FS#11335 by me: make ARM assembly functions thumb-friendly

We can't pop into pc on ARMv4t when using thumb: the T bit won't be
modified if we are returning to a thumb function
Code running on ARMv4t should use the new ldrpc / ldmpc macros instead
of ldr pc, [sp], #4 and ldm(cond) sp!, {regs, pc}
No modification on pure ARM builds and ARMv5+

Note: USE_THUMB is currently never defined, no targets can currently be
built with -mthumb, see FS#6734

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@26756 a1c6a512-1295-4272-9138-f99709370657

1 files changed, 8 insertions, 3 deletions

diff --git a/firmware/target/arm/pcm-pp.c b/firmware/target/arm/pcm-pp.c
index 6289b4c730..bffc69f771 100644
--- a/firmware/target/arm/pcm-pp.c
+++ b/firmware/target/arm/pcm-pp.c
@@ -74,9 +74,14 @@ void fiq_handler(void) ICODE_ATTR __attribute__((naked));
 void fiq_handler(void)
 {
     asm volatile (
-        "ldr pc, [pc, #-4] \n"
-    "fiq_function:         \n"
-        ".word 0           \n"
+#if ARM_ARCH == 4 && defined(USE_THUMB)
+        "ldr r12, [pc, #-4] \n"
+        "bx  r12            \n"
+#else
+        "ldr pc, [pc, #-4]  \n"
+#endif
+    "fiq_function:          \n"
+        ".word 0            \n"
     );
 }