toolchain: Fix toolchain to create proper builds for MIPS XBurst targets

This patch is need for example for ci20, -mfused-madd is deprecated, we need to use -ffp-contract instead.

This is basically a resubmission of
https://patchwork.ozlabs.org/patch/800406/

Please consider accepting the original patch, otherwise buildroot is basically broken for ci20 and similar platforms.

---
 toolchain/toolchain-wrapper.c  | 4 ++--
 toolchain/toolchain-wrapper.mk | 3 ++-
 2 files changed, 4 insertions(+), 3 deletions(-)

index 2928ea4..822bcdc 100644
@@ -79,8 +79,8 @@ static char *predef_args[] = {
 #ifdef BR_OMIT_LOCK_PREFIX
 	"-Wa,-momit-lock-prefix=yes",
 #endif
-#ifdef BR_NO_FUSED_MADD
-	"-mno-fused-madd",
+#ifdef BR_FP_CONTRACT_OFF
+   "-ffp-contract=off",
 #endif
 #ifdef BR_BINFMT_FLAT
 	"-Wl,-elf2flt",

index 7f72a0c..ecf67a4 100644
@@ -27,8 +27,9 @@ TOOLCHAIN_WRAPPER_ARGS += -DBR_OMIT_LOCK_PREFIX
 endif
 
 # Avoid FPU bug on XBurst CPUs
+# -mfused-madd is deprecated, use -ffp-contract instead
 ifeq ($(BR2_mips_xburst),y)
-TOOLCHAIN_WRAPPER_ARGS += -DBR_NO_FUSED_MADD
+TOOLCHAIN_WRAPPER_ARGS += -DBR_FP_CONTRACT_OFF
 endif
 
 ifeq ($(BR2_CCACHE_USE_BASEDIR),y)

2.7.4

Hello,

This is PATCH 2/2, we haven't received PATCH 1/2 in the mailing list. Where is it?

Is your patch a resubmission, or an additional patch ? You say it's a resubmission, and then the next paragraph you say we should also apply the original patch.

Also, the commit log should explain since which gcc version is -mfused-madd deprecated, and since which gcc version is -ffp-contract available.

Thanks!

Thomas

Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Am 05.01.2018 21:27 schrieb "Thomas Petazzoni" <
[email protected]>:

Hello,

This is PATCH 2/2, we haven't received PATCH 1/2 in the mailing list. Where is it?

Is your patch a resubmission, or an additional patch ? You say it's a resubmission, and then the next paragraph you say we should also apply the original patch.

It was not my own patch but I want to help bringing it up again because the original author complained that so far it hasn't been accepted. He recommended me to try it and see if it helps and it did help.

Also, the commit log should explain since which gcc version is -mfused-madd deprecated, and since which gcc version is -ffp-contract available.

I don't know this, my knowledge is incomplete in this area. I just manually applied the original patch. What can we do together to get this patch to an acceptable state?
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Hello Johannes,

Could you please send a complete patch that includes both Waldemar changes and yours ? Also, please read the comments in
https://patchwork.ozlabs.org/patch/800406/, they pointed out the fact that -ffp-contract only exists since gcc 4.6, so its use should be made conditional. Read the comments from Arnout, who suggests how to address that.

Thanks a lot!

Thomas

Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com