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Improve the precision of ARM64 S/CNRM2 by summing in double precision #5597

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Merged
martin-frbg merged 1 commit into from
Jan 11, 2026
Merged

Improve the precision of ARM64 S/CNRM2 by summing in double precision #5597

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47 changes: 10 additions & 37 deletions kernel/arm64/nrm2.S
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Original file line number Diff line number Diff line change
Expand Up @@ -35,16 +35,13 @@ USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#define I x3

#if !defined(DOUBLE)
#define SSQ s0
#define SCALE s1
#define REGZERO s5
#define REGONE s6
#else
#define SSQF s0
#endif

#define SSQ d0
#define SCALE d1
#define REGZERO d5
#define REGONE d6
#endif

/*******************************************************************************
* Macro definitions
Expand All @@ -53,22 +50,10 @@ USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.macro KERNEL_F1
#if !defined(DOUBLE)
ldr s4, [X], #4
fcmp s4, REGZERO
beq 2f /* KERNEL_F1_NEXT_\@ */
fabs s4, s4
fcmp SCALE, s4
bge 1f /* KERNEL_F1_SCALE_GE_X_\@ */
fdiv s2, SCALE, s4
fmul s2, s2, s2
fmul s3, SSQ, s2
fadd SSQ, REGONE, s3
fmov SCALE, s4
b 2f /* KERNEL_F1_NEXT_\@ */
1: /* KERNEL_F1_SCALE_GE_X_\@: */
fdiv s2, s4, SCALE
fmla SSQ, s2, v2.s[0]
fcvt d4, s4
#else
ldr d4, [X], #8
#endif
fcmp d4, REGZERO
beq 2f /* KERNEL_F1_NEXT_\@ */
fabs d4, d4
Expand All @@ -83,29 +68,16 @@ USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1: /* KERNEL_F1_SCALE_GE_X_\@: */
fdiv d2, d4, SCALE
fmla SSQ, d2, v2.d[0]
#endif
2: /* KERNEL_F1_NEXT_\@: */
.endm

.macro KERNEL_S1
#if !defined(DOUBLE)
ldr s4, [X]
fcmp s4, REGZERO
beq KERNEL_S1_NEXT
fabs s4, s4
fcmp SCALE, s4
bge KERNEL_S1_SCALE_GE_X
fdiv s2, SCALE, s4
fmul s2, s2, s2
fmul s3, SSQ, s2
fadd SSQ, REGONE, s3
fmov SCALE, s4
b KERNEL_S1_NEXT
KERNEL_S1_SCALE_GE_X:
fdiv s2, s4, SCALE
fmla SSQ, s2, v2.s[0]
fcvt d4, s4
#else
ldr d4, [X]
#endif
fcmp d4, REGZERO
beq KERNEL_S1_NEXT
fabs d4, d4
Expand All @@ -120,7 +92,6 @@ KERNEL_S1_SCALE_GE_X:
KERNEL_S1_SCALE_GE_X:
fdiv d2, d4, SCALE
fmla SSQ, d2, v2.d[0]
#endif
KERNEL_S1_NEXT:
add X, X, INC_X
.endm
Expand Down Expand Up @@ -218,7 +189,9 @@ KERNEL_S1_NEXT:
.Lnrm2_kernel_L999:
fsqrt SSQ, SSQ
fmul SSQ, SCALE, SSQ

#if !defined(DOUBLE)
fcvt SSQF, SSQ
#endif
ret

EPILOGUE
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