[PATCH] c++, v3: Change mangling of Intel/Motorola extended long double literals

[Jakub Jelinek]

On Wed, Sep 10, 2025 at 10:06:07AM +0200, Jason Merrill wrote:
> It looks like these tests won't run on m68k, can you make at least the -2
> test run (and pass) there?

Sure, tested there just with a cross (and only on those 2 new tests).

2025-09-10  Jakub Jelinek  <ja...@redhat.com>

        * mangle.cc (write_real_cst): Mangle Intel/Motorola extended
        80-bit formats using 20 hex digits instead of 24 or 32.

        * g++.target/i386/mangle-ldbl-1.C: New test.
        * g++.target/i386/mangle-ldbl-2.C: New test.
        * g++.target/m68k/mangle-ldbl-1.C: New test.
        * g++.target/m68k/mangle-ldbl-2.C: New test.

--- gcc/cp/mangle.cc.jj 2025-09-02 17:02:44.128176211 +0200
+++ gcc/cp/mangle.cc    2025-09-09 09:43:09.422358069 +0200
@@ -2190,6 +2190,29 @@ write_real_cst (const tree value)
   else
     i = words - 1, limit = -1, dir = -1;
 
+  if (GET_MODE_PRECISION (SCALAR_FLOAT_TYPE_MODE (type)) == 80
+      && abi_check (21))
+    {
+      /* For -fabi-version=21 and above mangle
+        Intel/Motorola extended format 1.0L as
+        3fff8000000000000000
+        rather than the previous
+        0000000000003fff8000000000000000 (x86_64)
+        00003fff8000000000000000 (ia32)
+        3fff00008000000000000000 (m68k -mc68020)
+        i.e. without any embedded padding bits.  */
+      if (words == 4)
+       i += dir;
+      else
+       gcc_assert (words == 3);
+      unsigned long val = (unsigned long) target_real[i];
+      if (REAL_MODE_FORMAT (SCALAR_FLOAT_TYPE_MODE (type))->signbit_ro == 95)
+       val >>= 16;
+      sprintf (buffer, "%04lx", val);
+      write_chars (buffer, 4);
+      i += dir;
+    }
+
   for (; i != limit; i += dir)
     {
       sprintf (buffer, "%08lx", (unsigned long) target_real[i]);
--- gcc/testsuite/g++.target/i386/mangle-ldbl-1.C.jj    2025-09-08 
19:34:51.143198289 +0200
+++ gcc/testsuite/g++.target/i386/mangle-ldbl-1.C       2025-09-08 
19:36:17.033063950 +0200
@@ -0,0 +1,8 @@
+// { dg-do compile { target { c++20 && { x86_64-*-linux* i?86-*-linux* } } } }
+// { dg-final { scan-assembler "_Z3fooILe3fff8000000000000000EEiv" } }
+// { dg-final { scan-assembler "_Z3fooILe40008000000000000000EEiv" } }
+
+template <long double a>
+int foo () { return 0; }
+
+int bar () { return foo <1.0L> () + foo <2.0L> (); }
--- gcc/testsuite/g++.target/i386/mangle-ldbl-2.C.jj    2025-09-08 
19:36:24.505965257 +0200
+++ gcc/testsuite/g++.target/i386/mangle-ldbl-2.C       2025-09-08 
19:38:56.977951557 +0200
@@ -0,0 +1,11 @@
+// { dg-do compile { target { c++20 && { x86_64-*-linux* i?86-*-linux* } } } }
+// { dg-additional-options "-fabi-version=20" }
+// { dg-final { scan-assembler "_Z3fooILe0000000000003fff8000000000000000EEiv" 
{ target { ! ia32 } } } }
+// { dg-final { scan-assembler "_Z3fooILe00000000000040008000000000000000EEiv" 
{ target { ! ia32 } } } }
+// { dg-final { scan-assembler "_Z3fooILe00003fff8000000000000000EEiv" { 
target ia32 } } }
+// { dg-final { scan-assembler "_Z3fooILe000040008000000000000000EEiv" { 
target ia32 } } }
+
+template <long double a>
+int foo () { return 0; }
+
+int bar () { return foo <1.0L> () + foo <2.0L> (); }
--- gcc/testsuite/g++.target/m68k/mangle-ldbl-1.C.jj    2025-09-09 
19:57:51.935990602 +0200
+++ gcc/testsuite/g++.target/m68k/mangle-ldbl-1.C       2025-09-10 
10:10:53.787463898 +0200
@@ -0,0 +1,9 @@
+// { dg-do compile { target { c++20 && { m68k*-*-linux* } } } }
+// { dg-additional-options "-m68020" }
+// { dg-final { scan-assembler "_Z3fooILe3fff8000000000000000EEiv" } }
+// { dg-final { scan-assembler "_Z3fooILe40008000000000000000EEiv" } }
+
+template <long double a>
+int foo () { return 0; }
+
+int bar () { return foo <1.0L> () + foo <2.0L> (); }
--- gcc/testsuite/g++.target/m68k/mangle-ldbl-2.C.jj    2025-09-09 
19:57:51.935990602 +0200
+++ gcc/testsuite/g++.target/m68k/mangle-ldbl-2.C       2025-09-10 
10:11:36.657880013 +0200
@@ -0,0 +1,9 @@
+// { dg-do compile { target { c++20 && { m68k*-*-linux* } } } }
+// { dg-additional-options "-m68020 -fabi-version=20" }
+// { dg-final { scan-assembler "_Z3fooILe3fff00008000000000000000EEiv" } }
+// { dg-final { scan-assembler "_Z3fooILe400000008000000000000000EEiv" } }
+
+template <long double a>
+int foo () { return 0; }
+
+int bar () { return foo <1.0L> () + foo <2.0L> (); }


        Jakub