rs6000: Only enable PCREL on supported ABIs [PR111045]

PCREL data accesses are only officially supported on ELFv2.  We currently
incorrectly enable PCREL on all Power10 compiles in which prefix instructions
are also enabled.  Rework the option override code so we only enable PCREL
for those ABIs that actually support it.

Jeevitha has confirmed this patch fixes the testsuite fallout seen with her
PR110320 patch.

This has been bootstrapped and regtested with no regressions on the following
builds: powerpc64le-linux, powerpc64le-linux --with-cpu=power10 and
powerpc64-linux - testsuite run in both 32-bit and 64-bit modes.
Ok for trunk?

Ok for the release branches after some burn-in on trunk?

Peter


gcc/
	PR target/111045
	* config/rs6000/linux64.h (PCREL_SUPPORTED_BY_OS): Only test the ABI.
	* config/rs6000/rs6000-cpus.def (RS6000_CPU): Remove OPTION_MASK_PCREL
	from power10.
	* config/rs6000/predicates.md: Use TARGET_PCREL.
	* config/rs6000/rs6000-logue.cc (rs6000_decl_ok_for_sibcall): Likewise.
	(rs6000_global_entry_point_prologue_needed_p): Likewise.
	(rs6000_output_function_prologue): Likewise.
	* config/rs6000/rs6000.md: Likewise.
	* config/rs6000/rs6000.cc (rs6000_option_override_internal): Rework
	the logic for enabling PCREL by default.
	(rs6000_legitimize_tls_address): Use TARGET_PCREL.
	(rs6000_call_template_1): Likewise.
	(rs6000_indirect_call_template_1): Likewise.
	(rs6000_longcall_ref): Likewise.
	(rs6000_call_aix): Likewise.
	(rs6000_sibcall_aix): Likewise.
	(rs6000_pcrel_p): Remove.
	* config/rs6000/rs6000-protos.h (rs6000_pcrel_p): Likewise.

gcc/testsuite/
	PR target/111045
	* gcc.target/powerpc/pr111045.c: New test.
	* gcc.target/powerpc/float128-constant.c: Add instruction counts for
	non-pcrel compiles.

Hi,

on 2023/11/15 11:01, Peter Bergner wrote:
> PCREL data accesses are only officially supported on ELFv2.  We currently
> incorrectly enable PCREL on all Power10 compiles in which prefix instructions
> are also enabled.  Rework the option override code so we only enable PCREL
> for those ABIs that actually support it.
> 
> Jeevitha has confirmed this patch fixes the testsuite fallout seen with her
> PR110320 patch.
> 
> This has been bootstrapped and regtested with no regressions on the following
> builds: powerpc64le-linux, powerpc64le-linux --with-cpu=power10 and
> powerpc64-linux - testsuite run in both 32-bit and 64-bit modes.
> Ok for trunk?

OK for trunk and backporting, but wait for two days or so in case Segher and
David have some comments, thanks!

