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llvm-mirror/test/CodeGen/AArch64/fadd-combines.ll
Sanjay Patel 9bc8c780ab [DAGCombiner] tighten fast-math constraints for fma fold 
fadd (fma A, B, (fmul C, D)), E --> fma A, B, (fma C, D, E)

This is only allowed when "reassoc" is present on the fadd.

As discussed in D80801, this transform goes beyond
what is allowed by "contract" FMF (-ffp-contract=fast).
That is because we are fusing the trailing add of 'E' with a
multiply, but without "reassoc", the code mandates that the
products A*B and C*D are added together before adding in 'E'.

I've added this example to the LangRef to try to clarify the
meaning of "contract". If that seems reasonable, we should
probably do something similar for the clang docs because
there does not appear to be any formal spec for the behavior
of -ffp-contract=fast.

Differential Revision: https://reviews.llvm.org/D82499
2020-07-12 08:51:49 -04:00

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; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -mtriple=aarch64-none-linux-gnu -verify-machineinstrs | FileCheck %s
define double @test1(double %a, double %b) {
; CHECK-LABEL: test1:
; CHECK: // %bb.0:
; CHECK-NEXT: fadd d1, d1, d1
; CHECK-NEXT: fsub d0, d0, d1
; CHECK-NEXT: ret
%mul = fmul double %b, -2.000000e+00
%add1 = fadd double %a, %mul
ret double %add1
}
; DAGCombine will canonicalize 'a - 2.0*b' to 'a + -2.0*b'
define double @test2(double %a, double %b) {
; CHECK-LABEL: test2:
; CHECK: // %bb.0:
; CHECK-NEXT: fadd d1, d1, d1
; CHECK-NEXT: fsub d0, d0, d1
; CHECK-NEXT: ret
%mul = fmul double %b, 2.000000e+00
%add1 = fsub double %a, %mul
ret double %add1
}
define double @test3(double %a, double %b, double %c) {
; CHECK-LABEL: test3:
; CHECK: // %bb.0:
; CHECK-NEXT: fmul d0, d0, d1
; CHECK-NEXT: fadd d1, d2, d2
; CHECK-NEXT: fsub d0, d0, d1
; CHECK-NEXT: ret
%mul = fmul double %a, %b
%mul1 = fmul double %c, 2.000000e+00
%sub = fsub double %mul, %mul1
ret double %sub
}
define double @test4(double %a, double %b, double %c) {
; CHECK-LABEL: test4:
; CHECK: // %bb.0:
; CHECK-NEXT: fmul d0, d0, d1
; CHECK-NEXT: fadd d1, d2, d2
; CHECK-NEXT: fsub d0, d0, d1
; CHECK-NEXT: ret
%mul = fmul double %a, %b
%mul1 = fmul double %c, -2.000000e+00
%add2 = fadd double %mul, %mul1
ret double %add2
}
define <4 x float> @fmulnegtwo_vec(<4 x float> %a, <4 x float> %b) {
; CHECK-LABEL: fmulnegtwo_vec:
; CHECK: // %bb.0:
; CHECK-NEXT: fadd v1.4s, v1.4s, v1.4s
; CHECK-NEXT: fsub v0.4s, v0.4s, v1.4s
; CHECK-NEXT: ret
%mul = fmul <4 x float> %b, <float -2.0, float -2.0, float -2.0, float -2.0>
%add = fadd <4 x float> %a, %mul
ret <4 x float> %add
}
define <4 x float> @fmulnegtwo_vec_commute(<4 x float> %a, <4 x float> %b) {
