From cd02630da82b6b0a59583160b12c286a7aec7f8c Mon Sep 17 00:00:00 2001
From: Carter Sande <carter.sande@duodecima.technology>
Date: Mon, 24 Jun 2019 22:32:50 -0700
Subject: [PATCH 1/2] compiler-rt: Support thumb versions older than armv6

Add versions of __aeabi_memset and __aeabi_memclr which do not use mov
instructions between low registers, as this is unsupported on thumbv4t
and thumbv5.
---
 std/special/compiler_rt.zig | 43 +++++++++++++++++++++++++++++++++++--
 1 file changed, 41 insertions(+), 2 deletions(-)

diff --git a/std/special/compiler_rt.zig b/std/special/compiler_rt.zig
index 46607a3adf..95867d6952 100644
--- a/std/special/compiler_rt.zig
+++ b/std/special/compiler_rt.zig
@@ -471,6 +471,28 @@ test "usesThumb1" {
     //etc.
 }
 
+const use_thumb_1_pre_armv6 = usesThumb1PreArmv6(builtin.arch);
+
+fn usesThumb1PreArmv6(arch: builtin.Arch) bool {
+    return switch (arch) {
+        .thumb => switch (arch.thumb) {
+            .v5,
+            .v5te,
+            .v4t,
+            => true,
+            else => false,
+        },
+        .thumbeb => switch (arch.thumbeb) {
+            .v5,
+            .v5te,
+            .v4t,
+            => true,
+            else => false,
+        },
+        else => false,
+    };
+}
+
 nakedcc fn __aeabi_memcpy() noreturn {
     @setRuntimeSafety(false);
     if (use_thumb_1) {
@@ -505,7 +527,16 @@ nakedcc fn __aeabi_memmove() noreturn {
 
 nakedcc fn __aeabi_memset() noreturn {
     @setRuntimeSafety(false);
-    if (use_thumb_1) {
+    if (use_thumb_1_pre_armv6) {
+        asm volatile (
+            \\ eors    r1, r2
+            \\ eors    r2, r1
+            \\ eors    r1, r2
+            \\ push    {r7, lr}
+            \\ b       memset
+            \\ pop     {r7, pc}
+        );
+    } else if (use_thumb_1) {
         asm volatile (
             \\ mov     r3, r1
             \\ mov     r1, r2
@@ -527,7 +558,15 @@ nakedcc fn __aeabi_memset() noreturn {
 
 nakedcc fn __aeabi_memclr() noreturn {
     @setRuntimeSafety(false);
-    if (use_thumb_1) {
+    if (use_thumb_1_pre_armv6) {
+        asm volatile (
+            \\ adds    r2, r1, #0
+            \\ movs    r1, #0
+            \\ push    {r7, lr}
+            \\ bl      memset
+            \\ pop     {r7, pc}
+        );
+    } else if (use_thumb_1) {
         asm volatile (
             \\ mov     r2, r1
             \\ movs    r1, #0

From f9e26d98711ead110a4c2d2f3032978a5a8c2d9d Mon Sep 17 00:00:00 2001
From: Carter Sande <carter.sande@duodecima.technology>
Date: Tue, 25 Jun 2019 22:54:10 -0700
Subject: [PATCH 2/2] compiler-rt: use more idiomatic switch syntax

---
 std/special/compiler_rt.zig | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/std/special/compiler_rt.zig b/std/special/compiler_rt.zig
index 95867d6952..914f9dcb00 100644
--- a/std/special/compiler_rt.zig
+++ b/std/special/compiler_rt.zig
@@ -405,15 +405,15 @@ const use_thumb_1 = usesThumb1(builtin.arch);
 
 fn usesThumb1(arch: builtin.Arch) bool {
     return switch (arch) {
-        .arm => switch (arch.arm) {
+        .arm => |sub_arch| switch (sub_arch) {
             .v6m => true,
             else => false,
         },
-        .armeb => switch (arch.armeb) {
+        .armeb => |sub_arch| switch (sub_arch) {
             .v6m => true,
             else => false,
         },
-        .thumb => switch (arch.thumb) {
+        .thumb => |sub_arch| switch (sub_arch) {
             .v5,
             .v5te,
             .v4t,
@@ -423,7 +423,7 @@ fn usesThumb1(arch: builtin.Arch) bool {
             => true,
             else => false,
         },
-        .thumbeb => switch (arch.thumbeb) {
+        .thumbeb => |sub_arch| switch (sub_arch) {
             .v5,
             .v5te,
             .v4t,
@@ -475,18 +475,12 @@ const use_thumb_1_pre_armv6 = usesThumb1PreArmv6(builtin.arch);
 
 fn usesThumb1PreArmv6(arch: builtin.Arch) bool {
     return switch (arch) {
-        .thumb => switch (arch.thumb) {
-            .v5,
-            .v5te,
-            .v4t,
-            => true,
+        .thumb => |sub_arch| switch (sub_arch) {
+            .v5, .v5te, .v4t => true,
             else => false,
         },
-        .thumbeb => switch (arch.thumbeb) {
-            .v5,
-            .v5te,
-            .v4t,
-            => true,
+        .thumbeb => |sub_arch| switch (sub_arch) {
+            .v5, .v5te, .v4t => true,
             else => false,
         },
         else => false,