rs6000: Rework option -mpowerpc64 handling [PR106680]

PR106680 shows that -m32 -mpowerpc64 is different from
-mpowerpc64 -m32, this is determined by the way how we
handle option powerpc64 in rs6000_handle_option.

Segher pointed out this difference should be taken as
a bug and we should ensure that option powerpc64 is
independent of -m32/-m64.  So this patch removes the
handlings in rs6000_handle_option and add some necessary
supports in rs6000_option_override_internal instead.

With this patch, if users specify -m{no-,}powerpc64, the
specified value is honoured, otherwise, for 64bit it
always enables OPTION_MASK_POWERPC64; while for 32bit
and TARGET_POWERPC64 and OS_MISSING_POWERPC64, it disables
OPTION_MASK_POWERPC64.

btw, following Segher's suggestion, I did some tries to warn
when OPTION_MASK_POWERPC64 is set for OS_MISSING_POWERPC64.
If warn for the case that powerpc64 is specified explicitly,
there are some TCs using -m32 -mpowerpc64 on ppc64-linux,
they need some updates, meanwhile the artificial run
with "--target_board=unix'{-m32/-mpowerpc64}'" will have
noisy warnings on ppc64-linux.  If warn for the case that
it's specified implicitly, they can just be initialized by
TARGET_DEFAULT (like -m32 on ppc64-linux) or set from the
given cpu mask, we have to special case them and not to warn.
As Segher's latest comment, I decide not to warn them and
keep it consistent with before.

Bootstrapped and regress-tested on:
  - powerpc64-linux-gnu P7 and P8 {-m64,-m32}
  - powerpc64le-linux-gnu P9 and P10
  - powerpc-ibm-aix7.2.0.0 {-maix64,-maix32}
  - powerpc-darwin9 (with Iain's help)

	PR target/106680

gcc/ChangeLog:

	* common/config/rs6000/rs6000-common.cc (rs6000_handle_option): Remove
	the adjustment for option powerpc64 in -m64 handling, and remove the
	whole -m32 handling.
	* config/rs6000/rs6000.cc (rs6000_option_override_internal): When no
	explicit powerpc64 option is provided, enable it for -m64.  For 32 bit
	and OS_MISSING_POWERPC64, disable powerpc64 if it's enabled but not
	specified explicitly.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/pr106680-1.c: New test.
	* gcc.target/powerpc/pr106680-2.c: New test.
	* gcc.target/powerpc/pr106680-3.c: New test.
	* gcc.target/powerpc/pr106680-4.c: New test.

2022-12-27  Kewen Lin  <linkw@linux.ibm.com>
	    Iain Sandoe  <iain@sandoe.co.uk>

6 files changed, 85 insertions, 20 deletions

diff --git a/gcc/common/config/rs6000/rs6000-common.cc b/gcc/common/config/rs6000/rs6000-common.cc
index 8e393d0..c76b5c27 100644
--- a/gcc/common/config/rs6000/rs6000-common.cc
+++ b/gcc/common/config/rs6000/rs6000-common.cc
@@ -119,19 +119,8 @@ rs6000_handle_option (struct gcc_options *opts, struct gcc_options *opts_set,
 #else
     case OPT_m64:
 #endif
-      opts->x_rs6000_isa_flags |= OPTION_MASK_POWERPC64;
       opts->x_rs6000_isa_flags |= (~opts_set->x_rs6000_isa_flags
 				   & OPTION_MASK_PPC_GFXOPT);
-      opts_set->x_rs6000_isa_flags |= OPTION_MASK_POWERPC64;
-      break;
-
-#ifdef TARGET_USES_AIX64_OPT
-    case OPT_maix32:
-#else
-    case OPT_m32:
-#endif
-      opts->x_rs6000_isa_flags &= ~OPTION_MASK_POWERPC64;
-      opts_set->x_rs6000_isa_flags |= OPTION_MASK_POWERPC64;
       break;
 
     case OPT_mminimal_toc:
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 16ca456..6ac3adc 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -3645,17 +3645,12 @@ rs6000_option_override_internal (bool global_init_p)
       rs6000_pointer_size = 32;
     }
 
-  /* Some OSs don't support saving the high part of 64-bit registers on context
-     switch.  Other OSs don't support saving Altivec registers.  On those OSs,
-     we don't touch the OPTION_MASK_POWERPC64 or OPTION_MASK_ALTIVEC settings;
-     if the user wants either, the user must explicitly specify them and we
-     won't interfere with the user's specification.  */
+  /* Some OSs don't support saving Altivec registers.  On those OSs, we don't
+     touch the OPTION_MASK_ALTIVEC settings; if the user wants it, the user
+     must explicitly specify it and we won't interfere with the user's
+     specification.  */
 
   set_masks = POWERPC_MASKS;
-#ifdef OS_MISSING_POWERPC64
-  if (OS_MISSING_POWERPC64)
-    set_masks &= ~OPTION_MASK_POWERPC64;
-#endif
 #ifdef OS_MISSING_ALTIVEC
   if (OS_MISSING_ALTIVEC)
     set_masks &= ~(OPTION_MASK_ALTIVEC | OPTION_MASK_VSX
@@ -3665,6 +3660,18 @@ rs6000_option_override_internal (bool global_init_p)
   /* Don't override by the processor default if given explicitly.  */
   set_masks &= ~rs6000_isa_flags_explicit;
 
