[PATCH v2] libc: arm: Implement setjmp GCC backwards compatibility.
Victor L. Do Nascimento
victor.donascimento@arm.com
Fri Feb 3 11:15:26 GMT 2023
When compiling Newlib for arm targets with GCC 12.1 onward, the
passing of architecture extension information to the assembler is
automatic, making the use of .fpu and .arch_extension directives
in assembly files redundant.
With older versions of GCC, however, these directives must be
hard-coded into the `arm/setjmp.S' file to allow the assembly of
instructions concerning the storage and subsequent reloading of the
floating point registers to/from the jump buffer, respectively.
This patch conditionally adds the `.fpu vfpxd' and `.arch_extension
mve' directives based on compile-time preprocessor macros concerning
GCC version and target architectural features, such that both the
assembly and linking of setjmp.S succeeds for older versions of
Newlib.
---
newlib/libc/machine/arm/setjmp.S | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/newlib/libc/machine/arm/setjmp.S b/newlib/libc/machine/arm/setjmp.S
index c615f2428..5401534cd 100644
--- a/newlib/libc/machine/arm/setjmp.S
+++ b/newlib/libc/machine/arm/setjmp.S
@@ -64,6 +64,28 @@
.syntax unified
+/* GCC 12.1 and later will tell the assembler exactly which floating
+ point (or MVE) unit is required and we don't want to override
+ that. Conversely, older versions of the compiler don't pass this
+ information so we need to enable the VFP version that is most
+ appropriate. The choice here should support all suitable VFP
+ versions that the older toolchains can handle. */
+#if __GNUC__ && __GNUC__ < 12
+/* Ensure that FPU instructions are correctly compiled and, likewise,
+ the appropriate build attributes are added to the resulting object
+ file. Check whether the MVE extension is present and whether
+ we have support for hardware floating point-operations. VFPxd
+ covers all the cases we need in this file for hardware
+ floating-point and should be compatible with all required FPUs
+ that we need to support. */
+# if __ARM_FP
+ .fpu vfpxd
+# endif
+# if __ARM_FEATURE_MVE
+ .arch_extension mve
+# endif
+#endif
+
#if __ARM_ARCH_ISA_THUMB == 1 && !__ARM_ARCH_ISA_ARM
/* ARMv6-M-like has to be implemented in Thumb mode. */
--
2.36.1
More information about the Newlib
mailing list