BR,
Kewen

> 
> Ok for the release branches after some burn-in on trunk?
> 
> Peter
> 
> 
> gcc/
> 	PR target/111045
> 	* config/rs6000/linux64.h (PCREL_SUPPORTED_BY_OS): Only test the ABI.
> 	* config/rs6000/rs6000-cpus.def (RS6000_CPU): Remove OPTION_MASK_PCREL
> 	from power10.
> 	* config/rs6000/predicates.md: Use TARGET_PCREL.
> 	* config/rs6000/rs6000-logue.cc (rs6000_decl_ok_for_sibcall): Likewise.
> 	(rs6000_global_entry_point_prologue_needed_p): Likewise.
> 	(rs6000_output_function_prologue): Likewise.
> 	* config/rs6000/rs6000.md: Likewise.
> 	* config/rs6000/rs6000.cc (rs6000_option_override_internal): Rework
> 	the logic for enabling PCREL by default.
> 	(rs6000_legitimize_tls_address): Use TARGET_PCREL.
> 	(rs6000_call_template_1): Likewise.
> 	(rs6000_indirect_call_template_1): Likewise.
> 	(rs6000_longcall_ref): Likewise.
> 	(rs6000_call_aix): Likewise.
> 	(rs6000_sibcall_aix): Likewise.
> 	(rs6000_pcrel_p): Remove.
> 	* config/rs6000/rs6000-protos.h (rs6000_pcrel_p): Likewise.
> 
> gcc/testsuite/
> 	PR target/111045
> 	* gcc.target/powerpc/pr111045.c: New test.
> 	* gcc.target/powerpc/float128-constant.c: Add instruction counts for
> 	non-pcrel compiles.
> 
> diff --git a/gcc/config/rs6000/linux64.h b/gcc/config/rs6000/linux64.h
> index 98b7255c95f..5b77bd7fd51 100644
> --- a/gcc/config/rs6000/linux64.h
> +++ b/gcc/config/rs6000/linux64.h
> @@ -563,8 +563,5 @@ extern int dot_symbols;
>  #define TARGET_FLOAT128_ENABLE_TYPE 1
>  
>  /* Enable using prefixed PC-relative addressing on POWER10 if the ABI
> -   supports it.  The ELF v2 ABI only supports PC-relative relocations for
> -   the medium code model.  */
> -#define PCREL_SUPPORTED_BY_OS	(TARGET_POWER10 && TARGET_PREFIXED	\
> -				 && ELFv2_ABI_CHECK			\
> -				 && TARGET_CMODEL == CMODEL_MEDIUM)
> +   supports it.  */
> +#define PCREL_SUPPORTED_BY_OS	(ELFv2_ABI_CHECK)
> diff --git a/gcc/config/rs6000/rs6000-cpus.def b/gcc/config/rs6000/rs6000-cpus.def
> index 4f350da378c..fe01a2312ae 100644
> --- a/gcc/config/rs6000/rs6000-cpus.def
> +++ b/gcc/config/rs6000/rs6000-cpus.def
> @@ -256,7 +256,8 @@ RS6000_CPU ("power8", PROCESSOR_POWER8, MASK_POWERPC64 | ISA_2_7_MASKS_SERVER
>  	    | OPTION_MASK_HTM)
>  RS6000_CPU ("power9", PROCESSOR_POWER9, MASK_POWERPC64 | ISA_3_0_MASKS_SERVER
>  	    | OPTION_MASK_HTM)
> -RS6000_CPU ("power10", PROCESSOR_POWER10, MASK_POWERPC64 | ISA_3_1_MASKS_SERVER)
> +RS6000_CPU ("power10", PROCESSOR_POWER10, MASK_POWERPC64
> +	    | (ISA_3_1_MASKS_SERVER & ~OPTION_MASK_PCREL))
>  RS6000_CPU ("powerpc", PROCESSOR_POWERPC, 0)
>  RS6000_CPU ("powerpc64", PROCESSOR_POWERPC64, OPTION_MASK_PPC_GFXOPT
>  	    | MASK_POWERPC64)
> diff --git a/gcc/config/rs6000/predicates.md b/gcc/config/rs6000/predicates.md
> index ef7d3f214c4..0b76541fc0a 100644
> --- a/gcc/config/rs6000/predicates.md
> +++ b/gcc/config/rs6000/predicates.md
> @@ -1216,7 +1216,7 @@
>  			 && SYMBOL_REF_DECL (op) != NULL
>  			 && TREE_CODE (SYMBOL_REF_DECL (op)) == FUNCTION_DECL
>  			 && (rs6000_fndecl_pcrel_p (SYMBOL_REF_DECL (op))
