re PR target/71806 (PowerPC -mcpu=power9 enables __float128 without an explicit -mfloat128)

[gcc]
2016-07-08  Michael Meissner  <meissner@linux.vnet.ibm.com>

	PR target/71806
	* config/rs6000/rs6000-cpus.def (ISA_3_0_MASKS_SERVER): Do not
	enable -mfloat128-hardware by default.
	(ISA_3_0_MASKS_IEEE): New macro to give all of the VSX options
	that IEEE 128-bit hardware support needs.
	* config/rs6000/rs6000.c (rs6000_option_override_internal): If
	-mcpu=power9 -mfloat128, enable -mfloat128-hardware by default.
	Use ISA_3_0_MASKS_IEEE as the set of options that IEEE 128-bit
	floating point requires.
	* doc/invoke.texi (RS/6000 and PowerPC Options): Document
	-mfloat128 and -mfloat128-hardware changes.

[gcc/testsuite]
2016-07-08  Michael Meissner  <meissner@linux.vnet.ibm.com>

	PR target/71806
	* gcc.target/powerpc/p9-lxvx-stxvx-3.c: Add -mfloat128 option.

From-SVN: r238164

6 files changed, 57 insertions, 13 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index dc648ca..e2711cc 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,17 @@
+2016-07-08  Michael Meissner  <meissner@linux.vnet.ibm.com>
+
+	PR target/71806
+	* config/rs6000/rs6000-cpus.def (ISA_3_0_MASKS_SERVER): Do not
+	enable -mfloat128-hardware by default.
+	(ISA_3_0_MASKS_IEEE): New macro to give all of the VSX options
+	that IEEE 128-bit hardware support needs.
+	* config/rs6000/rs6000.c (rs6000_option_override_internal): If
+	-mcpu=power9 -mfloat128, enable -mfloat128-hardware by default.
+	Use ISA_3_0_MASKS_IEEE as the set of options that IEEE 128-bit
+	floating point requires.
+	* doc/invoke.texi (RS/6000 and PowerPC Options): Document
+	-mfloat128 and -mfloat128-hardware changes.
+
 2016-07-08  Alan Hayward  <alan.hayward@arm.com>
 
 	PR tree-optimization/71667
diff --git a/gcc/config/rs6000/rs6000-cpus.def b/gcc/config/rs6000/rs6000-cpus.def
index 7c67b6f..401088f 100644
--- a/gcc/config/rs6000/rs6000-cpus.def
+++ b/gcc/config/rs6000/rs6000-cpus.def
@@ -61,9 +61,9 @@
 				 | OPTION_MASK_UPPER_REGS_SF)
 
 /* Add ISEL back into ISA 3.0, since it is supposed to be a win.  Do not add
-   P9_MINMAX until the hardware that supports it is available.  */
+   P9_MINMAX until the hardware that supports it is available.  Do not add
+   FLOAT128_HW here until we are ready to make -mfloat128 on by default.  */
 #define ISA_3_0_MASKS_SERVER	(ISA_2_7_MASKS_SERVER			\
-				 | OPTION_MASK_FLOAT128_HW		\
 				 | OPTION_MASK_ISEL			\
 				 | OPTION_MASK_MODULO			\
 				 | OPTION_MASK_P9_FUSION		\
@@ -72,6 +72,16 @@
 				 | OPTION_MASK_P9_MISC			\
 				 | OPTION_MASK_P9_VECTOR)
 
+/* Support for the IEEE 128-bit floating point hardware requires a lot of the
+   VSX instructions that are part of ISA 3.0.  */
+#define ISA_3_0_MASKS_IEEE	(OPTION_MASK_VSX			\
+				 | OPTION_MASK_P8_VECTOR		\
+				 | OPTION_MASK_P9_VECTOR		\
+				 | OPTION_MASK_DIRECT_MOVE		\
+				 | OPTION_MASK_UPPER_REGS_DI		\
+				 | OPTION_MASK_UPPER_REGS_DF		\
+				 | OPTION_MASK_UPPER_REGS_SF)
+
 #define POWERPC_7400_MASK	(OPTION_MASK_PPC_GFXOPT | OPTION_MASK_ALTIVEC)
 
 /* Deal with ports that do not have -mstrict-align.  */
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index d2a62bd..99a2e36 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -4381,14 +4381,21 @@ rs6000_option_override_internal (bool global_init_p)
       rs6000_isa_flags &= ~(OPTION_MASK_FLOAT128 | OPTION_MASK_FLOAT128_HW);
     }
 
