nixpkgs/pkgs/development/compilers/llvm/common/compiler-rt/armv6-no-ldrexd-strexd.patch
Ben Wolsieffer 98ebcd28e1 compiler-rt: fix build on ARMv6
compiler-rt has accumulated several regressions that prevent it from building
on ARMv6. It is important to note that there are two major versions of ARMv6:
base ARMv6 and ARMv6K. ARMv6K includes several important new instructions,
such as non-word size atomic operations (ldrexd, strexd, etc.) and the yield
instruction. Most ARMv6 CPUs actually implement ARMv6K, including all those used
in Raspberry Pis, but nixpkgs' "raspberryPi" platform targets base ARMv6.

compiler-rt versions 8-14 fail to build on ARMv6 and ARMv6K. compiler-rt 15 (not
yet in nixpkgs) builds on ARMv6K but not ARMv6. This patch fixes versions 9-14
on both ARMv6 variants. The patches don't apply cleanly to version 8, and I
figured it wasn't worth carrying another version of the patches for such an old
version.

A total of five patches are required to get compiler-rt building on ARMv6:
* armv6-mcr-dmb.patch: use `mcr` to provide the equivalent of `dmb` on ARMv6.
  Included in LLVM 15.
* armv6-sync-ops-no-thumb.patch: prevent certain atomic operation functions
  from using Thumb mode. Included in LLVM 15.
* armv6-no-ldrexd-strexd.patch: don't use ldrexd or strexd, which are not
  available in base ARMv6. Submitted upstream by me.
* armv6-scudo-no-yield.patch: use nop instead of yield on ARMv6 in standalone
  scudo. Required by versions >=13, since they enable standalone scudo.
  Submitted upstream by me.
* armv6-scudo-libatomic.patch: link standlone scudo to libatomic on ARMv6 (and
  any other platforms that need it). Not yet submitted because the backport is
  a bit different from the upstream version and I need to test it.
2023-03-08 14:27:35 -05:00