> -			     != rs6000_pcrel_p ()))")))
> +			     != TARGET_PCREL))")))
>  
>  ;; Return 1 if this operand is a valid input for a move insn.
>  (define_predicate "input_operand"
> diff --git a/gcc/config/rs6000/rs6000-logue.cc b/gcc/config/rs6000/rs6000-logue.cc
> index 98846f781ec..9e08d9bb4d2 100644
> --- a/gcc/config/rs6000/rs6000-logue.cc
> +++ b/gcc/config/rs6000/rs6000-logue.cc
> @@ -1106,7 +1106,7 @@ rs6000_decl_ok_for_sibcall (tree decl)
>  	 r2 for its caller's TOC.  Such a function may make sibcalls to any
>  	 function, whether local or external, without restriction based on
>  	 TOC-save/restore rules.  */
> -      if (rs6000_pcrel_p ())
> +      if (TARGET_PCREL)
>  	return true;
>  
>        /* Otherwise, under the AIX or ELFv2 ABIs we can't allow sibcalls
> @@ -2583,7 +2583,7 @@ rs6000_global_entry_point_prologue_needed_p (void)
>      return false;
>  
>    /* PC-relative functions never generate a global entry point prologue.  */
> -  if (rs6000_pcrel_p ())
> +  if (TARGET_PCREL)
>      return false;
>  
>    /* Ensure we have a global entry point for thunks.   ??? We could
> @@ -4045,7 +4045,7 @@ rs6000_output_function_prologue (FILE *file)
>  					       patch_area_entry == 0);
>      }
>  
> -  else if (rs6000_pcrel_p ())
> +  else if (TARGET_PCREL)
>      {
>        const char *name = XSTR (XEXP (DECL_RTL (current_function_decl), 0), 0);
>        /* All functions compiled to use PC-relative addressing will
> diff --git a/gcc/config/rs6000/rs6000-protos.h b/gcc/config/rs6000/rs6000-protos.h
> index f70118ea40f..8ffec295d09 100644
> --- a/gcc/config/rs6000/rs6000-protos.h
> +++ b/gcc/config/rs6000/rs6000-protos.h
> @@ -158,7 +158,6 @@ extern rtx rs6000_allocate_stack_temp (machine_mode, bool, bool);
>  extern align_flags rs6000_loop_align (rtx);
>  extern void rs6000_split_logical (rtx [], enum rtx_code, bool, bool, bool);
>  extern bool rs6000_function_pcrel_p (struct function *);
> -extern bool rs6000_pcrel_p (void);
>  extern bool rs6000_fndecl_pcrel_p (const_tree);
>  extern void rs6000_output_addr_vec_elt (FILE *, int);
>  
> diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
> index 5f56c3ed85b..0c208cc2c0a 100644
> --- a/gcc/config/rs6000/rs6000.cc
> +++ b/gcc/config/rs6000/rs6000.cc
> @@ -4378,19 +4378,22 @@ rs6000_option_override_internal (bool global_init_p)
>    /* If the ABI has support for PC-relative relocations, enable it by default.
>       This test depends on the sub-target tests above setting the code model to
>       medium for ELF v2 systems.  */
> -  if (PCREL_SUPPORTED_BY_OS
> -      && (rs6000_isa_flags_explicit & OPTION_MASK_PCREL) == 0)
> -    rs6000_isa_flags |= OPTION_MASK_PCREL;
> -
> -  /* -mpcrel requires -mcmodel=medium, but we can't check TARGET_CMODEL until
> -      after the subtarget override options are done.  */
> -  else if (TARGET_PCREL && TARGET_CMODEL != CMODEL_MEDIUM)
> +  if (PCREL_SUPPORTED_BY_OS)
>      {
> -      if ((rs6000_isa_flags_explicit & OPTION_MASK_PCREL) != 0)
> +      /* PCREL on ELFv2 currently requires -mcmodel=medium, but we can't check
