From: "Victor L. Do Nascimento" <victor.donascimento@arm.com>
To: <newlib@sourceware.org>
Cc: <richard.earnshaw@arm.com>
Subject: [PATCH] libc: arm: Implement setjmp GCC backwards compatibility.
Date: Wed, 1 Feb 2023 15:10:18 +0000 [thread overview]
Message-ID: <yw8ja61xxvz9.fsf@arm.com> (raw)
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' directives instructions in assembly files
redundant.
With older versions of GCC, however, the .fpu directive 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' directive 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 | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/newlib/libc/machine/arm/setjmp.S b/newlib/libc/machine/arm/setjmp.S
index c615f2428..3a9aa840d 100644
--- a/newlib/libc/machine/arm/setjmp.S
+++ b/newlib/libc/machine/arm/setjmp.S
@@ -64,6 +64,22 @@
.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
+/* While GCC > 10.1 supports MVE, the MVE instructions do not need an
+ .fpu directive, so we don't need to handle that case. VFPxd thus
+ covers all the cases we need in this file and should be compatible
+ with all required FPUs that we need to support. */
+# if __ARM_FP
+ .fpu vfpxd
+# 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
next reply other threads:[~2023-02-01 15:10 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-01 15:10 Victor L. Do Nascimento [this message]
2023-02-02 11:41 ` Richard Earnshaw
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