load (s32))
$x8 = LW %stack.0, 0 :: (volatile load (s32))
$x9 = LW %stack.0, 0 :: (volatile load (s32))
$x10 = LW %stack.0, 0 :: (volatile load (s32))
$x11 = LW %stack.0, 0 :: (volatile load (s32))
$x12 = LW %stack.0, 0 :: (volatile load (s32))
$x13 = LW %stack.0, 0 :: (volatile load (s32))
$x14 = LW %stack.0, 0 :: (volatile load (s32))
$x15 = LW %stack.0, 0 :: (volatile load (s32))
$x16 = LW %stack.0, 0 :: (volatile load (s32))
$x17 = LW %stack.0, 0 :: (volatile load (s32))
$x18 = LW %stack.0, 0 :: (volatile load (s32))
$x19 = LW %stack.0, 0 :: (volatile load (s32))
$x20 = LW %stack.0, 0 :: (volatile load (s32))
$x21 = LW %stack.0, 0 :: (volatile load (s32))
$x22 = LW %stack.0, 0 :: (volatile load (s32))
$x23 = LW %stack.0, 0 :: (volatile load (s32))
$x24 = LW %stack.0, 0 :: (volatile load (s32))
$x25 = LW %stack.0, 0 :: (volatile load (s32))
$x26 = LW %stack.0, 0 :: (volatile load (s32))
$x27 = LW %stack.0, 0 :: (volatile load (s32))
$x28 = LW %stack.0, 0 :: (volatile load (s32))
$x29 = LW %stack.0, 0 :: (volatile load (s32))
$x30 = LW %stack.0, 0 :: (volatile load (s32))

; Force the first spill.
%0:gpr = LW %stack.0, 0 :: (volatile load (s32))
%1:gpr = LW %stack.0, 0 :: (volatile load (s32))
SW %1, %stack.0, 0 :: (volatile store (s32))
SW %0, %stack.0, 0 :: (volatile store (s32))

; CHECK: renamable $x31 = LW %stack.0, 0 :: (volatile load (s32))
; CHECK-NEXT: SD killed renamable $x31, %stack.1, 0 :: (store (s64) into %stack.1)
; CHECK-NEXT: renamable $x31 = LW %stack.0, 0 :: (volatile load (s32))
; CHECK-NEXT: SW killed renamable $x31, %stack.0, 0 :: (volatile store (s32))
; CHECK-NEXT: renamable $x31 = LD %stack.1, 0 :: (load (s64) from %stack.1)
; CHECK-NEXT: SW killed renamable $x31, %stack.0, 0 :: (volatile store (s32))

; stack-slot-coloring doesn't know that a write to $x0 is discarded.
dead $x0 = LW %stack.0, 0 :: (volatile load (s32))
; This stores 0 rather than the result of the preceding load since $x0
; is special.
; We don't want this store to be deleted.
SW $x0, %stack.0, 0 :: (volatile store (s32))

; CHECK-NEXT: dead $x0 = LW %stack.0, 0 :: (volatile load (s32))
; CHECK-NEXT: SW $x0, %stack.0, 0 :: (volatile store (s32))

; Force a second spill
%2:gpr = LW %stack.0, 0 :: (volatile load (s32))
%3:gpr = LW %stack.0, 0 :: (volatile load (s32))
SW %3, %stack.0, 0 :: (volatile store (s32))
SW %2, %stack.0, 0 :: (volatile store (s32))

; CHECK-NEXT: renamable $x31 = LW %stack.0, 0 :: (volatile load (s32))
; CHECK-NEXT: SD killed renamable $x31, %stack.1, 0 :: (store (s64) into %stack.1)
; CHECK-NEXT: renamable $x31 = LW %stack.0, 0 :: (volatile load (s32))
; CHECK-NEXT: SW killed renamable $x31, %stack.0, 0 :: (volatile store (s32))
; CHECK-NEXT: renamable $x31 = LD %stack.1, 0 :: (load (s64) from %stack.1)
; CHECK-NEXT: SW killed renamable $x31, %stack.0, 0 :: (volatile store (s32))

SW $x1, %stack.0, 0 :: (volatile store (s32))
SW $x5, %stack.0, 0 :: (volatile store (s32))
SW $x6, %stack.0, 0 :: (volatile store (s32))
SW $x7, %stack.0, 0 :: (volatile store (s32))
SW $x8, %stack.0, 0 :: (volatile store (s32))
SW $x9, %stack.0, 0 :: (volatile store (s32))
SW $x10, %stack.0, 0 :: (volatile store (s32))
SW $x11, %stack.0, 0 :: (volatile store (s32))
SW $x12, %stack.0, 0 :: (volatile store (s32))
SW $x13, %stack.0, 0 :: (volatile store (s32))
SW $x14, %stack.0, 0 :: (volatile store (s32))
SW $x15, %stack.0, 0 :: (volatile store (s32))
SW $x16, %stack.0, 0 :: (volatile store (s32))
SW $x17, %stack.0, 0 :: (volatile store (s32))
SW $x18, %stack.0, 0 :: (volatile store (s32))
SW $x19, %stack.0, 0 :: (volatile store (s32))
SW $x20, %stack.0, 0 :: (volatile store (s32))
SW $x21, %stack.0, 0 :: (volatile store (s32))
SW $x22, %stack.0, 0 :: (volatile store (s32))
SW $x23, %stack.0, 0 :: (volatile store (s32))
SW $x24, %stack.0, 0 :: (volatile store (s32))
SW $x25, %stack.0, 0 :: (volatile store (s32))
SW $x26, %stack.0, 0 :: (volatile store (s32))
SW $x27, %stack.0, 0 :: (volatile store (s32))
SW $x28, %stack.0, 0 :: (volatile store (s32))
SW $x29, %stack.0, 0 :: (volatile store (s32))
SW $x30, %stack.0, 0 :: (volatile store (s32))
PseudoRET

...
2 changes: 1 addition & 1 deletion llvm/test/CodeGen/X86/pr30821.mir
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Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,7 @@ stack:
- { id: 1, name: foxtrot, type: default, offset: 0, size: 16, alignment: 16,
stack-id: default, callee-saved-register: '', callee-saved-restored: true,
debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
- { id: 2, name: india, type: default, offset: 0, size: 16, alignment: 16,
- { id: 2, name: india, type: spill-slot, offset: 0, size: 16, alignment: 16,
stack-id: default, callee-saved-register: '', callee-saved-restored: true,
debug-info-variable: '', debug-info-expression: '',
debug-info-location: '' }
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