> +	 TARGET_CMODEL until after the subtarget override options are done.  */
> +      if (TARGET_PCREL && TARGET_CMODEL != CMODEL_MEDIUM)
>  	error ("%qs requires %qs", "-mpcrel", "-mcmodel=medium");
>  
> -      rs6000_isa_flags &= ~OPTION_MASK_PCREL;
> +      if (!TARGET_PCREL
> +	  && (rs6000_isa_flags_explicit & OPTION_MASK_PCREL) == 0
> +	  && TARGET_POWER10
> +	  && TARGET_PREFIXED
> +	  && TARGET_CMODEL == CMODEL_MEDIUM)
> +	rs6000_isa_flags |= OPTION_MASK_PCREL;
>      }
> +  else if (TARGET_PCREL)
> +    error ("use of %qs is invalid for this target", "-mpcrel");
>  
>    /* Enable -mmma by default on power10 systems.  */
>    if (TARGET_POWER10 && (rs6000_isa_flags_explicit & OPTION_MASK_MMA) == 0)
> @@ -9645,7 +9648,7 @@ rs6000_legitimize_tls_address (rtx addr, enum tls_model model)
>  
>    dest = gen_reg_rtx (Pmode);
>    if (model == TLS_MODEL_LOCAL_EXEC
> -      && (rs6000_tls_size == 16 || rs6000_pcrel_p ()))
> +      && (rs6000_tls_size == 16 || TARGET_PCREL))
>      {
>        rtx tlsreg;
>  
> @@ -9692,7 +9695,7 @@ rs6000_legitimize_tls_address (rtx addr, enum tls_model model)
>  	 them in the .got section.  So use a pointer to the .got section,
>  	 not one to secondary TOC sections used by 64-bit -mminimal-toc,
>  	 or to secondary GOT sections used by 32-bit -fPIC.  */
> -      if (rs6000_pcrel_p ())
> +      if (TARGET_PCREL)
>  	got = const0_rtx;
>        else if (TARGET_64BIT)
>  	got = gen_rtx_REG (Pmode, 2);
> @@ -9757,7 +9760,7 @@ rs6000_legitimize_tls_address (rtx addr, enum tls_model model)
>  	  rtx uns = gen_rtx_UNSPEC (Pmode, vec, UNSPEC_TLS_GET_ADDR);
>  	  set_unique_reg_note (get_last_insn (), REG_EQUAL, uns);
>  
> -	  if (rs6000_tls_size == 16 || rs6000_pcrel_p ())
> +	  if (rs6000_tls_size == 16 || TARGET_PCREL)
>  	    {
>  	      if (TARGET_64BIT)
>  		insn = gen_tls_dtprel_64 (dest, tmp1, addr);
> @@ -9798,7 +9801,7 @@ rs6000_legitimize_tls_address (rtx addr, enum tls_model model)
>  	  else
>  	    insn = gen_tls_got_tprel_32 (tmp2, got, addr);
>  	  emit_insn (insn);
> -	  if (rs6000_pcrel_p ())
> +	  if (TARGET_PCREL)
>  	    {
>  	      if (TARGET_64BIT)
>  		insn = gen_tls_tls_pcrel_64 (dest, tmp2, addr);
> @@ -14866,7 +14869,7 @@ rs6000_call_template_1 (rtx *operands, unsigned int funop, bool sibcall)
>  	    ? "+32768" : ""));
>  
>    static char str[32];  /* 1 spare */
> -  if (rs6000_pcrel_p ())
> +  if (TARGET_PCREL)
>      sprintf (str, "b%s %s@notoc%s", sibcall ? "" : "l", z, arg);
>    else if (DEFAULT_ABI == ABI_AIX || DEFAULT_ABI == ABI_ELFv2)
>      sprintf (str, "b%s %s%s%s", sibcall ? "" : "l", z, arg,
> @@ -15006,7 +15009,7 @@ rs6000_indirect_call_template_1 (rtx *operands, unsigned int funop,
>  		     rel64);
>  	}
>  
> -      const char *notoc = rs6000_pcrel_p () ? "_NOTOC" : "";
> +      const char *notoc = TARGET_PCREL ? "_NOTOC" : "";
>        const char *addend = (DEFAULT_ABI == ABI_V4 && TARGET_SECURE_PLT
>  			    && flag_pic == 2 ? "+32768" : "");
>        if (!speculate)
