https://gcc.gnu.org/g:2dfff4ffe88c9ef4f7c7887c09e5cee171b1a17e
commit r16-3736-g2dfff4ffe88c9ef4f7c7887c09e5cee171b1a17e
Author: Jakub Jelinek <ja...@redhat.com>
Date: Wed Sep 10 10:48:31 2025 +0200
c++: Change mangling of Intel/Motorola extended long double literals
On Fri, Sep 05, 2025 at 09:57:06PM +0200, Matthias Kretz wrote:
> > Hmm, would this fail for x86 long double, which is 80 bits? OK, just
> > checked. It's mangled as 12/16 bytes on i686/x86_64.
>
> It seems that Clang and GCC disagree on mangling 80-Bit long double:
>
> I like Clang's interpretation of
https://itanium-cxx-abi.github.io/cxx-abi/
> abi.html#mangle.float better.
This patch changes the mangling of 80-bit long double literals from
24 or 32 digits (on m68k with padding bits in the middle, on x86
at the start) to just 20 hex digits.
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.
Diff:
---
gcc/cp/mangle.cc | 23 +++++++++++++++++++++++
gcc/testsuite/g++.target/i386/mangle-ldbl-1.C | 8 ++++++++
gcc/testsuite/g++.target/i386/mangle-ldbl-2.C | 11 +++++++++++
gcc/testsuite/g++.target/m68k/mangle-ldbl-1.C | 9 +++++++++
gcc/testsuite/g++.target/m68k/mangle-ldbl-2.C | 9 +++++++++
5 files changed, 60 insertions(+)
diff --git a/gcc/cp/mangle.cc b/gcc/cp/mangle.cc
index c1aae2de52b0..7678c0a97b96 100644
--- a/gcc/cp/mangle.cc
+++ b/gcc/cp/mangle.cc
@@ -2203,6 +2203,29 @@ 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]);
diff --git a/gcc/testsuite/g++.target/i386/mangle-ldbl-1.C
b/gcc/testsuite/g++.target/i386/mangle-ldbl-1.C
new file mode 100644
index 000000000000..c891e9532474
--- /dev/null
+++ b/gcc/testsuite/g++.target/i386/mangle-ldbl-1.C
@@ -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> (); }
diff --git a/gcc/testsuite/g++.target/i386/mangle-ldbl-2.C
b/gcc/testsuite/g++.target/i386/mangle-ldbl-2.C
new file mode 100644
index 000000000000..baef12e15d22
--- /dev/null
+++ b/gcc/testsuite/g++.target/i386/mangle-ldbl-2.C
@@ -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> (); }
diff --git a/gcc/testsuite/g++.target/m68k/mangle-ldbl-1.C
b/gcc/testsuite/g++.target/m68k/mangle-ldbl-1.C
new file mode 100644
index 000000000000..2a473ae2a66d
--- /dev/null
+++ b/gcc/testsuite/g++.target/m68k/mangle-ldbl-1.C
@@ -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> (); }
diff --git a/gcc/testsuite/g++.target/m68k/mangle-ldbl-2.C
b/gcc/testsuite/g++.target/m68k/mangle-ldbl-2.C
new file mode 100644
index 000000000000..113775e87880
--- /dev/null
+++ b/gcc/testsuite/g++.target/m68k/mangle-ldbl-2.C
@@ -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> (); }