; CHECK-LABEL: fmulnegtwo_vec_commute:
; CHECK: // %bb.0:
; CHECK-NEXT: fadd v1.4s, v1.4s, v1.4s
; CHECK-NEXT: fsub v0.4s, v0.4s, v1.4s
; CHECK-NEXT: ret
%mul = fmul <4 x float> %b, <float -2.0, float -2.0, float -2.0, float -2.0>
%add = fadd <4 x float> %mul, %a
ret <4 x float> %add
}
define <4 x float> @fmulnegtwo_vec_undefs(<4 x float> %a, <4 x float> %b) {
; CHECK-LABEL: fmulnegtwo_vec_undefs:
; CHECK: // %bb.0:
; CHECK-NEXT: fadd v1.4s, v1.4s, v1.4s
; CHECK-NEXT: fsub v0.4s, v0.4s, v1.4s
; CHECK-NEXT: ret
%mul = fmul <4 x float> %b, <float undef, float -2.0, float undef, float -2.0>
%add = fadd <4 x float> %a, %mul
ret <4 x float> %add
}
define <4 x float> @fmulnegtwo_vec_commute_undefs(<4 x float> %a, <4 x float> %b) {
; CHECK-LABEL: fmulnegtwo_vec_commute_undefs:
; CHECK: // %bb.0:
; CHECK-NEXT: fadd v1.4s, v1.4s, v1.4s
; CHECK-NEXT: fsub v0.4s, v0.4s, v1.4s
; CHECK-NEXT: ret
%mul = fmul <4 x float> %b, <float -2.0, float undef, float -2.0, float -2.0>
%add = fadd <4 x float> %mul, %a
ret <4 x float> %add
}
define <4 x float> @test6(<4 x float> %a, <4 x float> %b) {
; CHECK-LABEL: test6:
; CHECK: // %bb.0:
; CHECK-NEXT: fadd v1.4s, v1.4s, v1.4s
; CHECK-NEXT: fsub v0.4s, v0.4s, v1.4s
; CHECK-NEXT: ret
%mul = fmul <4 x float> %b, <float 2.0, float 2.0, float 2.0, float 2.0>
%add = fsub <4 x float> %a, %mul
ret <4 x float> %add
}
; Don't fold (fadd A, (fmul B, -2.0)) -> (fsub A, (fadd B, B)) if the fmul has
; multiple uses.
define double @test7(double %a, double %b) nounwind {
; CHECK-LABEL: test7:
; CHECK: // %bb.0:
; CHECK-NEXT: str d8, [sp, #-16]! // 8-byte Folded Spill
; CHECK-NEXT: fmov d2, #-2.00000000
; CHECK-NEXT: fmul d1, d1, d2
; CHECK-NEXT: fadd d8, d0, d1
; CHECK-NEXT: mov v0.16b, v1.16b
; CHECK-NEXT: str x30, [sp, #8] // 8-byte Folded Spill
; CHECK-NEXT: bl use
; CHECK-NEXT: ldr x30, [sp, #8] // 8-byte Folded Reload
; CHECK-NEXT: mov v0.16b, v8.16b
; CHECK-NEXT: ldr d8, [sp], #16 // 8-byte Folded Reload
; CHECK-NEXT: ret
%mul = fmul double %b, -2.000000e+00
%add1 = fadd double %a, %mul
call void @use(double %mul)
ret double %add1
}
define float @fadd_const_multiuse_fmf(float %x) {
; CHECK-LABEL: fadd_const_multiuse_fmf:
; CHECK: // %bb.0:
; CHECK-DAG: mov [[W59:w[0-9]+]], #1114374144
; CHECK-DAG: mov [[W42:w[0-9]+]], #1109917696
; CHECK-DAG: fmov [[FP59:s[0-9]+]], [[W59]]
; CHECK-DAG: fmov [[FP42:s[0-9]+]], [[W42]]
; CHECK-NEXT: fadd [[TMP1:s[0-9]+]], s0, [[FP42]]
; CHECK-NEXT: fadd [[TMP2:s[0-9]+]], s0, [[FP59]]
; CHECK-NEXT: fadd s0, [[TMP1]], [[TMP2]]
; CHECK-NEXT: ret
%a1 = fadd float %x, 42.0
%a2 = fadd nsz reassoc float %a1, 17.0
%a3 = fadd float %a1, %a2
ret float %a3
}
; DAGCombiner transforms this into: (x + 17.0) + (x + 59.0).