> @@ -15023,7 +15026,7 @@ rs6000_indirect_call_template_1 (rtx *operands, unsigned int funop,
>    else if (!speculate)
>      s += sprintf (s, "crset 2\n\t");
>  
> -  if (rs6000_pcrel_p ())
> +  if (TARGET_PCREL)
>      {
>        if (speculate)
>  	sprintf (s, "b%%T%ul", funop);
> @@ -20685,7 +20688,7 @@ rs6000_longcall_ref (rtx call_ref, rtx arg)
>      {
>        rtx base = const0_rtx;
>        int regno = 12;
> -      if (rs6000_pcrel_p ())
> +      if (TARGET_PCREL)
>  	{
>  	  rtx reg = gen_rtx_REG (Pmode, regno);
>  	  rtx u = gen_rtx_UNSPEC_VOLATILE (Pmode,
> @@ -25934,7 +25937,7 @@ rs6000_call_aix (rtx value, rtx func_desc, rtx tlsarg, rtx cookie)
>    if (!SYMBOL_REF_P (func)
>        || (DEFAULT_ABI == ABI_AIX && !SYMBOL_REF_FUNCTION_P (func)))
>      {
> -      if (!rs6000_pcrel_p ())
> +      if (!TARGET_PCREL)
>  	{
>  	  /* Save the TOC into its reserved slot before the call,
>  	     and prepare to restore it after the call.  */
> @@ -26040,7 +26043,7 @@ rs6000_call_aix (rtx value, rtx func_desc, rtx tlsarg, rtx cookie)
>    else
>      {
>        /* No TOC register needed for calls from PC-relative callers.  */
> -      if (!rs6000_pcrel_p ())
> +      if (!TARGET_PCREL)
>  	/* Direct calls use the TOC: for local calls, the callee will
>  	   assume the TOC register is set; for non-local calls, the
>  	   PLT stub needs the TOC register.  */
> @@ -26089,7 +26092,7 @@ rs6000_sibcall_aix (rtx value, rtx func_desc, rtx tlsarg, rtx cookie)
>      {
>        /* PCREL can do a sibling call to a longcall function
>  	 because we don't need to restore the TOC register.  */
> -      gcc_assert (rs6000_pcrel_p ());
> +      gcc_assert (TARGET_PCREL);
>        func_desc = rs6000_longcall_ref (func_desc, tlsarg);
>      }
>    else
> @@ -26116,7 +26119,7 @@ rs6000_sibcall_aix (rtx value, rtx func_desc, rtx tlsarg, rtx cookie)
>    insn = emit_call_insn (insn);
>  
>    /* Note use of the TOC register.  */
> -  if (!rs6000_pcrel_p ())
> +  if (!TARGET_PCREL)
>      use_reg (&CALL_INSN_FUNCTION_USAGE (insn),
>  	     gen_rtx_REG (Pmode, TOC_REGNUM));
>  
> @@ -26416,16 +26419,6 @@ rs6000_function_pcrel_p (struct function *fn)
>    return rs6000_fndecl_pcrel_p (fn->decl);
>  }
>  
> -/* Return whether we should generate PC-relative code for the current
> -   function.  */
> -bool
> -rs6000_pcrel_p ()
> -{
> -  return (DEFAULT_ABI == ABI_ELFv2
> -	  && (rs6000_isa_flags & OPTION_MASK_PCREL) != 0
> -	  && TARGET_CMODEL == CMODEL_MEDIUM);
> -}
> -
>  
>  /* Given an address (ADDR), a mode (MODE), and what the format of the
>     non-prefixed address (NON_PREFIXED_FORMAT) is, return the instruction format
> diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
> index 2a1b5ecfaee..97de6940e07 100644
> --- a/gcc/config/rs6000/rs6000.md
> +++ b/gcc/config/rs6000/rs6000.md
> @@ -11333,7 +11333,7 @@
>  			    (match_operand:P 3 "" "")]
>  			   UNSPECV_PLT_PCREL))]
>    "HAVE_AS_PLTSEQ && TARGET_ELF
> -   && rs6000_pcrel_p ()"
> +   && TARGET_PCREL"
>  {
>    return rs6000_pltseq_template (operands, RS6000_PLTSEQ_PLT_PCREL34);
