[Bug jit/64810] jit not working on armv7hl ("ld: error: /tmp/libgccjit-ZGemdr/fake.so uses VFP register arguments, /tmp/ccJFCBsE.o does not")

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64810

--- Comment #9 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Thanks Ramana.

I attempted a build of the jit with the configuration you suggested,
specifically:

  $ ../src/configure \
      --enable-host-shared \
      --enable-languages=jit,c++ \
      --disable-bootstrap \
      --enable-checking=release \
      --prefix=/home/dmalcolm/gcc-git-jit/install-jit \
      --with-arch=armv7-a \
      --with-float=hard \
      --with-fpu=vfpv3-d16

Unfortunately, I see the same failures.

Hacking in a "-v" into the driver invocation in jit-playback.c...

diff --git a/gcc/jit/jit-playback.c b/gcc/jit/jit-playback.c
index d2549a0..5f570a7 100644
--- a/gcc/jit/jit-playback.c
+++ b/gcc/jit/jit-playback.c
@@ -2271,6 +2271,8 @@ invoke_driver (const char *ctxt_progname,
      time.  */
   ADD_ARG ("-fno-use-linker-plugin");

+  ADD_ARG ("-v");
+
   /* pex argv arrays are NULL-terminated.  */
   ADD_ARG (NULL);

...I see that libgccjit attempts to invoke the driver to convert the .s
to a .so, but it fails like so:

Target: armv7l-unknown-linux-gnueabihf
Configured with: ../src/configure --enable-host-shared
--enable-languages=jit,c++ --disable-bootstrap --enable-checking=release
--prefix=/home/dmalcolm/gcc-git-jit/install-jit --with-arch=armv7-a
--with-float=hard --with-fpu=vfpv3-d16
Thread model: posix
gcc version 5.0.0 20150126 (experimental) (GCC)
COLLECT_GCC_OPTIONS='-shared' '-o' '/tmp/libgccjit-VxeXM1/fake.so'
'-fno-use-linker-plugin' '-v' '-march=armv7-a' '-mfloat-abi=hard'
'-mfpu=vfpv3-d16' '-mtls-dialect=gnu'
 as -v -march=armv7-a -mfloat-abi=hard -mfpu=vfpv3-d16 -meabi=5 -o
/tmp/ccCY7c5L.o /tmp/libgccjit-VxeXM1/fake.s
GNU assembler version 2.24 (armv7hl-redhat-linux-gnueabi) using BFD version
version 2.24
COMPILER_PATH=
LIBRARY_PATH=/home/dmalcolm/gcc-git-jit/build-jit-comment8/gcc/:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-shared' '-o' '/tmp/libgccjit-VxeXM1/fake.so'
'-fno-use-linker-plugin' '-v' '-march=armv7-a' '-mfloat-abi=hard'
'-mfpu=vfpv3-d16' '-mtls-dialect=gnu'
 ld --eh-frame-hdr -shared -dynamic-linker /lib/ld-linux-armhf.so.3 -X -m
armelf_linux_eabi -o /tmp/libgccjit-VxeXM1/fake.so /lib/crti.o
/home/dmalcolm/gcc-git-jit/build-jit-comment8/gcc/crtbeginS.o
-L/home/dmalcolm/gcc-git-jit/build-jit-comment8/gcc /tmp/ccCY7c5L.o -lgcc
--as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed
/home/dmalcolm/gcc-git-jit/build-jit-comment8/gcc/crtendS.o /lib/crtn.o
ld: error: /tmp/libgccjit-VxeXM1/fake.so uses VFP register arguments,
/tmp/ccCY7c5L.o does not
ld: failed to merge target specific data of file /tmp/ccCY7c5L.o

That said, with the "test-empty.c" testcase, the generated
"fake.s" looks like this:

        .cpu arm10tdmi
        .fpu softvfp
        .eabi_attribute 20, 1
        .eabi_attribute 21, 1
        .eabi_attribute 23, 3
        .eabi_attribute 24, 1
        .eabi_attribute 25, 1
        .eabi_attribute 26, 2
        .eabi_attribute 30, 2
        .eabi_attribute 34, 0
        .arm
        .syntax divided
        .file   "fake.c"
        .text
.Ltext0:
        .cfi_sections   .debug_frame
.Letext0:
        .section        .debug_line,"",%progbits
.Ldebug_line0:
        .section        .debug_str,"MS",%progbits,1
.LASF0:
        .ascii  "/tmp/libgccjit-La3Yzk/fake.c\000"
.LASF1:
        .ascii  "libgccjit 5.0.0 20150126 (experimental) -fPIC -O3 -"
        .ascii  "g --param ggc-min-expand=0 --param ggc-min-heapsize"
        .ascii  "=0\000"
        .ident  "GCC: (GNU) 5.0.0 20150126 (experimental)"
        .section        .note.GNU-stack,"",%progbits

In particular, I'm guessing that the line:
        .fpu softvfp
is at fault here.

This appears to come from arm.c:arm_file_start:
25689         if (TARGET_SOFT_FLOAT)
25690           {
25691             fpu_name = "softvfp";
25692           }
25693         else
and on debugging:
(gdb) p global_options.x_arm_float_abi
$1 = ARM_FLOAT_ABI_SOFT

Is this value bogus, given the configure-time options?

(if so, I'm guessing this is a jit-specific state-management issue)