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[SDAG] Add missing ppc_fp128 ExpandFloatRes for sincos[pi] #128514

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Merged
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Feb 25, 2025
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[SDAG] Add missing ppc_fp128 ExpandFloatRes for sincos[pi] #128514

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[SDAG] Add missing ppc_fp128 ExpandFloatRes for sincos[pi]
MacDue Feb 24, 2025
093dd26
Add tail call test
MacDue Feb 24, 2025
652535f
Add other tail call form
MacDue Feb 24, 2025
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46 changes: 46 additions & 0 deletions llvm/test/CodeGen/PowerPC/llvm.sincos.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -49,3 +49,49 @@ define { ppc_fp128, ppc_fp128 } @test_sincospi_ppcf128(ppc_fp128 %a) {
%result = call { ppc_fp128, ppc_fp128 } @llvm.sincospi.ppcf128(ppc_fp128 %a)
ret { ppc_fp128, ppc_fp128 } %result
}

; FIXME: Recognise this as a tail call and omit the stack frame:
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@arsenm arsenm Feb 24, 2025

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I don't think this can be recognized as a tail call, the return needs to be the immediate next instruction after the call

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@MacDue MacDue Feb 24, 2025

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the return needs to be the immediate next instruction after the call

That is what codegen emits, the stores and extractvalues fold away to nothing, though the tail call logic does not recognise this.

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@arsenm arsenm Feb 24, 2025

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What do you mean by "what the codegen emits"? The issue is what is in the IR. This function should return the original { ppc_fp128, ppc_fp128 } with no extracts or stores

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@MacDue MacDue Feb 24, 2025 •
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Right, but returning a struct would never result in a tail call for the standard expansion.
This IR does result in something that codegen could recognise as a tail call (and there's logic in SDAG that could do this), but right now it fails to do so. Look at the current codegen:

; CHECK-LABEL: test_sincos_ppcf128_tail_call:
; CHECK:       # %bb.0:
<frame setup>
; CHECK-NEXT:    mflr r0
; CHECK-NEXT:    stdu r1, -32(r1)
; CHECK-NEXT:    std r0, 48(r1)
; CHECK-NEXT:    .cfi_def_cfa_offset 32
; CHECK-NEXT:    .cfi_offset lr, 16

<call to sincos>
; CHECK-NEXT:    bl sincosl

<frame destruction> 
; CHECK-NEXT:    nop
; CHECK-NEXT:    addi r1, r1, 32
; CHECK-NEXT:    ld r0, 16(r1)
; CHECK-NEXT:    mtlr r0
; CHECK-NEXT:    blr

This could simply be a jump to sincosl.

define void @test_sincos_ppcf128_tail_call(ppc_fp128 %a, ptr noalias %out_sin, ptr noalias %out_cos) {
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@arsenm arsenm Feb 24, 2025

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This should return the raw structure type

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@MacDue MacDue Feb 24, 2025

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That won't result in something that could be a tail call on any target that uses the (semi)-standard GNU sincos function (since it'll need to emit loads after the call).

; CHECK-LABEL: test_sincos_ppcf128_tail_call:
; CHECK: # %bb.0:
; CHECK-NEXT: mflr r0
; CHECK-NEXT: stdu r1, -32(r1)
; CHECK-NEXT: std r0, 48(r1)
; CHECK-NEXT: .cfi_def_cfa_offset 32
; CHECK-NEXT: .cfi_offset lr, 16
; CHECK-NEXT: bl sincosl
; CHECK-NEXT: nop
; CHECK-NEXT: addi r1, r1, 32
; CHECK-NEXT: ld r0, 16(r1)
; CHECK-NEXT: mtlr r0
; CHECK-NEXT: blr
%result = tail call { ppc_fp128, ppc_fp128 } @llvm.sincos.ppcf128(ppc_fp128 %a)
%result.0 = extractvalue { ppc_fp128, ppc_fp128 } %result, 0
%result.1 = extractvalue { ppc_fp128, ppc_fp128 } %result, 1
store ppc_fp128 %result.0, ptr %out_sin, align 16
store ppc_fp128 %result.1, ptr %out_cos, align 16
ret void
}

; FIXME: Recognise this as a tail call and omit the stack frame:
define void @test_sincospi_ppcf128_tail_call(ppc_fp128 %a, ptr noalias %out_sin, ptr noalias %out_cos) {
; CHECK-LABEL: test_sincospi_ppcf128_tail_call:
; CHECK: # %bb.0:
; CHECK-NEXT: mflr r0
; CHECK-NEXT: stdu r1, -32(r1)
; CHECK-NEXT: std r0, 48(r1)
; CHECK-NEXT: .cfi_def_cfa_offset 32
; CHECK-NEXT: .cfi_offset lr, 16
; CHECK-NEXT: bl sincospil
; CHECK-NEXT: nop
; CHECK-NEXT: addi r1, r1, 32
; CHECK-NEXT: ld r0, 16(r1)
; CHECK-NEXT: mtlr r0
; CHECK-NEXT: blr
%result = tail call { ppc_fp128, ppc_fp128 } @llvm.sincospi.ppcf128(ppc_fp128 %a)
%result.0 = extractvalue { ppc_fp128, ppc_fp128 } %result, 0
%result.1 = extractvalue { ppc_fp128, ppc_fp128 } %result, 1
store ppc_fp128 %result.0, ptr %out_sin, align 16
store ppc_fp128 %result.1, ptr %out_cos, align 16
ret void
}
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