https://bugs.gentoo.org/show_bug.cgi?id=896138
https://github.com/cisco/openh264/pull/3630

From f60e7d9bdc39e51b644db7624256116202cac992 Mon Sep 17 00:00:00 2001
From: matoro <matoro@users.noreply.github.com>
Date: Thu, 2 Mar 2023 17:39:45 -0500
Subject: [PATCH] Use environment for mips feature detection

The -march= option is perfectly happy to emit code to run on a processor
different than the one on which it is being compiled.  This results in
misdetection of mips features because the test compiles specify that a
given extension should be emitted, but this does not check whether or
not this corresponds to the subarchitecture targeted in CFLAGS by the
rest of the build.

$ echo "void main(void){ __asm__ volatile(\"punpcklhw \$f0, \$f0, \$f0\"); }" > test.c
$ CFLAGS="-march=loongson3a" make test
cc -march=loongson3a    test.c   -o test
$ ./test
Illegal instruction
$ CFLAGS="-march=native" make -B test
cc -march=native    test.c   -o test
/tmp/ccLbeyM1.s: Assembler messages:
/tmp/ccLbeyM1.s:25: Error: opcode not supported on this processor: octeon2 (mips64r2) `punpcklhw $f0,$f0,$f0'
make: *** [<builtin>: test] Error 1

This leads to -march=loongson3a getting appended to CFLAGS, which may
conflict with previously specified -march= levels for the build, or
other options.  Calling make in the test will use whatever CC/CFLAGS are
specified in the environment to determine whether the actual compile
command line to be used in the build supports these features.

Fixes: 8b942ee ("Adjust the mmi/msa detection mode for mips platform.")
---
 build/arch.mk                 |  8 ++++----
 build/loongarch-simd-check.sh | 17 +++++++----------
 build/mips-simd-check.sh      | 17 +++++++----------
 3 files changed, 18 insertions(+), 24 deletions(-)

diff --git a/build/arch.mk b/build/arch.mk
index 4e1538c45c..80983686f7 100644
--- a/build/arch.mk
+++ b/build/arch.mk
@@ -39,14 +39,14 @@ ASM_ARCH = mips
 ASMFLAGS += -I$(SRC_PATH)codec/common/mips/
 #mmi
 ifeq ($(ENABLE_MMI), Yes)
-ENABLE_MMI = $(shell $(SRC_PATH)build/mips-simd-check.sh $(CC) mmi)
+ENABLE_MMI = $(shell CC="$(CC)" CFLAGS="$(CFLAGS)" $(SRC_PATH)build/mips-simd-check.sh mmi)
 ifeq ($(ENABLE_MMI), Yes)
 CFLAGS += -DHAVE_MMI -march=loongson3a
 endif
 endif
 #msa
 ifeq ($(ENABLE_MSA), Yes)
-ENABLE_MSA = $(shell $(SRC_PATH)build/mips-simd-check.sh $(CC) msa)
+ENABLE_MSA = $(shell CC="$(CC)" CFLAGS="$(CFLAGS)" $(SRC_PATH)build/mips-simd-check.sh msa)
 ifeq ($(ENABLE_MSA), Yes)
 CFLAGS += -DHAVE_MSA -mmsa
 endif
@@ -63,14 +63,14 @@ ASM_ARCH = loongarch
 ASMFLAGS += -I$(SRC_PATH)codec/common/loongarch/
 #lsx
 ifeq ($(ENABLE_LSX), Yes)
-ENABLE_LSX = $(shell $(SRC_PATH)build/loongarch-simd-check.sh $(CC) lsx)
+ENABLE_LSX = $(shell CC="$(CC)" CFLAGS="$(CFLAGS)" $(SRC_PATH)build/loongarch-simd-check.sh lsx)
 ifeq ($(ENABLE_LSX), Yes)
 CFLAGS += -DHAVE_LSX -mlsx
 endif
 endif
 #lasx
 ifeq ($(ENABLE_LASX), Yes)
-ENABLE_LASX = $(shell $(SRC_PATH)build/loongarch-simd-check.sh $(CC) lasx)
+ENABLE_LASX = $(shell CC="$(CC)" CFLAGS="$(CFLAGS)" $(SRC_PATH)build/loongarch-simd-check.sh lasx)
 ifeq ($(ENABLE_LASX), Yes)
 CFLAGS += -DHAVE_LASX -mlasx
 endif
diff --git a/build/loongarch-simd-check.sh b/build/loongarch-simd-check.sh
index 597ddcdc22..2e609443b9 100755
--- a/build/loongarch-simd-check.sh
+++ b/build/loongarch-simd-check.sh
@@ -8,29 +8,26 @@
 #    lsx, lasx (maybe more in the future).
 #
 #   --usage:
-#             ./loongarch-simd-check.sh $(CC) lsx
-#         or  ./loongarch-simd-check.sh $(CC) lasx
+#             ./loongarch-simd-check.sh lsx
+#         or  ./loongarch-simd-check.sh lasx
 #
 # date:  11/23/2021 Created
 #***************************************************************************************
 
