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aarch64: Remove useless _curr_cpu struct #33181

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Merged
merged 1 commit into from
Apr 9, 2021
Merged

aarch64: Remove useless _curr_cpu struct #33181

merged 1 commit into from
Apr 9, 2021

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@carlocaione
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@carlocaione carlocaione commented Mar 9, 2021 •
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small fix suggested by @jharris-intel.

Please note that if this is merged before #32854 we will have to fix the userspace PR because get_cpu now needs 3 registers to be clobbered.

@github-actions github-actions bot added area: ARM ARM (32-bit) Architecture area: ARM_64 area: Kernel labels Mar 9, 2021
@npitre
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npitre commented Mar 9, 2021

You could save one insn by combining the symbol with an offset:

diff --git a/arch/arm/core/aarch64/macro_priv.inc b/arch/arm/core/aarch64/macro_priv.inc
index 298fc18216..a85ff2ef1e 100644
--- a/arch/arm/core/aarch64/macro_priv.inc
+++ b/arch/arm/core/aarch64/macro_priv.inc
@@ -27,8 +27,7 @@ GDATA(_kernel)
 
 .macro get_cpu xreg0, xreg1, xreg2
 	get_cpu_id \xreg1
-	ldr	\xreg0, =_kernel
-	add	\xreg0, \xreg0, #___kernel_t_cpus_OFFSET
+	ldr	\xreg0, =(_kernel + ___kernel_t_cpus_OFFSET)
 	mov	\xreg2, #___cpu_t_SIZEOF
 	madd	\xreg0, \xreg1, \xreg2, \xreg0
 .endm

@carlocaione
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carlocaione commented Mar 9, 2021 •
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You could save one insn by combining the symbol with an offset:

ah! indeed. And it's even nicer. Fixing it.

jharris-intel
jharris-intel approved these changes Mar 9, 2021
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@zephyrbot zephyrbot added the area: ARM64 ARM (64-bit) Architecture label Mar 10, 2021
@zephyrbot zephyrbot requested review from ceolin and pabigot March 10, 2021 11:13
@carlocaione
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carlocaione commented Mar 18, 2021

@nashif can you merge this?

@carlocaione
aarch64: Remove useless _curr_cpu struct
99ae81e 
Currently _curr_cpu is only used by the get_cpu macro to quickly access
the cpu struct. This is not really necessary because we can access to
the struct by directly referencing &(_kernel.cpus[cpu_num]) in assembly

Signed-off-by: Carlo Caione <ccaione@baylibre.com>
@carlocaione carlocaione mentioned this pull request Apr 9, 2021
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@nashif nashif merged commit 64dfa69 into zephyrproject-rtos:master Apr 9, 2021
@carlocaione carlocaione deleted the remove_curr_cpu branch April 9, 2021 12:29
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@nashif nashif nashif approved these changes

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