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authorWill Deacon <will.deacon@arm.com>2014-07-10 12:40:09 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2014-07-18 10:21:17 +0100
commit5959e25729a521097856d71528504deda1e11584 (patch)
treece4fc3bb9d6b573450ea8c947d94d49eaeb6dad3 /arch/arm64/include/asm/fpsimdmacros.h
parentad789ba5f7086138461420d2156478d33fb61077 (diff)
downloadlinux-5959e25729a521097856d71528504deda1e11584.tar.gz
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: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/include/asm/fpsimdmacros.h')
-rw-r--r--arch/arm64/include/asm/fpsimdmacros.h17
1 files changed, 15 insertions, 2 deletions
diff --git a/arch/arm64/include/asm/fpsimdmacros.h b/arch/arm64/include/asm/fpsimdmacros.h
index 768414d55e64..007618b8188c 100644
--- a/arch/arm64/include/asm/fpsimdmacros.h
+++ b/arch/arm64/include/asm/fpsimdmacros.h
@@ -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