>  }
> @@ -11418,7 +11418,7 @@
>    else if (INTVAL (operands[2]) & CALL_V4_CLEAR_FP_ARGS)
>      output_asm_insn ("creqv 6,6,6", operands);
>  
> -  if (rs6000_pcrel_p ())
> +  if (TARGET_PCREL)
>      return "bl %z0@notoc";
>    return (DEFAULT_ABI == ABI_V4 && flag_pic) ? "bl %z0@local" : "bl %z0";
>  }
> @@ -11439,7 +11439,7 @@
>    else if (INTVAL (operands[3]) & CALL_V4_CLEAR_FP_ARGS)
>      output_asm_insn ("creqv 6,6,6", operands);
>  
> -  if (rs6000_pcrel_p ())
> +  if (TARGET_PCREL)
>      return "bl %z1@notoc";
>    return (DEFAULT_ABI == ABI_V4 && flag_pic) ? "bl %z1@local" : "bl %z1";
>  }
> @@ -11614,7 +11614,7 @@
>  }
>    [(set_attr "type" "branch")
>     (set (attr "length")
> -	(if_then_else (match_test "rs6000_pcrel_p ()")
> +	(if_then_else (match_test "TARGET_PCREL")
>  	  (const_int 4)
>  	  (const_int 8)))])
>  
> @@ -11631,7 +11631,7 @@
>  }
>    [(set_attr "type" "branch")
>     (set (attr "length")
> -	(if_then_else (match_test "rs6000_pcrel_p ()")
> +	(if_then_else (match_test "TARGET_PCREL")
>  	    (const_int 4)
>  	    (const_int 8)))])
>  
> @@ -11705,7 +11705,7 @@
>  	 (match_operand 1))
>     (use (match_operand:SI 2 "immediate_operand" "n,n,n"))
>     (clobber (reg:P LR_REGNO))]
> -  "rs6000_pcrel_p ()"
> +  "TARGET_PCREL"
>  {
>    return rs6000_indirect_call_template (operands, 0);
>  }
> @@ -11742,7 +11742,7 @@
>  	      (match_operand:P 2 "unspec_tls" "")))
>     (use (match_operand:SI 3 "immediate_operand" "n,n,n"))
>     (clobber (reg:P LR_REGNO))]
> -  "rs6000_pcrel_p ()"
> +  "TARGET_PCREL"
>  {
>    return rs6000_indirect_call_template (operands, 1);
>  }
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr111045.c b/gcc/testsuite/gcc.target/powerpc/pr111045.c
> new file mode 100644
> index 00000000000..6fd2773eb35
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr111045.c
> @@ -0,0 +1,15 @@
> +/* PR target/111045 */
> +/* { dg-require-effective-target power10_ok } */
> +/* { dg-options "-O2 -mdejagnu-cpu=power10" } */
> +
> +/* Verify we do not generate a PCREL access on ABIs that doesn't support it.  */
> +
> +static unsigned short s;
> +
> +unsigned short *
> +foo (void)
> +{
> +  return &s;
> +}
> +
> +/* { dg-final { scan-assembler-not {\m@pcrel\M} { target { ! powerpc_pcrel } } } } */
> diff --git a/gcc/testsuite/gcc.target/powerpc/float128-constant.c b/gcc/testsuite/gcc.target/powerpc/float128-constant.c
> index e3286a786a5..4728f4891da 100644
> --- a/gcc/testsuite/gcc.target/powerpc/float128-constant.c
> +++ b/gcc/testsuite/gcc.target/powerpc/float128-constant.c
> @@ -155,6 +155,7 @@ return_longlong_neg_0 (void)
>  }
>  
>  /* { dg-final { scan-assembler-times {\mlxvkq\M}    19 } } */
> -/* { dg-final { scan-assembler-times {\mplxv\M}      3 } } */
> +/* { dg-final { scan-assembler-times {\mplxv\M}      3 { target { powerpc_pcrel } } } } */
> +/* { dg-final { scan-assembler-times {\mlxv\M}       3 { target { ! powerpc_pcrel } } } } */
>  /* { dg-final { scan-assembler-times {\mxxspltib\M}  1 } } */
>