5cf0fb4317
The stack slot coloring pass is concerned with optimizing spill
slots. If any change is a pass is made over the function to remove
stack stores that use the same register and stack slot as an
immediately preceding load.
The register check is too simple for constant registers like AArch64
and RISC-V's zero register. This register can be used as the result
of a load if we want to discard the result, but still have the memory
access performed. Like for a volatile or atomic load.
If the code sees a load from the zero register followed by a store
of the zero register at the same stack slot, the pass mistakenly
believes the store isn't needed.
Since the main stack coloring optimization is only concerned with
spill slots, it seems reasonable that RemoveDeadStores should
only be concerned with spills. Since we never generate a reload of
x0, this avoids the issue seen by RISC-V.
Test case concept is adapted from pr30821.mir from X86. That test
had to be updated to mark the stack slot as a spill slot.
Fixes #80052.
203 lines
12 KiB
YAML
203 lines
12 KiB
YAML
# RUN: llc -x mir < %s -run-pass=greedy,virtregrewriter,stack-slot-coloring | FileCheck %s
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--- |
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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define dso_local i32 @main() local_unnamed_addr {
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entry:
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; Dummy IR that just performs some allocas -- the machine IR function
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; below is what this test is about.
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%alpha = alloca i8, align 1
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%foxtrot = alloca <2 x double>, align 16
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%india = alloca <2 x double>, align 16
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ret i32 0
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}
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...
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---
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name: main
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alignment: 16
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exposesReturnsTwice: false
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legalized: false
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regBankSelected: false
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selected: false
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failedISel: false
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tracksRegLiveness: true
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registers:
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liveins:
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frameInfo:
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isFrameAddressTaken: false
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isReturnAddressTaken: false
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hasStackMap: false
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hasPatchPoint: false
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stackSize: 0
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offsetAdjustment: 0
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maxAlignment: 16
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adjustsStack: false
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hasCalls: true
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stackProtector: ''
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maxCallFrameSize: 4294967295
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hasOpaqueSPAdjustment: false
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hasVAStart: false
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hasMustTailInVarArgFunc: false
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localFrameSize: 0
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savePoint: ''
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restorePoint: ''
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fixedStack:
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stack:
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- { id: 0, name: alpha, type: default, offset: 0, size: 1, alignment: 1,
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stack-id: default, callee-saved-register: '', callee-saved-restored: true,
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debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
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- { id: 1, name: foxtrot, type: default, offset: 0, size: 16, alignment: 16,
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stack-id: default, callee-saved-register: '', callee-saved-restored: true,
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debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
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- { id: 2, name: india, type: spill-slot, offset: 0, size: 16, alignment: 16,
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stack-id: default, callee-saved-register: '', callee-saved-restored: true,
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debug-info-variable: '', debug-info-expression: '',
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debug-info-location: '' }
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constants:
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body: |
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bb.0.entry:
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; To trick stack-slot-colouring to run its dead-store-elimination phase,
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; which is at fault, we need the register allocator to run, and spill in two
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; places that can have their slots merged. Achieve this by volatile-loading
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; data into $xmm[0-14] and volatile storing them later, leaving regalloc only
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; $xmm15 to play with in the middle.
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; Then, perform two virtreg load-and-store pairs, with the faulty code
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; sequence in the middle (MOVSDrm then MOVAPDmr on the same slot). The
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; virtreg gets spilt; the corresponding stack slots merged; and faulty code
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; sequence eliminated if LLVM is broken.
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; Make first 15 $xmm registers live
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$xmm0 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm1 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm2 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm3 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm4 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm5 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm6 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm7 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm8 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm9 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm10 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm11 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm12 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm13 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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$xmm14 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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; First vreg load
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%1:vr128 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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; First faulty sequence; %1 spilt
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%12:fr64 = MOVSDrm_alt %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s64) from %ir.india)
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%13:vr128 = COPY killed %12
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MOVAPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed %13 :: (volatile store (s128) into %ir.india)
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; CHECK: renamable $xmm{{[0-9]+}} = MOVSDrm_alt %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s64) from %ir.india)
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; CHECK-NEXT: MOVAPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed renamable $xmm{{[0-9]+}} :: (volatile store (s128) into %ir.india)
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; Store %1 to avoid it being optimised out, will result in a load-from-spill
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed %1 :: (volatile dereferenceable store (s128) into %ir.india)
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; That code sequence a second time, to generate a second spill slot that
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; will get coloured and merged.