 TMPC=$(mktemp tmp.XXXXXX.c)
-TMPO=$(mktemp tmp.XXXXXX.o)
-if [ $2 == "lsx" ]
+if [ $1 == "lsx" ]
 then
    echo "void main(void){ __asm__ volatile(\"vadd.b \$vr0, \$vr1, \$vr1\"); }" > $TMPC
-   $1 -mlsx $TMPC -o $TMPO &> /dev/null
-   if test -s $TMPO
+   if make -f /dev/null "${TMPC/.c/.o}"
    then
       echo "Yes"
    fi
-elif [ $2 == "lasx" ]
+elif [ $1 == "lasx" ]
 then
    echo "void main(void){ __asm__ volatile(\"xvadd.b \$xr0, \$xr1, \$xr1\"); }" > $TMPC
-   $1 -mlasx $TMPC -o $TMPO &> /dev/null
-   if test -s $TMPO
+   if make -f /dev/null "${TMPC/.c/.o}"
    then
       echo "Yes"
    fi
 fi
-rm -f $TMPC $TMPO
+rm -f $TMPC
diff --git a/build/mips-simd-check.sh b/build/mips-simd-check.sh
index d0d72f9edd..5ff1eb432c 100755
--- a/build/mips-simd-check.sh
+++ b/build/mips-simd-check.sh
@@ -4,29 +4,26 @@
 #    mmi, msa (maybe more in the future).
 #
 #   --usage:
-#             ./mips-simd-check.sh $(CC) mmi
-#         or  ./mips-simd-check.sh $(CC) msa
+#             ./mips-simd-check.sh mmi
+#         or  ./mips-simd-check.sh msa
 #
 # date:  10/17/2019 Created
 #**********************************************************************************
 
 TMPC=$(mktemp tmp.XXXXXX.c)
-TMPO=$(mktemp tmp.XXXXXX.o)
-if [ $2 == "mmi" ]
+if [ $1 == "mmi" ]
 then
    echo "void main(void){ __asm__ volatile(\"punpcklhw \$f0, \$f0, \$f0\"); }" > $TMPC
-   $1 -march=loongson3a $TMPC -o $TMPO &> /dev/null
-   if test -s $TMPO
+   if make -f /dev/null "${TMPC/.c/.o}" &> /dev/null
    then
       echo "Yes"
    fi
-elif [ $2 == "msa" ]
+elif [ $1 == "msa" ]
 then
    echo "void main(void){ __asm__ volatile(\"addvi.b \$w0, \$w1, 1\"); }" > $TMPC
-   $1 -mmsa $TMPC -o $TMPO &> /dev/null
-   if test -s $TMPO
+   if make -f /dev/null "${TMPC/.c/.o}" &> /dev/null
    then
       echo "Yes"
    fi
 fi
-rm -f $TMPC $TMPO
+rm -f $TMPC