i386: Access external function via GOT slot for -fno-plt

i386 psABI has been updated to clarify that R_386_GOT32X and R_386_GOT32
relocations can be used to access GOT without base register when PIC is
disabled:

https://groups.google.com/forum/#!topic/ia32-abi/awsRSvJOJfs

32-bit x86 assembler and linker from binutils 2.26.1 and 2.27 support

call/jmp *_start@GOT
cmpl $0, bar@GOT

for both normal and IFUNC functions.  We check if 32-bit x86 assembler
and linker have the fix for:

https://sourceware.org/bugzilla/show_bug.cgi?id=20244

before accessing external function via GOT slot for -fno-plt in both PIC
and non-PIC modes.

	PR target/66232
	PR target/67400
	* configure.ac (as_ix86_tls_ldm_opt): Renamed to ...
	(as_ix86_gas_32_opt): This.
	(ld_ix86_tls_ldm_opt): Renamed to ...
	(ld_ix86_gld_32_opt): This.
	(R_386_TLS_LDM reloc): Updated.
	(R_386_GOT32X reloc): New assembler/linker check.
	(HAVE_AS_IX86_GOT32X): New.  Defined to 1 if 32-bit assembler and
	linker support "jmp *_start@GOT" and "cmpl $0, bar@GOT".  Otherise,
	defined to 0.
	* config.in: Regenerated.
	* configure: Likewise.
	* config/i386/i386.c (ix86_force_load_from_GOT_p): Return
	true if HAVE_AS_IX86_GOT32X is 1 in 32-bit mode.
	(ix86_legitimate_address_p): Allow UNSPEC_GOT for -fno-plt
	if ix86_force_load_from_GOT_p returns true.
	(ix86_print_operand_address_as): Also support UNSPEC_GOT if
	ix86_force_load_from_GOT_p returns true.
	(ix86_expand_move): Generate UNSPEC_GOT in 32-bit mode to load
	the external function address via the GOT slot.
	(ix86_nopic_noplt_attribute_p): Check both TARGET_64BIT and
	HAVE_AS_IX86_GOT32X before returning false.
	(ix86_output_call_insn): Generate "%!jmp/call\t*%p0@GOT" in
	32-bit mode if ix86_nopic_noplt_attribute_p returns true.

gcc/testsuite/

	PR target/66232
	PR target/67400
	* gcc.target/i386/pr66232-14.c: New file.
	* gcc.target/i386/pr66232-15.c: Likewise.
	* gcc.target/i386/pr66232-16.c: Likewise.
	* gcc.target/i386/pr66232-17.c: Likewise.
	* gcc.target/i386/pr67400-1.c: Don't disable for ia32.  Scan for
	ia32 if R_386_GOT32X relocation is supported.
	* gcc.target/i386/pr67400-2.c: Likewise.
	* gcc.target/i386/pr67400-3.c: Likewise.
	* gcc.target/i386/pr67400-4.c: Likewise.
	* gcc.target/i386/pr67400-6.c: Likewise.
	* gcc.target/i386/pr67400-7.c: Likewise.
	* lib/target-supports.exp (check_effective_target_got32x_reloc):
	New.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@237736 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 36 insertions, 15 deletions