+  /* If we have -mfloat128 and full ISA 3.0 support, enable -mfloat128-hardware
+     by default.  */
+  if (TARGET_FLOAT128 && !TARGET_FLOAT128_HW
+      && (rs6000_isa_flags & ISA_3_0_MASKS_IEEE) == ISA_3_0_MASKS_IEEE
+      && !(rs6000_isa_flags_explicit & OPTION_MASK_FLOAT128_HW))
+    {
+      rs6000_isa_flags |= OPTION_MASK_FLOAT128_HW;
+      if ((rs6000_isa_flags & OPTION_MASK_FLOAT128) != 0)
+	rs6000_isa_flags_explicit |= OPTION_MASK_FLOAT128_HW;
+    }
+
   /* IEEE 128-bit floating point hardware instructions imply enabling
      __float128.  */
   if (TARGET_FLOAT128_HW
-      && (rs6000_isa_flags & (OPTION_MASK_P9_VECTOR
-			      | OPTION_MASK_DIRECT_MOVE
-			      | OPTION_MASK_UPPER_REGS_DI
-			      | OPTION_MASK_UPPER_REGS_DF
-			      | OPTION_MASK_UPPER_REGS_SF)) == 0)
+      && (rs6000_isa_flags & ISA_3_0_MASKS_IEEE) != ISA_3_0_MASKS_IEEE)
     {
       if ((rs6000_isa_flags_explicit & OPTION_MASK_FLOAT128_HW) != 0)
 	error ("-mfloat128-hardware requires full ISA 3.0 support");
@@ -4396,10 +4403,6 @@ rs6000_option_override_internal (bool global_init_p)
       rs6000_isa_flags &= ~OPTION_MASK_FLOAT128_HW;
     }
 
-  else if (TARGET_P9_VECTOR && !TARGET_FLOAT128_HW
-	   && (rs6000_isa_flags_explicit & OPTION_MASK_FLOAT128_HW) == 0)
-    rs6000_isa_flags |= OPTION_MASK_FLOAT128_HW;
-
   if (TARGET_FLOAT128_HW
       && (rs6000_isa_flags_explicit & OPTION_MASK_FLOAT128) == 0)
     rs6000_isa_flags |= OPTION_MASK_FLOAT128;
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index b6398ff..e185178 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -20355,9 +20355,14 @@ hardware instructions.
 
 The VSX instruction set (@option{-mvsx}, @option{-mcpu=power7}, or
 @option{-mcpu=power8}) must be enabled to use the @option{-mfloat128}
-option.  The @code{-mfloat128} option only works on PowerPC 64-bit
+option.  The @option{-mfloat128} option only works on PowerPC 64-bit
 Linux systems.
 
+If you use the ISA 3.0 instruction set (@option{-mcpu=power9}), the
+@option{-mfloat128} option will also enable the generation of ISA 3.0
+IEEE 128-bit floating point instructions.  Otherwise, IEEE 128-bit
+floating point will be done with software emulation.
+
 @item -mfloat128-hardware
 @itemx -mno-float128-hardware
 @opindex mfloat128-hardware
@@ -20365,6 +20370,13 @@ Linux systems.
 Enable/disable using ISA 3.0 hardware instructions to support the
 @var{__float128} data type.
 
+If you use @option{-mfloat128-hardware}, it will enable the option
+@option{-mfloat128} as well.
+
+If you select ISA 3.0 instructions with @option{-mcpu=power9}, but do
+not use either @option{-mfloat128} or @option{-mfloat128-hardware},
+the IEEE 128-bit floating point support will not be enabled.
+
 @item -mmodulo
 @itemx -mno-modulo
 @opindex mmodulo
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3af679a..ab2537f 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-07-08  Michael Meissner  <meissner@linux.vnet.ibm.com>
+
+	PR target/71806
+	* gcc.target/powerpc/p9-lxvx-stxvx-3.c: Add -mfloat128 option.
+
 2016-07-08  Alan Hayward  <alan.hayward@arm.com>
 
 	PR tree-optimization/71667
diff --git a/gcc/testsuite/gcc.target/powerpc/p9-lxvx-stxvx-3.c b/gcc/testsuite/gcc.target/powerpc/p9-lxvx-stxvx-3.c
index 4947386..b8a03d3 100644
--- a/gcc/testsuite/gcc.target/powerpc/p9-lxvx-stxvx-3.c
+++ b/gcc/testsuite/gcc.target/powerpc/p9-lxvx-stxvx-3.c
@@ -1,6 +1,6 @@
 /* { dg-do compile { target { powerpc64le-*-* } } } */
 /* { dg-skip-if "do not override -mcpu" { powerpc*-*-* } { "-mcpu=*" } { "-mcpu=power9" } } */
-/* { dg-options "-mcpu=power9 -O3" } */
+/* { dg-options "-mcpu=power9 -O3 -mfloat128" } */
 /* { dg-require-effective-target powerpc_p9vector_ok } */
 /* { dg-final { scan-assembler "lxvx" } } */
 /* { dg-final { scan-assembler "stxvx" } } */