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From 233413841882608c6d5b98b6ce89fcb8a292db82 Mon Sep 17 00:00:00 2001
From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Date: Sat, 6 Aug 2016 10:22:34 +0200
Subject: [PATCH] configure.ac: fix architecture detection
The current architecture detection, based on the "host_cpu" part of the
tuple does not work properly for a number of reason:
- The code assumes that if host_cpu starts with "arm" then ARM
instructions are available, which is incorrect. Indeed, Cortex-M
platforms can run Linux, they are ARM platforms (so host_cpu = arm),
but they don't support ARM instructions: they support only the
Thumb-2 instruction set.
- The armv7 case is also not very useful, as it is not standard at all
to pass armv7 as host_cpu even if the host system is actually ARMv7
based.
- For the same reason, the armv8 case is not very useful: armv8 is
never used as the host_cpu part of a tuple.
So, this commit moves away from a host_cpu based logic, and instead
tests using AC_CHECK_DECLS() the built-in definitions of the compiler:
- If we have __ARM_ARCH_ISA_ARM defined, then it's an ARM processor
that supports the ARM instruction set (this allows to exclude Thumb-2
only processors).
- If we have __ARM_ARCH_7A__, then we have an ARMv7-A processor, and
we can enable the corresponding optimizations
- Same for __i386__ and __x86_64__.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
---
Submitted upstream, under a slightly different form so that it applies
on master:
https://lists.freedesktop.org/archives/pulseaudio-discuss/2016-August/026600.html
---
configure.ac | 27 +++++++++------------------
1 file changed, 9 insertions(+), 18 deletions(-)
diff --git a/configure.ac b/configure.ac
index 6f9553b..836c6ad 100644
--- a/configure.ac
+++ b/configure.ac
@@ -55,24 +55,15 @@ AS_CASE(["${host}"],
)
AC_SUBST(PLATFORM_CFLAGS)
-AS_CASE(["${host_cpu}"],
- [i?86|x86_64],
- [
- HAVE_X86=1
- ],
- [armv7*|armv8*],
- [
- HAVE_ARM=1
- HAVE_ARMV7=1
- ARCH_CFLAGS="-DWEBRTC_ARCH_ARM -DWEBRTC_ARCH_ARM_V7"
- ],
- [arm*],
- [
- HAVE_ARM=1
- ARCH_CFLAGS="-DWEBRTC_ARCH_ARM"
- ]
- # FIXME: Add MIPS support, see webrtc/BUILD.gn for defines
-)
+# Testing __ARM_ARCH_ISA_ARM since the code contains ARM instructions,
+# which don't work on Thumb-2 only platforms (ARMv7-M).
+AC_CHECK_DECLS([__ARM_ARCH_ISA_ARM],
+ [HAVE_ARM=1; ARCH_CFLAGS="${ARCH_CFLAGS} -DWEBRTC_ARCH_ARM"])
+AC_CHECK_DECLS([__ARM_ARCH_7A__],
+ [HAVE_ARMV7=1; ARCH_CFLAGS="${ARCH_CFLAGS} -DWEBRTC_ARCH_ARM_V7"])
+AC_CHECK_DECLS([__i386__], [HAVE_X86=1])
+AC_CHECK_DECLS([__x86_64__], [HAVE_X86=1])
+
AM_CONDITIONAL(HAVE_X86, [test "x${HAVE_X86}" = "x1"])
AM_CONDITIONAL(HAVE_ARM, [test "x${HAVE_ARM}" = "x1"])
AM_CONDITIONAL(HAVE_ARMV7, [test "x${HAVE_ARMV7}" = "x1"])
--
2.7.4
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