Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 5959e257 authored by Will Deacon's avatar Will Deacon Committed by Catalin Marinas
Browse files

arm64: fpsimd: avoid restoring fpcr if the contents haven't changed 



Writing to the FPCR is commonly implemented as a self-synchronising
operation in the CPU, so avoid writing to the register when the saved
value matches that in the hardware already.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: default avatarLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent ad789ba5

arch/arm64/include/asm/fpsimdmacros.h

+15 −2
Original line number Diff line number Diff line
@@ -40,6 +40,19 @@ 
	str	w\tmpnr, [\state, #16 * 2 + 4]

.endm



.macro fpsimd_restore_fpcr state, tmp

	/*

	 * Writes to fpcr may be self-synchronising, so avoid restoring

	 * the register if it hasn't changed.

	 */

	mrs	\tmp, fpcr

	cmp	\tmp, \state

	b.eq	9999f

	msr	fpcr, \state

9999:

.endm



/* Clobbers \state */

.macro fpsimd_restore state, tmpnr

	ldp	q0, q1, [\state, #16 * 0]

	ldp	q2, q3, [\state, #16 * 2]
@@ -60,7 +73,7 @@ 
	ldr	w\tmpnr, [\state, #16 * 2]

	msr	fpsr, x\tmpnr

	ldr	w\tmpnr, [\state, #16 * 2 + 4]

	msr	fpcr, x\tmpnr

	fpsimd_restore_fpcr x\tmpnr, \state

.endm



.altmacro
@@ -84,7 +97,7 @@ 
.macro fpsimd_restore_partial state, tmpnr1, tmpnr2

	ldp	w\tmpnr1, w\tmpnr2, [\state]

	msr	fpsr, x\tmpnr1

	msr	fpcr, x\tmpnr2

	fpsimd_restore_fpcr x\tmpnr2, x\tmpnr1

	adr	x\tmpnr1, 0f

	ldr	w\tmpnr2, [\state, #8]

	add	\state, \state, x\tmpnr2, lsl #4