[gcc(refs/users/meissner/heads/work252-bugs)] PR target/120681 - allow -mcmodel=large with PC relative addressing

https://gcc.gnu.org/g:16c19adea8fbf54ff013c7e1996df7e299f9cd20

commit 16c19adea8fbf54ff013c7e1996df7e299f9cd20
Author: Michael Meissner <[email protected]>
Date:   Fri Jul 24 00:28:31 2026 -0400

    PR target/120681 - allow -mcmodel=large with PC relative addressing
    
    When I implemented the pc-relative support for power10 in GCC, I
    disabled using pc-relative support for -mcmodel=large.  At the time, I
    didn't want to dig into the issues.  It is now time to allow
    -mcmodel=large to generate pc-relative code.
    
    This patch allows -mcmodel=large to use prefixed addressing on power10,
    power11, and possibly other future PowerPC processors in addition to
    the current -mcmodel=medium support.
    
    I have committed all of the patches in my backlog (dense math registers, other
    -mcpu=future instructions, random bug fixes, support for _Float16 and
    __bfloat16, and optimizations for vector logical operations on power10/power11)
    into the IBM vendor branch:
    
            vendors/ibm/gcc-17-future
    
    2026-07-24  Michael Meissner  <[email protected]>
    
    gcc/
    
            PR target/120681
            * config/rs6000/linux64.h (PCREL_SUPPORTED_BY_OS): Allow large
            code model as well as medium code model.
            * config/rs6000/rs6000.cc (rs6000_option_override_internal):
            Likewise.
            (rs6000_elf_declare_function_name): Don't create the
            local/non-local labels for large code model if we are using
            PC-relative addressing.
    
    gcc/testsuite/
    
            PR target/120681
            * gcc.target/powerpc/pr120681.c: New test.

Diff:
---
 gcc/config/rs6000/linux64.h                 |  5 +++--
 gcc/config/rs6000/rs6000.cc                 | 13 ++++++-----
 gcc/testsuite/gcc.target/powerpc/pr120681.c | 34 +++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 7 deletions(-)

diff --git a/gcc/config/rs6000/linux64.h b/gcc/config/rs6000/linux64.h
index 1af710303687..c892930a8a93 100644
--- a/gcc/config/rs6000/linux64.h
+++ b/gcc/config/rs6000/linux64.h
@@ -564,7 +564,8 @@ extern int dot_symbols;
 
 /* 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.  */
+   the medium/large code models.  */
 #define PCREL_SUPPORTED_BY_OS	(TARGET_POWER10 && TARGET_PREFIXED	\
 				 && ELFv2_ABI_CHECK			\
-				 && TARGET_CMODEL == CMODEL_MEDIUM)
+				 && (TARGET_CMODEL == CMODEL_MEDIUM	\
+				     || TARGET_CMODEL == CMODEL_LARGE))
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index c620d1a31e87..757a807b726f 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -4426,12 +4426,15 @@ rs6000_option_override_internal (bool global_init_p)
       && (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)
+  /* -mpcrel requires medium or large code models, but we can't check
+      TARGET_CMODEL until after the subtarget override options are done.  */
+  else if (TARGET_PCREL
+	   && TARGET_CMODEL != CMODEL_MEDIUM
+	   && TARGET_CMODEL != CMODEL_LARGE)
     {
       if ((rs6000_isa_flags_explicit & OPTION_MASK_PCREL) != 0)
-	error ("%qs requires %qs", "-mpcrel", "-mcmodel=medium");
+	error ("%qs requires %qs or %qs", "-mpcrel", "-mcmodel=medium",
+	       "-mcmodel=large");
 
       rs6000_isa_flags &= ~OPTION_MASK_PCREL;
     }
@@ -21528,7 +21531,7 @@ rs6000_elf_declare_function_name (FILE *file, const char *name, tree decl)
   ASM_OUTPUT_TYPE_DIRECTIVE (file, name, "function");
   ASM_DECLARE_RESULT (file, DECL_RESULT (decl));
 
-  if (TARGET_CMODEL == CMODEL_LARGE
+  if (TARGET_CMODEL == CMODEL_LARGE && !TARGET_PCREL
       && rs6000_global_entry_point_prologue_needed_p ())
     {
       char buf[256];
diff --git a/gcc/testsuite/gcc.target/powerpc/pr120681.c b/gcc/testsuite/gcc.target/powerpc/pr120681.c
new file mode 100644
index 000000000000..d883d1c8a951
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr120681.c
@@ -0,0 +1,34 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target powerpc_elfv2 } */
+/* { dg-require-effective-target powerpc_pcrel } */
+/* { dg-options "-mdejagnu-cpu=power10 -O2 -mcmodel=large" } */
+
+/* PR target/120681 -- verify that -mcpu=power10 -mcmodel=large uses PC
+   relative addressing instead of using TOC addressing.  */
+
+#ifndef TYPE
+#define TYPE unsigned long
+#endif
+
+extern TYPE global_var;
+
+void
+set_global (TYPE value)
+{
+  /*
+   * Generate:
+   * pld 9,global_var@got@pcrel
+   * std 3,0(9)
+   *
+   * Not:
+   * addis 9,2,.LC0@toc@ha
+   * ld    9,.LC0@toc@l(9)
+   * std   3,0(9)
+   */
+
+  global_var = value;
+}
+
+/* { dg-final { scan-assembler     {@got@pcrel} } } */
+/* { dg-final { scan-assembler-not {@toc@ha}    } } */
+/* { dg-final { scan-assembler-not {@toc@l}     } } */