[PATCH, gcc/MIPS] Add options to disable/enable madd.fmt/msub.fmt instructions

[Yunqiang Su <Yunqiang dot Su at imgtec dot com>]

[PATCH] Add options to disable/enable madd.fmt/msub.fmt instructions

The build-time options are:
  --with-unfused-madd4=yes/no
  --without-unfused-madd4

The runtime options are:
  -munfused-madd4
  -mno-unfused-madd4

These options are needed due to madd.fmt/msub.fmt on some
platform is broken, which may generate wrong calculator result.
diff --git a/gcc/config.gcc b/gcc/config.gcc
index 7afbc54bc78..a3fdb0273c0 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -3940,7 +3940,7 @@ case "${target}" in
 		;;
 
 	mips*-*-*)
-		supported_defaults="abi arch arch_32 arch_64 float fpu nan fp_32 odd_spreg_32 tune tune_32 tune_64 divide llsc mips-plt synci"
+		supported_defaults="abi arch arch_32 arch_64 float fpu nan fp_32 odd_spreg_32 unfused_madd4 tune tune_32 tune_64 divide llsc mips-plt synci"
 
 		case ${with_float} in
 		"" | soft | hard)
@@ -3997,6 +3997,19 @@ case "${target}" in
 			exit 1
 			;;
 		esac
+		
+		case ${with_unfused_madd4} in
+		"" | yes)
+			with_unfused_madd4="unfused-madd4"
+			;;
+		no)
+			with_unfused_madd4="no-unfused-madd4"
+			;;
+		*)
+			echo "Unknown unfused_madd4 type used in --with-unfused-madd4=$with_unfused_madd4" 1>&2
+			exit 1
+			;;
+		esac
 
 		case ${with_abi} in
 		"" | 32 | o64 | n32 | 64 | eabi)
@@ -4496,7 +4509,7 @@ case ${target} in
 esac
 
 t=
-all_defaults="abi cpu cpu_32 cpu_64 arch arch_32 arch_64 tune tune_32 tune_64 schedule float mode fpu nan fp_32 odd_spreg_32 divide llsc mips-plt synci tls"
+all_defaults="abi cpu cpu_32 cpu_64 arch arch_32 arch_64 tune tune_32 tune_64 schedule float mode fpu nan fp_32 odd_spreg_32 unfused_madd4 divide llsc mips-plt synci tls"
 for option in $all_defaults
 do
 	eval "val=\$with_"`echo $option | sed s/-/_/g`
diff --git a/gcc/config/mips/mips.c b/gcc/config/mips/mips.c
index c7eb2a8e7bd..c2c231a483c 100644
--- a/gcc/config/mips/mips.c
+++ b/gcc/config/mips/mips.c
@@ -19829,6 +19829,16 @@ mips_option_override (void)
          will be produced.  */
       target_flags |= MASK_ODD_SPREG;
     }
+  
+  /* If neither -munfused-madd nor -mno-unfused-madd was given on the command
+     line, set MASK_UNFSUED_MADD based on the ISA.  */
+  if ((target_flags_explicit & MASK_UNFUSED_MADD4) == 0)
+    {
+      if (!ISA_HAS_UNFUSED_MADD4)
+	target_flags &= ~MASK_UNFUSED_MADD4;
+      else
+	target_flags |= MASK_UNFUSED_MADD4;
+    }
 
   if (!ISA_HAS_COMPACT_BRANCHES && mips_cb == MIPS_CB_ALWAYS)
     {
diff --git a/gcc/config/mips/mips.h b/gcc/config/mips/mips.h
index bb66c428dd1..6cf571906a6 100644
--- a/gcc/config/mips/mips.h
+++ b/gcc/config/mips/mips.h
@@ -863,6 +863,7 @@ struct mips_cpu_info {
 	    ":%{!msoft-float:%{!msingle-float:%{!mfp*:%{!mmsa:-mfp%(VALUE)}}}}}" }, \
   {"odd_spreg_32", "%{" OPT_ARCH32 ":%{!msoft-float:%{!msingle-float:" \
 		   "%{!modd-spreg:%{!mno-odd-spreg:-m%(VALUE)}}}}}" }, \
+  {"unfused_madd4", "%{!munfused-madd4:%{!mno-unfused-madd4:-m%(VALUE)}}" }, \
   {"divide", "%{!mdivide-traps:%{!mdivide-breaks:-mdivide-%(VALUE)}}" }, \
   {"llsc", "%{!mllsc:%{!mno-llsc:-m%(VALUE)}}" }, \
   {"mips-plt", "%{!mplt:%{!mno-plt:-m%(VALUE)}}" }, \
@@ -1060,7 +1061,7 @@ struct mips_cpu_info {
 
