[PATCH 1/3] Allow __ibm128 even if IEEE 128-bit floating point is not supported.

[Michael Meissner <meissner@linux.ibm.com>]

Allow __ibm128 even if IEEE 128-bit floating point is not supported.

This patch allows the use of the __ibm128 keyword on non-VSX systems.
Originally, the __ibm128 keyword was only enabled when the IEEE 128-bit
floating point is enabled.  Sometime back in the GCC 12 development period,
Segher asked that the __ibm128 keyword be allowed in older systems that don't
support IEEE 128-bit.  But at the time, stage 1 had closed for GCC 12, so I
deferred doing this change until GCC 13.  This patch allows __ibm128 to be used
if either IEEE 128-bit is enabled or long double used the IBM 128-bit format.

I have tested these patches on the following systems:

    1)	LE Power10 using --with-cpu=power10 --with-long-double-format=ieee
    2)	LE Power10 using --with-cpu=power9  --with-long-double-format=ibm
    3)	LE Power10 using --with-cpu=power8  --with-long-double-format=ibm
    4)	LE Power10 using --with-cpu=power10 --with-long-double-format=ibm
    5)	LE Power9  using --with-cpu=power9  --with-long-double-format=ibm
    6)	BE Power8  using --with-cpu=power8  --with-long-double-format=ibm
    7)	BE Power8  using --with-cpu=power5  --with-long-double-format=ibm

There were no regressions in the build or in the tests.

Can I check this patch into the trunk?

Did we want to backport this to earlier GCC releases?

2022-08-17   Michael Meissner  <meissner@linux.ibm.com>

gcc/

	* config/rs6000/rs6000-builtins.cc (rs6000_init_builtins): Enable using
	the__ibm128 keyword on systems that either use the 128-bit IBM long
	double format for long double or support IEEE 128-bit.
	* config/rs6000/rs6000.cc (rs6000_init_libfuncs): Create IBM 128-bit
	floating point support functions on systems that support the __ibm128
	keyword.
	(rs6000_scalar_mode_supported_p): Likewise.
	* config/rs6000/rs6000.h (TARGET_IBM128): New macro.
	* config/rs6000/rs6000.md (@extenddf<mode>2_fprs): Allow IFmode to be
	converted even if long double is not 128-bits.
	(extenddf<mode>2_vsx): Likewise.
	(extendiftf2):Allow conversion on systems that support the __ibm128
	keyword.
	(extendtfif2): Likewise.
	(trunciftf2): Likewise.
	(trunctfif2): Likewise.
---
 gcc/config/rs6000/rs6000-builtin.cc |  2 +-
 gcc/config/rs6000/rs6000.cc         | 13 ++++++++-----
 gcc/config/rs6000/rs6000.h          |  6 ++++++
 gcc/config/rs6000/rs6000.md         | 13 ++++++-------
 4 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/gcc/config/rs6000/rs6000-builtin.cc b/gcc/config/rs6000/rs6000-builtin.cc
index 12afa86854c..70680890415 100644
--- a/gcc/config/rs6000/rs6000-builtin.cc
+++ b/gcc/config/rs6000/rs6000-builtin.cc
@@ -713,7 +713,7 @@ rs6000_init_builtins (void)
      For IEEE 128-bit floating point, always create the type __ieee128.  If the
      user used -mfloat128, rs6000-c.cc will create a define from __float128 to
      __ieee128.  */
-  if (TARGET_LONG_DOUBLE_128 && (!TARGET_IEEEQUAD || TARGET_FLOAT128_TYPE))
+  if (TARGET_IBM128)
     {
       if (!TARGET_IEEEQUAD)
 	ibm128_float_type_node = long_double_type_node;
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index df491bee2ea..39527ce9bbc 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -11115,10 +11115,11 @@ rs6000_init_libfuncs (void)
 {
   /* __float128 support.  */
   if (TARGET_FLOAT128_TYPE)
-    {
-      init_float128_ibm (IFmode);
-      init_float128_ieee (KFmode);
-    }
+    init_float128_ieee (KFmode);
+
+  /* __ibm128 support.  */
+  if (TARGET_IBM128)
+    init_float128_ibm (IFmode);
 