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%2:vr128 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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%22:fr64 = MOVSDrm_alt %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s64) from %ir.india)
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%23:vr128 = COPY killed %22
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MOVAPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed %23 :: (volatile store (s128) into %ir.india)
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; CHECK: renamable $xmm{{[0-9]+}} = MOVSDrm_alt %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s64) from %ir.india)
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; CHECK-NEXT: MOVAPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed renamable $xmm{{[0-9]+}} :: (volatile store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed %2 :: (volatile dereferenceable store (s128) into %ir.india)
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; Test some sequences that _should_ be eliminated
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%3:vr128 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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%32:fr64 = VMOVSDrm_alt %stack.2.india, 1, $noreg, 0, $noreg :: (dereferenceable load (s64) from %ir.india)
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%33:fr64 = COPY killed %32
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VMOVSDmr %stack.2.india, 1, $noreg, 0, $noreg, killed %33 :: (store (s64) into %ir.india)
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; This is the spill introduced by regalloc; we check that the inner dead
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; store and load were eliminated
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; CHECK: MOVAPSmr %stack.3, 1, $noreg, 0, $noreg, killed renamable $xmm{{[0-9]+}} :: (store (s128) into %stack.3)
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; CHECK-NEXT:renamable $xmm{{[0-9]+}} = MOVAPSrm %stack.3, 1, $noreg, 0, $noreg :: (load (s128) from %stack.3)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed %3 :: (volatile dereferenceable store (s128) into %ir.india)
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; Moves with different encodings but same size should be eliminated
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%4:vr128 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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%42:fr32 = MOVSSrm_alt %stack.2.india, 1, $noreg, 0, $noreg :: (dereferenceable load (s32) from %ir.india)
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%43:fr32 = COPY killed %42
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VMOVSSZmr %stack.2.india, 1, $noreg, 0, $noreg, killed %43 :: (store (s32) into %ir.india)
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; CHECK: MOVAPSmr %stack.3, 1, $noreg, 0, $noreg, killed renamable $xmm{{[0-9]+}} :: (store (s128) into %stack.3)
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; CHECK-NEXT:renamable $xmm{{[0-9]+}} = MOVAPSrm %stack.3, 1, $noreg, 0, $noreg :: (load (s128) from %stack.3)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed %4 :: (volatile dereferenceable store (s128) into %ir.india)
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; Same deal with double-size
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%5:vr128 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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%52:fr64 = MOVSDrm_alt %stack.2.india, 1, $noreg, 0, $noreg :: (dereferenceable load (s64) from %ir.india)
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%53:fr64 = COPY killed %52
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VMOVSDZmr %stack.2.india, 1, $noreg, 0, $noreg, killed %53 :: (store (s64) into %ir.india)
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; CHECK: MOVAPSmr %stack.3, 1, $noreg, 0, $noreg, killed renamable $xmm{{[0-9]+}} :: (store (s128) into %stack.3)
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; CHECK-NEXT:renamable $xmm{{[0-9]+}} = MOVAPSrm %stack.3, 1, $noreg, 0, $noreg :: (load (s128) from %stack.3)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed %5 :: (volatile dereferenceable store (s128) into %ir.india)
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; Last two repeated, with load/store opcode flipped
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%6:vr128 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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%62:fr32 = VMOVSSZrm_alt %stack.2.india, 1, $noreg, 0, $noreg :: (dereferenceable load (s32) from %ir.india)
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%63:fr32 = COPY killed %62
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MOVSSmr %stack.2.india, 1, $noreg, 0, $noreg, killed %63 :: (store (s32) into %ir.india)
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; CHECK: MOVAPSmr %stack.3, 1, $noreg, 0, $noreg, killed renamable $xmm{{[0-9]+}} :: (store (s128) into %stack.3)
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; CHECK-NEXT:renamable $xmm{{[0-9]+}} = MOVAPSrm %stack.3, 1, $noreg, 0, $noreg :: (load (s128) from %stack.3)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed %6 :: (volatile dereferenceable store (s128) into %ir.india)
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; Flipped double-size different-encoding test
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%7:vr128 = MOVUPDrm %stack.2.india, 1, $noreg, 0, $noreg :: (volatile dereferenceable load (s128) from %ir.india)
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%72:fr64 = VMOVSDZrm_alt %stack.2.india, 1, $noreg, 0, $noreg :: (dereferenceable load (s64) from %ir.india)
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%73:fr64 = COPY killed %72
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MOVSDmr %stack.2.india, 1, $noreg, 0, $noreg, killed %73 :: (store (s64) into %ir.india)
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; CHECK: MOVAPSmr %stack.3, 1, $noreg, 0, $noreg, killed renamable $xmm{{[0-9]+}} :: (store (s128) into %stack.3)
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; CHECK-NEXT:renamable $xmm{{[0-9]+}} = MOVAPSrm %stack.3, 1, $noreg, 0, $noreg :: (load (s128) from %stack.3)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed %7 :: (volatile dereferenceable store (s128) into %ir.india)
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; Stores of first 15 $xmm registers to keep them live across the middle of
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; this bb.
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm0 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm1 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm2 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm3 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm4 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm5 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm6 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm7 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm8 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm9 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm10 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm11 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm12 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm13 :: (volatile dereferenceable store (s128) into %ir.india)
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MOVUPDmr %stack.2.india, 1, $noreg, 0, $noreg, killed $xmm14 :: (volatile dereferenceable store (s128) into %ir.india)
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RET 0
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...
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