55 lines
2.2 KiB
Diff
55 lines
2.2 KiB
Diff
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From 3e40f9669279f005f7154892539166f5081fbcb2 Mon Sep 17 00:00:00 2001
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From: Vineet Gupta <Vineet.Gupta1@synopsys.com>
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Date: Tue, 16 Aug 2016 15:04:27 -0700
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Subject: [PATCH] ARC: Support syscall ABI v4
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The syscall ABI includes the gcc functional calling ABI since a syscall
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implies userland caller and kernel callee.
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The current gcc ABI (v3) for ARCv2 ISA required 64-bit data be passed in
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even-odd register pairs, (potentially punching reg holes when passing such
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values as args). This was partly driven by the fact that the double-word
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LDD/STD instructions in ARCv2 expect the register alignment and thus gcc
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forcing this avoids extra MOV at the cost of a few unused register (which we
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have plenty anyways).
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This however was rejected as part of upstreaming gcc port to HS. So the new
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ABI v4 doesn't enforce the even-odd reg restriction.
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Do note that for ARCompact ISA builds v3 and v4 are practically the same in
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terms of gcc code generation.
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This change is dormant for now (gcc 4.8.x based tools) and will only kick
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in with switch to gcc 6.x based tools.
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Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
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Signed-off-by: Vlad Zakharov <vzakhar@synopsys.com>
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---
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libc/sysdeps/linux/arc/bits/uClibc_arch_features.h | 10 ++++++++--
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1 file changed, 8 insertions(+), 2 deletions(-)
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diff --git a/libc/sysdeps/linux/arc/bits/uClibc_arch_features.h b/libc/sysdeps/linux/arc/bits/uClibc_arch_features.h
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index 5160724..94e089d 100755
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--- a/libc/sysdeps/linux/arc/bits/uClibc_arch_features.h
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+++ b/libc/sysdeps/linux/arc/bits/uClibc_arch_features.h
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@@ -41,8 +41,14 @@
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/* The default ';' is a comment on ARC. */
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#define __UCLIBC_ASM_LINE_SEP__ `
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-/* does your target align 64bit values in register pairs ? (32bit arches only) */
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-#if defined(__A7__)
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+/* does your target align 64bit values in register pairs ? (32bit arches only)
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+ * - ARC700 never had any constraint on reg pairs (even if ABI v3)
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+ * - Inital HS ABI (v3: non upstream gcc) had 64-bit data aligned in even-odd
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+ * reg pairs (thus allowed reg holes when passing such args to calls)
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+ * - Upstream gcc (6.x) HS ABI doesn't have that restriction
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+ */
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+
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+#if defined(__A7__) || (__GNUC__ > 4)
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#undef __UCLIBC_SYSCALL_ALIGN_64BIT__
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#else
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#define __UCLIBC_SYSCALL_ALIGN_64BIT__
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--
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2.7.4
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