   /* AIX/Darwin/64-bit Linux quad floating point routines.  */
   if (TARGET_LONG_DOUBLE_128)
@@ -23752,7 +23753,9 @@ rs6000_scalar_mode_supported_p (scalar_mode mode)
 
   if (DECIMAL_FLOAT_MODE_P (mode))
     return default_decimal_float_supported_p ();
-  else if (TARGET_FLOAT128_TYPE && (mode == KFmode || mode == IFmode))
+  else if (TARGET_FLOAT128_TYPE && mode == KFmode)
+    return true;
+  else if (TARGET_IBM128 && mode == IFmode)
     return true;
   else
     return default_scalar_mode_supported_p (mode);
diff --git a/gcc/config/rs6000/rs6000.h b/gcc/config/rs6000/rs6000.h
index ad9bf0f7358..813ec696c0d 100644
--- a/gcc/config/rs6000/rs6000.h
+++ b/gcc/config/rs6000/rs6000.h
@@ -564,6 +564,12 @@ extern int rs6000_vector_align[];
 					 && TARGET_P8_VECTOR		\
 					 && TARGET_POWERPC64)
 
+/* Whether the __ibm128 keyword is allowed.  Any system that supports _Float128
+   is assumed to be capable of supporting __ibm128.  Similarly if the long
+   double size is 128 bits, we assume __ibm128 is supported.  We don't want to
+   support it on a system without existing 128-bit long doubles.  */
+#define TARGET_IBM128	(TARGET_FLOAT128_TYPE || TARGET_LONG_DOUBLE_128)
+
 /* Inlining allows targets to define the meanings of bits in target_info
    field of ipa_fn_summary by itself, the used bits for rs6000 are listed
    below.  */
diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index 1367a2cb779..f942597c3b4 100644
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -8586,8 +8586,7 @@ (define_insn_and_split "@extenddf<mode>2_fprs"
 	(float_extend:IBM128
 	 (match_operand:DF 1 "nonimmediate_operand" "d,m,d")))
    (use (match_operand:DF 2 "nonimmediate_operand" "m,m,d"))]
-  "!TARGET_VSX && TARGET_HARD_FLOAT
-   && TARGET_LONG_DOUBLE_128 && FLOAT128_IBM_P (<MODE>mode)"
+  "!TARGET_VSX && TARGET_HARD_FLOAT && FLOAT128_IBM_P (<MODE>mode)"
   "#"
   "&& reload_completed"
   [(set (match_dup 3) (match_dup 1))
@@ -8604,7 +8603,7 @@ (define_insn_and_split "@extenddf<mode>2_vsx"
   [(set (match_operand:IBM128 0 "gpc_reg_operand" "=d,d")
 	(float_extend:IBM128
 	 (match_operand:DF 1 "nonimmediate_operand" "wa,m")))]
-  "TARGET_LONG_DOUBLE_128 && TARGET_VSX && FLOAT128_IBM_P (<MODE>mode)"
+  "TARGET_VSX && FLOAT128_IBM_P (<MODE>mode)"
   "#"
   "&& reload_completed"
   [(set (match_dup 2) (match_dup 1))
@@ -9061,7 +9060,7 @@ (define_insn "*ieee_128bit_vsx_nabs<mode>2_internal"
 (define_expand "extendiftf2"
   [(set (match_operand:TF 0 "gpc_reg_operand")
 	(float_extend:TF (match_operand:IF 1 "gpc_reg_operand")))]
-  "TARGET_FLOAT128_TYPE"
+  "TARGET_IBM128"
 {
   rs6000_expand_float128_convert (operands[0], operands[1], false);
   DONE;
@@ -9088,7 +9087,7 @@ (define_expand "extendtfkf2"
 (define_expand "extendtfif2"
   [(set (match_operand:IF 0 "gpc_reg_operand")
 	(float_extend:IF (match_operand:TF 1 "gpc_reg_operand")))]
-  "TARGET_FLOAT128_TYPE"
+  "TARGET_IBM128"
 {
   rs6000_expand_float128_convert (operands[0], operands[1], false);
   DONE;
@@ -9097,7 +9096,7 @@ (define_expand "extendtfif2"
 (define_expand "trunciftf2"
   [(set (match_operand:TF 0 "gpc_reg_operand")
 	(float_truncate:TF (match_operand:IF 1 "gpc_reg_operand")))]
-  "TARGET_FLOAT128_TYPE"
+  "TARGET_IBM128"
 {
   rs6000_expand_float128_convert (operands[0], operands[1], false);
   DONE;
@@ -9124,7 +9123,7 @@ (define_expand "trunckftf2"
 (define_expand "trunctfif2"
   [(set (match_operand:IF 0 "gpc_reg_operand")
 	(float_truncate:IF (match_operand:TF 1 "gpc_reg_operand")))]
-  "TARGET_FLOAT128_TYPE"
+  "TARGET_IBM128"
 {
   rs6000_expand_float128_convert (operands[0], operands[1], false);
   DONE;
-- 
2.37.2


-- 
Michael Meissner, IBM
PO Box 98, Ayer, Massachusetts, USA, 01432
email: meissner@linux.ibm.com