[RFC PATCH v2 3/8] arm64/fpsimdmacros: Allow the macro "for" to be used in more cases

From: Julien Grall <julien.grall@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: Anton.Kirilov@arm.com, catalin.marinas@arm.com,
	will.deacon@arm.com, oleg@redhat.com, zhang.lei@jp.fujitsu.com,
	Julien Grall <julien.grall@arm.com>,
	alex.bennee@linaro.org, Dave Martin <dave.martin@arm.com>,
	Daniel.Kiss@arm.com
Subject: [RFC PATCH v2 3/8] arm64/fpsimdmacros: Allow the macro "for" to be used in more cases
Date: Thu, 13 Jun 2019 17:16:51 +0100	[thread overview]
Message-ID: <20190613161656.20765-4-julien.grall@arm.com> (raw)
In-Reply-To: <20190613161656.20765-1-julien.grall@arm.com>

The current version of the macro "for" is only able to work when the
counter is used to generate registers using mnemonics. This is because
gas is not able to evaluate the expression generated if used in
registers name (i.e x\n).

Gas offers a way to evaluate macro arguments by using % in front of
them under the alternate macro mode [1].

The implementation of "for" is updated to use the alternate macro mode
and %, so we can use the macro in more cases. As the alternate macro mode
may have side-effect, this is disabled when generating the body.

While it is enough to prefix the argument of the macro "__for_body" with
%, the arguments of "__for" are also prefixed to get a more bearable
value in case of compilation error.

[1] https://sourceware.org/binutils/docs/as/Altmacro.html

Suggested-by: Dave Martin <dave.martin@arm.com>
Signed-off-by: Julien Grall <julien.grall@arm.com>

---
    Changes in v2:
        - Fix typo in the commit message
---
 arch/arm64/include/asm/fpsimdmacros.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/fpsimdmacros.h b/arch/arm64/include/asm/fpsimdmacros.h
index 46843515d77b..e2ab77dd9b4f 100644
--- a/arch/arm64/include/asm/fpsimdmacros.h
+++ b/arch/arm64/include/asm/fpsimdmacros.h
@@ -177,19 +177,23 @@
 
 .macro __for from:req, to:req
 	.if (\from) == (\to)
-		_for__body \from
+		_for__body %\from
 	.else
-		__for \from, (\from) + ((\to) - (\from)) / 2
-		__for (\from) + ((\to) - (\from)) / 2 + 1, \to
+		__for %\from, %((\from) + ((\to) - (\from)) / 2)
+		__for %((\from) + ((\to) - (\from)) / 2 + 1), %\to
 	.endif
 .endm
 
 .macro _for var:req, from:req, to:req, insn:vararg
 	.macro _for__body \var:req
+		.noaltmacro
 		\insn
+		.altmacro
 	.endm
 
+	.altmacro
 	__for \from, \to
+	.noaltmacro
 
 	.purgem _for__body
 .endm
-- 
2.11.0


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