+  /* Without option powerpc64 specified explicitly, we need to ensure
+     powerpc64 always enabled for 64 bit here, otherwise some following
+     checks can use unexpected TARGET_POWERPC64 value.  Meanwhile, we
+     need to ensure set_masks doesn't have OPTION_MASK_POWERPC64 on,
+     otherwise later processing can clear it.  */
+  if (!(rs6000_isa_flags_explicit & OPTION_MASK_POWERPC64)
+      && TARGET_64BIT)
+    {
+      rs6000_isa_flags |= OPTION_MASK_POWERPC64;
+      set_masks &= ~OPTION_MASK_POWERPC64;
+    }
+
   /* Process the -mcpu=<xxx> and -mtune=<xxx> argument.  If the user changed
      the cpu in a target attribute or pragma, but did not specify a tuning
      option, use the cpu for the tuning option rather than the option specified
@@ -3715,6 +3722,18 @@ rs6000_option_override_internal (bool global_init_p)
       rs6000_isa_flags |= (flags & ~rs6000_isa_flags_explicit);
     }
 
+  /* Don't expect powerpc64 enabled on those OSes with OS_MISSING_POWERPC64,
+     since they do not save and restore the high half of the GPRs correctly
+     in all cases.  If the user explicitly specifies it, we won't interfere
+     with the user's specification.  */
+#ifdef OS_MISSING_POWERPC64
+  if (OS_MISSING_POWERPC64
+      && TARGET_32BIT
+      && TARGET_POWERPC64
+      && !(rs6000_isa_flags_explicit & OPTION_MASK_POWERPC64))
+    rs6000_isa_flags &= ~OPTION_MASK_POWERPC64;
+#endif
+
   if (rs6000_tune_index >= 0)
     tune_index = rs6000_tune_index;
   else if (cpu_index >= 0)
diff --git a/gcc/testsuite/gcc.target/powerpc/pr106680-1.c b/gcc/testsuite/gcc.target/powerpc/pr106680-1.c
new file mode 100644
index 0000000..d624d43
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr106680-1.c
@@ -0,0 +1,13 @@
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-mno-powerpc64" } */
+
+/* Verify there is an error message about PowerPC64 requirement.  */
+
+int foo ()
+{
+  return 1;
+}
+
+/* { dg-error "'-m64' requires a PowerPC64 cpu" "PR106680" { target powerpc*-*-linux* powerpc*-*-freebsd* powerpc-*-rtems* } 0 } */
+/* { dg-warning "'-m64' requires PowerPC64 architecture, enabling" "PR106680" { target powerpc*-*-darwin* } 0 } */
+/* { dg-warning "'-maix64' requires PowerPC64 architecture remain enabled" "PR106680" { target powerpc*-*-aix* } 0 } */
diff --git a/gcc/testsuite/gcc.target/powerpc/pr106680-2.c b/gcc/testsuite/gcc.target/powerpc/pr106680-2.c
new file mode 100644
index 0000000..a9ed737
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr106680-2.c
@@ -0,0 +1,14 @@
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-mno-powerpc64 -m64" } */
+
+/* Verify option -m64 doesn't override option -mno-powerpc64,
+   and there is an error message about PowerPC64 requirement.  */
+
+int foo ()
+{
+  return 1;
+}
+
+/* { dg-error "'-m64' requires a PowerPC64 cpu" "PR106680" { target powerpc*-*-linux* powerpc*-*-freebsd* powerpc-*-rtems* } 0 } */
+/* { dg-warning "'-m64' requires PowerPC64 architecture, enabling" "PR106680" { target powerpc*-*-darwin* } 0 } */
+/* { dg-warning "'-maix64' requires PowerPC64 architecture remain enabled" "PR106680" { target powerpc*-*-aix* } 0 } */
diff --git a/gcc/testsuite/gcc.target/powerpc/pr106680-3.c b/gcc/testsuite/gcc.target/powerpc/pr106680-3.c
new file mode 100644
index 0000000..b642d5c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr106680-3.c
@@ -0,0 +1,13 @@
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-m64 -mno-powerpc64" } */
+
+/* Verify there is an error message about PowerPC64 requirement.  */
+
+int foo ()
+{
+  return 1;
+}
+
+/* { dg-error "'-m64' requires a PowerPC64 cpu" "PR106680" { target powerpc*-*-linux* powerpc*-*-freebsd* powerpc-*-rtems* } 0 } */
+/* { dg-warning "'-m64' requires PowerPC64 architecture, enabling" "PR106680" { target powerpc*-*-darwin* } 0 } */
+/* { dg-warning "'-maix64' requires PowerPC64 architecture remain enabled" "PR106680" { target powerpc*-*-aix* } 0 } */
diff --git a/gcc/testsuite/gcc.target/powerpc/pr106680-4.c b/gcc/testsuite/gcc.target/powerpc/pr106680-4.c
new file mode 100644
index 0000000..7fee48d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr106680-4.c
@@ -0,0 +1,17 @@
+/* Skip this on aix, otherwise it emits the error message like "64-bit
+   computation with 32-bit addressing not yet supported" on aix.  */
+/* { dg-skip-if "" { powerpc*-*-aix* } } */
+/* { dg-require-effective-target ilp32 } */
+/* { dg-options "-mpowerpc64 -m32 -O2" } */
+
+/* Verify option -m32 doesn't override option -mpowerpc64.
+   If option -mpowerpc64 gets overridden, the assembly would
+   end up with addc and adde.  */
+/* { dg-final { scan-assembler-not {\maddc\M} } } */
+/* { dg-final { scan-assembler-not {\madde\M} } } */
+/* { dg-final { scan-assembler-times {\madd\M} 1 } } */
+
+long long foo (long long a, long long b)
+{
+  return a+b;
+}