[gdb/tdep] Fix PowerPC IEEE 128-bit format arg passing

On a powerpc system with gcc 12 built to default to 128-bit IEEE long double,
I run into:
...
(gdb) print find_max_long_double_real(4, ldc1, ldc2, ldc3, ldc4)^M
$8 = 0 + 0i^M
(gdb) FAIL: gdb.base/varargs.exp: print \
  find_max_long_double_real(4, ldc1, ldc2, ldc3, ldc4)
...

This is due to incorrect handling of the argument in ppc64_sysv_abi_push_param.

Fix this and similar cases, and expand the test-case to test handling of
homogeneous aggregates.

Tested on ppc64le-linux, power 10.

Co-Authored-By: Ulrich Weigand <uweigand@de.ibm.com>
Tested-by: Carl Love <cel@us.ibm.com>
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29543

3 files changed, 49 insertions, 6 deletions

diff --git a/gdb/ppc-sysv-tdep.c b/gdb/ppc-sysv-tdep.c
index 1fe81b9..78bb40e 100644
--- a/gdb/ppc-sysv-tdep.c
+++ b/gdb/ppc-sysv-tdep.c
@@ -1444,7 +1444,7 @@ ppc64_sysv_abi_push_param (struct gdbarch *gdbarch,
 	  == floatformats_ieee_quad))
     {
       /* IEEE FLOAT128, args in vector registers.  */
-      ppc64_sysv_abi_push_val (gdbarch, val, TYPE_LENGTH (type), 0, argpos);
+      ppc64_sysv_abi_push_val (gdbarch, val, TYPE_LENGTH (type), 16, argpos);
       ppc64_sysv_abi_push_vreg (gdbarch, val, argpos);
     }
   else if (type->code () == TYPE_CODE_FLT
@@ -1514,7 +1514,10 @@ ppc64_sysv_abi_push_param (struct gdbarch *gdbarch,
     }
   else
     {
-      ppc64_sysv_abi_push_val (gdbarch, val, TYPE_LENGTH (type), 0, argpos);
+      /* Align == 0 is correct for ppc64_sysv_abi_push_freg,
+	 Align == 16 is correct for ppc64_sysv_abi_push_vreg.
+	 Default to 0.	*/
+      int align = 0;
 
       /* The ABI (version 1.9) specifies that structs containing a
 	 single floating-point value, at any level of nesting of
@@ -1532,7 +1535,10 @@ ppc64_sysv_abi_push_param (struct gdbarch *gdbarch,
 	    if (TYPE_LENGTH (type) == 16
 		&& (gdbarch_long_double_format (gdbarch)
 		    == floatformats_ieee_quad))
-	      ppc64_sysv_abi_push_vreg (gdbarch, val, argpos);
+	      {
+		ppc64_sysv_abi_push_vreg (gdbarch, val, argpos);
+		align = 16;
+	      }
 	    else
 	      ppc64_sysv_abi_push_freg (gdbarch, type, val, argpos);
 	  }
@@ -1556,8 +1562,10 @@ ppc64_sysv_abi_push_param (struct gdbarch *gdbarch,
 		    && (gdbarch_long_double_format (gdbarch)
 			== floatformats_ieee_quad))
                  /* IEEE FLOAT128, args in vector registers.  */
-                 ppc64_sysv_abi_push_vreg (gdbarch, elval, argpos);
-
+		  {
+		    ppc64_sysv_abi_push_vreg (gdbarch, elval, argpos);
+		    align = 16;
+		  }
 		else if (eltype->code () == TYPE_CODE_FLT
                           || eltype->code () == TYPE_CODE_DECFLOAT)
 		    /* IBM long double and all other floats and decfloats, args
@@ -1567,9 +1575,14 @@ ppc64_sysv_abi_push_param (struct gdbarch *gdbarch,
 			 && eltype->is_vector ()
 			 && tdep->vector_abi == POWERPC_VEC_ALTIVEC
 			 && TYPE_LENGTH (eltype) == 16)
-		  ppc64_sysv_abi_push_vreg (gdbarch, elval, argpos);
+		  {
+		    ppc64_sysv_abi_push_vreg (gdbarch, elval, argpos);
+		    align = 16;
+		  }
 	      }
 	}
+
+      ppc64_sysv_abi_push_val (gdbarch, val, TYPE_LENGTH (type), align, argpos);
     }
 }
 
diff --git a/gdb/testsuite/gdb.base/varargs.c b/gdb/testsuite/gdb.base/varargs.c
index cacb29d..fcadcee 100644
--- a/gdb/testsuite/gdb.base/varargs.c
+++ b/gdb/testsuite/gdb.base/varargs.c
@@ -45,6 +45,16 @@ long double _Complex ldc2 = 2.0L + 2.0Li;
 long double _Complex ldc3 = 3.0L + 3.0Li;
 long double _Complex ldc4 = 4.0L + 4.0Li;
 
+struct sldc
+{
+  long double _Complex ldc;
+};
+
+struct sldc sldc1 = { 1.0L + 1.0Li };
+struct sldc sldc2 = { 2.0L + 2.0Li };
+struct sldc sldc3 = { 3.0L + 3.0Li };
+struct sldc sldc4 = { 4.0L + 4.0Li };
+
 #endif
 
 int
@@ -201,4 +211,22 @@ find_max_long_double_real (int num_vals, ...)
 }
 
 
+long double _Complex
+find_max_struct_long_double_real (int num_vals, ...)
+{
+  long double _Complex max = 0.0L + 0.0iL;
+  struct sldc x;
+  va_list argp;
+  int i;
+
+  va_start(argp, num_vals);
+  for (i = 0; i < num_vals; i++)
+    {
+      x = va_arg (argp, struct sldc);
+      if (creall (max) < creal (x.ldc)) max = x.ldc;
+    }
+
+  return max;
+}
+
 #endif /* TEST_COMPLEX */
diff --git a/gdb/testsuite/gdb.base/varargs.exp b/gdb/testsuite/gdb.base/varargs.exp
index 7bd2cb0..7fa464f 100644
--- a/gdb/testsuite/gdb.base/varargs.exp
+++ b/gdb/testsuite/gdb.base/varargs.exp
@@ -103,4 +103,6 @@ if [support_complex_tests] {
     set test "print find_max_long_double_real(4, ldc1, ldc2, ldc3, ldc4)"
     gdb_test $test ".*= 4 \\+ 4i"
 
+    set test "print find_max_struct_long_double_real(4, sldc1, sldc2, sldc3, sldc4)"
+    gdb_test $test ".*= 4 \\+ 4i"
 }