From a5c869c1f64deaf945dcccd50b4043f3f0d71f03 Mon Sep 17 00:00:00 2001
From: Brandon Bergren <bdragon@FreeBSD.org>
Date: Tue, 8 Sep 2020 01:27:03 +0000
Subject: [PATCH] [PowerPC] Work around -O miscompile on powerpc 32 bit.

Work around llvm 11 miscompile in 32 bit powerpc that appears to cause ifuncs
to branch to the wrong address by forcing -O2. This worked in previous
versions because -O was mapped to -O2 previously (but is now -O1.)

While here, remove the old temporary workaround from r224882 that does the
opposite thing for powerpc non-DEBUG kernels, bringing it in line with other
platforms that compile at -O2.

This fixes kernel boot on powerpc and powerpcspe after the llvm11 transition.

Sponsored by:	Tag1 Consulting, Inc.
---
 sys/conf/kern.pre.mk | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/sys/conf/kern.pre.mk b/sys/conf/kern.pre.mk
index 58b1d021087..dea42571e9c 100644
--- a/sys/conf/kern.pre.mk
+++ b/sys/conf/kern.pre.mk
@@ -51,15 +51,16 @@ OBJCOPY?=	objcopy
 SIZE?=		size
 
 .if defined(DEBUG)
+.if ${MACHINE_ARCH} == "powerpc" || ${MACHINE_ARCH} == "powerpcspe"
+# Work around clang 11 miscompile on 32 bit powerpc.
+_MINUS_O=	-O2
+.else
 _MINUS_O=	-O
+.endif
 CTFFLAGS+=	-g
 .else
-.if ${MACHINE_CPUARCH} == "powerpc"
-_MINUS_O=	-O	# gcc miscompiles some code at -O2
-.else
 _MINUS_O=	-O2
 .endif
-.endif
 .if ${MACHINE_CPUARCH} == "amd64"
 .if ${COMPILER_TYPE} == "clang"
 COPTFLAGS?=-O2 -pipe
-- 
2.45.0