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[LoongArch] Too many sp adjustment instructions in the prologue #88109

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heiher opened this issue Apr 9, 2024 · 0 comments · Fixed by #88110
Closed

[LoongArch] Too many sp adjustment instructions in the prologue #88109

heiher opened this issue Apr 9, 2024 · 0 comments · Fixed by #88110
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@heiher
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backend:loongarch missed-optimization

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@heiher
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heiher commented Apr 9, 2024

For this reproducer:

define void @large_frame_size() {
  %1 = alloca [16384 x { i32, i32 }], align 4
  ret void
}

There are too many instructions generated for sp adjustment in the prologue:

clang -target loongarch64 -S -o - large-frame-size.ll
	.text
	.file	"large-frame-size.ll"
	.globl	large_frame_size                # -- Begin function large_frame_size
	.p2align	5
	.type	large_frame_size,@function
large_frame_size:                       # @large_frame_size
	.cfi_startproc
# %bb.0:
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -2048
	addi.d	$sp, $sp, -16
	.cfi_def_cfa_offset 131088
	lu12i.w	$a0, 32
	ori	$a0, $a0, 16
	add.d	$sp, $sp, $a0
	ret
.Lfunc_end0:
	.size	large_frame_size, .Lfunc_end0-large_frame_size
	.cfi_endproc
                                        # -- End function
	.section	".note.GNU-stack","",@progbits
	.addrsig
@heiher heiher self-assigned this Apr 9, 2024
@heiher heiher mentioned this issue Apr 9, 2024
Merged
heiher added a commit to heiher/llvm-project that referenced this issue Apr 9, 2024
@heiher
[LoongArch] Revert sp adjustment in prologue
70cd1a8 
After commit 18c5f3c ("[RegisterScavenger][RISCV] Don't search for FrameSetup
instrs if we were searching from Non-FrameSetup instrs"), we can revert the `sp`
adjustment 4e2364a ("[LoongArch] Add emergency spill slot for GPR for large
frames") to generate better code, as the issue with `RegScavenger` has been
resolved.

Fixes llvm#88109
heiher added a commit that referenced this issue Apr 10, 2024
@heiher
[LoongArch] Revert sp adjustment in prologue (#88110)
0d17e1f 
After commit 18c5f3c ("[RegisterScavenger][RISCV] Don't search for
FrameSetup instrs if we were searching from Non-FrameSetup instrs"), we
can revert the `sp` adjustment 4e2364a ("[LoongArch] Add emergency
spill slot for GPR for large frames") to generate better code, as the
issue with `RegScavenger` has been resolved.

Fixes #88109
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[LoongArch] Revert sp adjustment in prologue heiher/llvm-project
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@heiher @EugeneZelenko