 /* ISA has 4 operand unfused madd instructions of the form
    'd = [+-] (a * b [+-] c)'.  */
-#define ISA_HAS_UNFUSED_MADD4	(ISA_HAS_FP4 && !TARGET_MIPS8000)
+#define ISA_HAS_UNFUSED_MADD4	(ISA_HAS_FP4 && !TARGET_MIPS8000 && TARGET_UNFUSED_MADD4)
 
 /* ISA has 3 operand r6 fused madd instructions of the form
    'c = c [+-] (a * b)'.  */
diff --git a/gcc/config/mips/mips.opt b/gcc/config/mips/mips.opt
index 08dd83e14ce..b154752a0df 100644
--- a/gcc/config/mips/mips.opt
+++ b/gcc/config/mips/mips.opt
@@ -416,6 +416,10 @@ modd-spreg
 Target Report Mask(ODD_SPREG)
 Enable use of odd-numbered single-precision registers.
 
+munfused-madd4
+Target Report Mask(UNFUSED_MADD4)
+Enable unfused multiply-add/multiply-sub instruction, aka madd.fmt/msub.fmt.
+
 mframe-header-opt
 Target Report Var(flag_frame_header_optimization) Optimization
 Optimize frame header.
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index b911d76dd66..00501c88420 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -1320,6 +1320,16 @@ On MIPS targets, set the @option{-mno-odd-spreg} option by default when using
 the o32 ABI.  This is normally used in conjunction with
 @option{--with-fp-32=64} in order to target the o32 FP64A ABI extension.
 
+@item --with-unfused-madd4
+On MIPS targets, set the @option{-munfused-madd4} option by default.
+On some platform, like Loongson 3A/3B 1000/2000/3000, madd.fmt/msub.fmt is
+broken, which may which may generate wrong calculator result.
+
+@item --without-unfused-madd4
+On MIPS targets, set the @option{-mno-unfused-madd4} option by default.
+On some platform, like Loongson 3A/3B 1000/2000/3000, madd.fmt/msub.fmt is
+broken, which may which may generate wrong calculator result.
+
 @item --with-nan=@var{encoding}
 On MIPS targets, set the default encoding convention to use for the
 special not-a-number (NaN) IEEE 754 floating-point data.  The
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 5c92fe69335..3ac80280eb8 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -862,6 +862,7 @@ Objective-C and Objective-C++ Dialects}.
 -mgp32  -mgp64  -mfp32  -mfpxx  -mfp64  -mhard-float  -msoft-float @gol
 -mno-float  -msingle-float  -mdouble-float @gol
 -modd-spreg -mno-odd-spreg @gol
+-munfused-madd4 -mno-unfused-madd4 @gol
 -mabs=@var{mode}  -mnan=@var{encoding} @gol
 -mdsp  -mno-dsp  -mdspr2  -mno-dspr2 @gol
 -mmcu -mmno-mcu @gol
@@ -19238,6 +19239,14 @@ for the o32 ABI.  This is the default for processors that are known to
 support these registers.  When using the o32 FPXX ABI, @option{-mno-odd-spreg}
 is set by default.
 
+@item -munfused-madd4
+@itemx -mno-unfused-madd4
+@opindex munfused-madd4
+@opindex munfused-madd4
+Enable or disable generate madd.fmt/msub.fmt instructions.
+On some platform, like Loongson 3A/3B 1000/2000/3000, madd.fmt/msub.fmt is
+broken, which may generate wrong calculator result.
+
 @item -mabs=2008
 @itemx -mabs=legacy
 @opindex mabs=2008