define float @fadd_const_multiuse_attr(float %x) {
; CHECK-LABEL: fadd_const_multiuse_attr:
; CHECK: // %bb.0:
; CHECK-DAG: mov [[W17:w[0-9]+]], #1109917696
; CHECK-DAG: mov [[W59:w[0-9]+]], #1114374144
; CHECK-NEXT: fmov [[FP17:s[0-9]+]], [[W17]]
; CHECK-NEXT: fmov [[FP59:s[0-9]+]], [[W59]]
; CHECK-NEXT: fadd [[TMP1:s[0-9]+]], s0, [[FP17]]
; CHECK-NEXT: fadd [[TMP2:s[0-9]+]], s0, [[FP59]]
; CHECK-NEXT: fadd s0, [[TMP1]], [[TMP2]]
; CHECK-NEXT: ret
%a1 = fadd fast float %x, 42.0
%a2 = fadd fast float %a1, 17.0
%a3 = fadd fast float %a1, %a2
ret float %a3
}
; PR32939 - https://bugs.llvm.org/show_bug.cgi?id=32939
define double @fmul2_negated(double %a, double %b, double %c) {
; CHECK-LABEL: fmul2_negated:
; CHECK: // %bb.0:
; CHECK-NEXT: fadd d1, d1, d1
; CHECK-NEXT: fmul d1, d1, d2
; CHECK-NEXT: fsub d0, d0, d1
; CHECK-NEXT: ret
%mul = fmul double %b, 2.0
%mul1 = fmul double %mul, %c
%sub = fsub double %a, %mul1
ret double %sub
}
define <2 x double> @fmul2_negated_vec(<2 x double> %a, <2 x double> %b, <2 x double> %c) {
; CHECK-LABEL: fmul2_negated_vec:
; CHECK: // %bb.0:
; CHECK-NEXT: fadd v1.2d, v1.2d, v1.2d
; CHECK-NEXT: fmul v1.2d, v1.2d, v2.2d
; CHECK-NEXT: fsub v0.2d, v0.2d, v1.2d
; CHECK-NEXT: ret
%mul = fmul <2 x double> %b, <double 2.0, double 2.0>
%mul1 = fmul <2 x double> %mul, %c
%sub = fsub <2 x double> %a, %mul1
ret <2 x double> %sub
}
; ((a*b) + (c*d)) + n1 --> (a*b) + ((c*d) + n1)
define double @fadd_fma_fmul_1(double %a, double %b, double %c, double %d, double %n1) nounwind {
; CHECK-LABEL: fadd_fma_fmul_1:
; CHECK: // %bb.0:
; CHECK-NEXT: fmadd d2, d2, d3, d4
; CHECK-NEXT: fmadd d0, d0, d1, d2
; CHECK-NEXT: ret
%m1 = fmul fast double %a, %b
%m2 = fmul fast double %c, %d
%a1 = fadd fast double %m1, %m2
%a2 = fadd fast double %a1, %n1
ret double %a2
}
; Minimum FMF - the 1st fadd is contracted because that combines
; fmul+fadd as specified by the order of operations; the 2nd fadd
; requires reassociation to fuse with c*d.
define float @fadd_fma_fmul_fmf(float %a, float %b, float %c, float %d, float %n0) nounwind {
; CHECK-LABEL: fadd_fma_fmul_fmf:
; CHECK: // %bb.0:
; CHECK-NEXT: fmadd s2, s2, s3, s4
; CHECK-NEXT: fmadd s0, s0, s1, s2
; CHECK-NEXT: ret
%m1 = fmul float %a, %b
%m2 = fmul float %c, %d
%a1 = fadd contract float %m1, %m2
%a2 = fadd reassoc float %n0, %a1
ret float %a2
}
; Not minimum FMF.