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Diff

From 4fe3f21bf8b20c766877d2251d61118d0ff36688 Mon Sep 17 00:00:00 2001
From: Ben Wolsieffer <benwolsieffer@gmail.com>
Date: Wed, 7 Dec 2022 14:56:51 -0500
Subject: [PATCH] [compiler-rt][builtins] Do not use ldrexd or strexd on ARMv6
The ldrexd and strexd instructions are not available on base ARMv6, and were
only added in ARMv6K (see [1]). This patch solves this problem once and for all
using the __ARM_FEATURE_LDREX macro (see [2]) defined in the ARM C Language
Extensions (ACLE). Although this macro is technically deprecated in the ACLE,
it allows compiler-rt to reliably detect whether ldrexd and strexd are supported
without complicated conditionals to detect different ARM architecture variants.
[1] https://developer.arm.com/documentation/dht0008/a/ch01s02s01
[2] https://arm-software.github.io/acle/main/acle.html#ldrexstrex
Differential Revision: https://reviews.llvm.org/D139585
---
compiler-rt/lib/builtins/arm/sync_fetch_and_add_8.S | 2 +-
compiler-rt/lib/builtins/arm/sync_fetch_and_and_8.S | 2 +-
compiler-rt/lib/builtins/arm/sync_fetch_and_max_8.S | 2 +-
compiler-rt/lib/builtins/arm/sync_fetch_and_min_8.S | 2 +-
compiler-rt/lib/builtins/arm/sync_fetch_and_nand_8.S | 2 +-
compiler-rt/lib/builtins/arm/sync_fetch_and_or_8.S | 2 +-
compiler-rt/lib/builtins/arm/sync_fetch_and_sub_8.S | 2 +-
compiler-rt/lib/builtins/arm/sync_fetch_and_umax_8.S | 2 +-
compiler-rt/lib/builtins/arm/sync_fetch_and_umin_8.S | 2 +-
compiler-rt/lib/builtins/arm/sync_fetch_and_xor_8.S | 2 +-
10 files changed, 10 insertions(+), 10 deletions(-)
diff --git a/lib/builtins/arm/sync_fetch_and_add_8.S b/lib/builtins/arm/sync_fetch_and_add_8.S
index 18bdd875b8b7..bee6f7ba0f34 100644
--- a/lib/builtins/arm/sync_fetch_and_add_8.S
+++ b/lib/builtins/arm/sync_fetch_and_add_8.S
@@ -13,7 +13,7 @@
#include "sync-ops.h"
-#if __ARM_ARCH_PROFILE != 'M'
+#if __ARM_FEATURE_LDREX & 8
#define add_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
adds rD_LO, rN_LO, rM_LO ; \
adc rD_HI, rN_HI, rM_HI
diff --git a/lib/builtins/arm/sync_fetch_and_and_8.S b/lib/builtins/arm/sync_fetch_and_and_8.S
index 3716eff809d5..b4e77a54edf6 100644
--- a/lib/builtins/arm/sync_fetch_and_and_8.S
+++ b/lib/builtins/arm/sync_fetch_and_and_8.S
@@ -13,7 +13,7 @@
#include "sync-ops.h"
-#if __ARM_ARCH_PROFILE != 'M'
+#if __ARM_FEATURE_LDREX & 8
#define and_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
and rD_LO, rN_LO, rM_LO ; \
and rD_HI, rN_HI, rM_HI
diff --git a/lib/builtins/arm/sync_fetch_and_max_8.S b/lib/builtins/arm/sync_fetch_and_max_8.S
index 06115ab55246..1813274cc649 100644
--- a/lib/builtins/arm/sync_fetch_and_max_8.S
+++ b/lib/builtins/arm/sync_fetch_and_max_8.S
@@ -13,7 +13,7 @@
#include "sync-ops.h"
-#if __ARM_ARCH_PROFILE != 'M'
+#if __ARM_FEATURE_LDREX & 8
#define max_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) MINMAX_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI, gt)
SYNC_OP_8(max_8)
diff --git a/lib/builtins/arm/sync_fetch_and_min_8.S b/lib/builtins/arm/sync_fetch_and_min_8.S
index 4f3e299d95cc..fa8f3477757b 100644
--- a/lib/builtins/arm/sync_fetch_and_min_8.S
+++ b/lib/builtins/arm/sync_fetch_and_min_8.S
@@ -13,7 +13,7 @@
#include "sync-ops.h"
-#if __ARM_ARCH_PROFILE != 'M'
+#if __ARM_FEATURE_LDREX & 8
#define min_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) MINMAX_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI, lt)
SYNC_OP_8(min_8)
diff --git a/lib/builtins/arm/sync_fetch_and_nand_8.S b/lib/builtins/arm/sync_fetch_and_nand_8.S
index 425c94474af7..fb27219ee200 100644
--- a/lib/builtins/arm/sync_fetch_and_nand_8.S
+++ b/lib/builtins/arm/sync_fetch_and_nand_8.S
@@ -13,7 +13,7 @@
#include "sync-ops.h"
-#if __ARM_ARCH_PROFILE != 'M'
+#if __ARM_FEATURE_LDREX & 8
#define nand_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
bic rD_LO, rN_LO, rM_LO ; \
bic rD_HI, rN_HI, rM_HI
diff --git a/lib/builtins/arm/sync_fetch_and_or_8.S b/lib/builtins/arm/sync_fetch_and_or_8.S
index 4f18dcf84df9..3b077c8737b1 100644
--- a/lib/builtins/arm/sync_fetch_and_or_8.S
+++ b/lib/builtins/arm/sync_fetch_and_or_8.S
@@ -13,7 +13,7 @@
#include "sync-ops.h"
-#if __ARM_ARCH_PROFILE != 'M'
+#if __ARM_FEATURE_LDREX & 8
#define or_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
orr rD_LO, rN_LO, rM_LO ; \
orr rD_HI, rN_HI, rM_HI
diff --git a/lib/builtins/arm/sync_fetch_and_sub_8.S b/lib/builtins/arm/sync_fetch_and_sub_8.S
index 25a4a1076555..c171607eabd8 100644
--- a/lib/builtins/arm/sync_fetch_and_sub_8.S
+++ b/lib/builtins/arm/sync_fetch_and_sub_8.S
@@ -13,7 +13,7 @@
#include "sync-ops.h"
-#if __ARM_ARCH_PROFILE != 'M'
+#if __ARM_FEATURE_LDREX & 8
#define sub_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
subs rD_LO, rN_LO, rM_LO ; \
sbc rD_HI, rN_HI, rM_HI
diff --git a/lib/builtins/arm/sync_fetch_and_umax_8.S b/lib/builtins/arm/sync_fetch_and_umax_8.S
index aa5213ff1def..d1224f758049 100644
--- a/lib/builtins/arm/sync_fetch_and_umax_8.S
+++ b/lib/builtins/arm/sync_fetch_and_umax_8.S
@@ -13,7 +13,7 @@
#include "sync-ops.h"
-#if __ARM_ARCH_PROFILE != 'M'
+#if __ARM_FEATURE_LDREX & 8
#define umax_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) MINMAX_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI, hi)
SYNC_OP_8(umax_8)
diff --git a/lib/builtins/arm/sync_fetch_and_umin_8.S b/lib/builtins/arm/sync_fetch_and_umin_8.S
index 8b40541ab47d..595444e6d053 100644
--- a/lib/builtins/arm/sync_fetch_and_umin_8.S
+++ b/lib/builtins/arm/sync_fetch_and_umin_8.S
@@ -13,7 +13,7 @@
#include "sync-ops.h"
-#if __ARM_ARCH_PROFILE != 'M'
+#if __ARM_FEATURE_LDREX & 8
#define umin_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) MINMAX_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI, lo)
SYNC_OP_8(umin_8)
diff --git a/lib/builtins/arm/sync_fetch_and_xor_8.S b/lib/builtins/arm/sync_fetch_and_xor_8.S
index 7436eb1d4cae..9fc3d85cef75 100644
--- a/lib/builtins/arm/sync_fetch_and_xor_8.S
+++ b/lib/builtins/arm/sync_fetch_and_xor_8.S
@@ -13,7 +13,7 @@
#include "sync-ops.h"
-#if __ARM_ARCH_PROFILE != 'M'
+#if __ARM_FEATURE_LDREX & 8
#define xor_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
eor rD_LO, rN_LO, rM_LO ; \
eor rD_HI, rN_HI, rM_HI
--
2.38.1