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 9c7b015e9c8..f7944f994eb 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -15125,7 +15125,8 @@ darwin_local_data_pic (rtx disp)
 bool
 ix86_force_load_from_GOT_p (rtx x)
 {
-  return (TARGET_64BIT && !TARGET_PECOFF && !TARGET_MACHO
+  return ((TARGET_64BIT || HAVE_AS_IX86_GOT32X)
+	  && !TARGET_PECOFF && !TARGET_MACHO
 	  && !flag_plt && !flag_pic
 	  && ix86_cmodel != CM_LARGE
 	  && GET_CODE (x) == SYMBOL_REF
@@ -15602,10 +15603,16 @@ ix86_legitimate_address_p (machine_mode, rtx addr, bool strict)
 	  && XINT (XEXP (disp, 0), 1) != UNSPEC_MACHOPIC_OFFSET)
 	switch (XINT (XEXP (disp, 0), 1))
 	  {
-	  /* Refuse GOTOFF and GOT in 64bit mode since it is always 64bit when
-	     used.  While ABI specify also 32bit relocations, we don't produce
-	     them at all and use IP relative instead.  */
+	  /* Refuse GOTOFF and GOT in 64bit mode since it is always 64bit
+	     when used.  While ABI specify also 32bit relocations, we
+	     don't produce them at all and use IP relative instead.
+	     Allow GOT in 32bit mode for both PIC and non-PIC if symbol
+	     should be loaded via GOT.  */
 	  case UNSPEC_GOT:
+	    if (!TARGET_64BIT
+		&& ix86_force_load_from_GOT_p (XVECEXP (XEXP (disp, 0), 0, 0)))
+	      goto is_legitimate_pic;
+	    /* FALLTHRU */
 	  case UNSPEC_GOTOFF:
 	    gcc_assert (flag_pic);
 	    if (!TARGET_64BIT)
@@ -18194,7 +18201,8 @@ ix86_print_operand_address_as (FILE *file, rtx addr,
       /* Load the external function address via the GOT slot to avoid PLT.  */
       else if (GET_CODE (disp) == CONST
 	       && GET_CODE (XEXP (disp, 0)) == UNSPEC
-	       && XINT (XEXP (disp, 0), 1) == UNSPEC_GOTPCREL
+	       && (XINT (XEXP (disp, 0), 1) == UNSPEC_GOTPCREL
+		   || XINT (XEXP (disp, 0), 1) == UNSPEC_GOT)
 	       && ix86_force_load_from_GOT_p (XVECEXP (XEXP (disp, 0), 0, 0)))
 	output_pic_addr_const (file, disp, 0);
       else if (flag_pic)
@@ -19449,7 +19457,9 @@ ix86_expand_move (machine_mode mode, rtx operands[])
 	{
 	  /* Load the external function address via GOT slot to avoid PLT.  */
 	  op1 = gen_rtx_UNSPEC (Pmode, gen_rtvec (1, op1),
-				UNSPEC_GOTPCREL);
+				(TARGET_64BIT
+				 ? UNSPEC_GOTPCREL
+				 : UNSPEC_GOT));
 	  op1 = gen_rtx_CONST (Pmode, op1);
 	  op1 = gen_const_mem (Pmode, op1);
 	  set_mem_alias_set (op1, ix86_GOT_alias_set ());
@@ -28016,18 +28026,19 @@ ix86_expand_call (rtx retval, rtx fnaddr, rtx callarg1,
   return call;
 }
 
-/* Return true if the function being called was marked with attribute "noplt"
-   or using -fno-plt and we are compiling for non-PIC and x86_64.  We need to
-   handle the non-PIC case in the backend because there is no easy interface
-   for the front-end to force non-PLT calls to use the GOT.  This is currently
-   used only with 64-bit ELF targets to call the function marked "noplt"
-   indirectly.  */
+/* Return true if the function being called was marked with attribute
+   "noplt" or using -fno-plt and we are compiling for non-PIC.  We need
+   to handle the non-PIC case in the backend because there is no easy
+   interface for the front-end to force non-PLT calls to use the GOT.
+   This is currently used only with 64-bit or 32-bit GOT32X ELF targets
+   to call the function marked "noplt" indirectly.  */
 
 static bool
 ix86_nopic_noplt_attribute_p (rtx call_op)
 {
   if (flag_pic || ix86_cmodel == CM_LARGE
-      || !TARGET_64BIT || TARGET_MACHO || TARGET_SEH || TARGET_PECOFF
+      || !(TARGET_64BIT || HAVE_AS_IX86_GOT32X)
+      || TARGET_MACHO || TARGET_SEH || TARGET_PECOFF
       || SYMBOL_REF_LOCAL_P (call_op))
     return false;
 
@@ -28055,7 +28066,12 @@ ix86_output_call_insn (rtx_insn *insn, rtx call_op)
       if (direct_p)
 	{
 	  if (ix86_nopic_noplt_attribute_p (call_op))
-	    xasm = "%!jmp\t{*%p0@GOTPCREL(%%rip)|[QWORD PTR %p0@GOTPCREL[rip]]}";
+	    {
+	      if (TARGET_64BIT)
+		xasm = "%!jmp\t{*%p0@GOTPCREL(%%rip)|[QWORD PTR %p0@GOTPCREL[rip]]}";
+	      else
+		xasm = "%!jmp\t{*%p0@GOT|[DWORD PTR %p0@GOT]}";
+	    }
 	  else
 	    xasm = "%!jmp\t%P0";
 	}
@@ -28103,7 +28119,12 @@ ix86_output_call_insn (rtx_insn *insn, rtx call_op)
   if (direct_p)
     {
       if (ix86_nopic_noplt_attribute_p (call_op))
-	xasm = "%!call\t{*%p0@GOTPCREL(%%rip)|[QWORD PTR %p0@GOTPCREL[rip]]}";
+	{
+	  if (TARGET_64BIT)
+	    xasm = "%!call\t{*%p0@GOTPCREL(%%rip)|[QWORD PTR %p0@GOTPCREL[rip]]}";
+	  else
+	    xasm = "%!call\t{*%p0@GOT|[DWORD PTR %p0@GOT]}";
+	}
       else
 	xasm = "%!call\t%P0";
     }