define float @fadd_fma_fmul_2(float %a, float %b, float %c, float %d, float %n0) nounwind {
; CHECK-LABEL: fadd_fma_fmul_2:
; CHECK: // %bb.0:
; CHECK-NEXT: fmul s2, s2, s3
; CHECK-NEXT: fmadd s0, s0, s1, s2
; CHECK-NEXT: fadd s0, s4, s0
; CHECK-NEXT: ret
%m1 = fmul float %a, %b
%m2 = fmul float %c, %d
%a1 = fadd contract float %m1, %m2
%a2 = fadd contract float %n0, %a1
ret float %a2
}
; The final fadd can be folded with either 1 of the leading fmuls.
define <2 x double> @fadd_fma_fmul_3(<2 x double> %x1, <2 x double> %x2, <2 x double> %x3, <2 x double> %x4, <2 x double> %x5, <2 x double> %x6, <2 x double> %x7, <2 x double> %x8) nounwind {
; CHECK-LABEL: fadd_fma_fmul_3:
; CHECK: // %bb.0:
; CHECK-NEXT: fmul v2.2d, v2.2d, v3.2d
; CHECK-NEXT: fmla v2.2d, v1.2d, v0.2d
; CHECK-NEXT: fmla v2.2d, v7.2d, v6.2d
; CHECK-NEXT: fmla v2.2d, v5.2d, v4.2d
; CHECK-NEXT: mov v0.16b, v2.16b
; CHECK-NEXT: ret
%m1 = fmul fast <2 x double> %x1, %x2
%m2 = fmul fast <2 x double> %x3, %x4
%m3 = fmul fast <2 x double> %x5, %x6
%m4 = fmul fast <2 x double> %x7, %x8
%a1 = fadd fast <2 x double> %m1, %m2
%a2 = fadd fast <2 x double> %m3, %m4
%a3 = fadd fast <2 x double> %a1, %a2
ret <2 x double> %a3
}
; negative test
define float @fadd_fma_fmul_extra_use_1(float %a, float %b, float %c, float %d, float %n0, float* %p) nounwind {
; CHECK-LABEL: fadd_fma_fmul_extra_use_1:
; CHECK: // %bb.0:
; CHECK-NEXT: fmul s1, s0, s1
; CHECK-NEXT: fmadd s0, s2, s3, s1
; CHECK-NEXT: fadd s0, s4, s0
; CHECK-NEXT: str s1, [x0]
; CHECK-NEXT: ret
%m1 = fmul fast float %a, %b
store float %m1, float* %p
%m2 = fmul fast float %c, %d
%a1 = fadd fast float %m1, %m2
%a2 = fadd fast float %n0, %a1
ret float %a2
}
; negative test
define float @fadd_fma_fmul_extra_use_2(float %a, float %b, float %c, float %d, float %n0, float* %p) nounwind {
; CHECK-LABEL: fadd_fma_fmul_extra_use_2:
; CHECK: // %bb.0:
; CHECK-NEXT: fmul s2, s2, s3
; CHECK-NEXT: fmadd s0, s0, s1, s2
; CHECK-NEXT: fadd s0, s4, s0
; CHECK-NEXT: str s2, [x0]
; CHECK-NEXT: ret
%m1 = fmul fast float %a, %b
%m2 = fmul fast float %c, %d
store float %m2, float* %p
%a1 = fadd fast float %m1, %m2
%a2 = fadd fast float %n0, %a1
ret float %a2
}
; negative test
define float @fadd_fma_fmul_extra_use_3(float %a, float %b, float %c, float %d, float %n0, float* %p) nounwind {
; CHECK-LABEL: fadd_fma_fmul_extra_use_3:
; CHECK: // %bb.0:
; CHECK-NEXT: fmul s2, s2, s3
; CHECK-NEXT: fmadd s1, s0, s1, s2
; CHECK-NEXT: fadd s0, s4, s1
; CHECK-NEXT: str s1, [x0]
; CHECK-NEXT: ret
%m1 = fmul fast float %a, %b
%m2 = fmul fast float %c, %d
%a1 = fadd fast float %m1, %m2
store float %a1, float* %p
%a2 = fadd fast float %n0, %a1
ret float %a2
}
declare void @use(double)
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