[v2] rs6000: Entry point generation for functions using PC-relative addressing

Message ID f9338de3-29b4-7239-648c-c12d3ee00353@linux.ibm.com
State New
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  • [v2] rs6000: Entry point generation for functions using PC-relative addressing
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Commit Message

Bill Schmidt May 23, 2019, 3:21 p.m.
Hi,

Functions using PC-relative addressing do not use a TOC, so there is no need for
a global entry point for TOC setup.  Ensure we never generate a global entry
point, and use a .localentry directive that sets the upper st_other bits to 1.
Also change a function name for clarity, and move a var decl off of paths
where it will not be executed, per previous comments by Segher.

Bootstrapped and tested on powerpc64le-unknown-linux-gnu with no regressions.
Is this okay for trunk?

Thanks!

Bill


[gcc]

2019-05-23  Bill Schmidt  <wschmidt@linux.ibm.com>

	* config/rs6000/rs6000.c (rs6000_global_entry_point_needed_p):
	Rename to rs6000_global_entry_point_prologue_needed_p.  Return
	false for PC-relative functions.
	(rs6000_output_function_prologue): Change called function name to
	rs6000_global_entry_point_prologue_needed_p.  Emit ".localentry
	name,1" for PC-relative functions.
	(rs6000_elf_declare_function_name): Change called function name to
	rs6000_global_entry_point_prologue_needed_p.

[gcc/testsuite]

2019-05-23  Bill Schmidt  <wschmidt@linux.ibm.com>

	* gcc.target/powerpc/localentry-1.c: New file.

Comments

Segher Boessenkool May 23, 2019, 4:34 p.m. | #1
On Thu, May 23, 2019 at 10:21:44AM -0500, Bill Schmidt wrote:
> Functions using PC-relative addressing do not use a TOC, so there is no need for

> a global entry point for TOC setup.  Ensure we never generate a global entry

> point, and use a .localentry directive that sets the upper st_other bits to 1.

> Also change a function name for clarity, and move a var decl off of paths

> where it will not be executed, per previous comments by Segher.

> 

> Bootstrapped and tested on powerpc64le-unknown-linux-gnu with no regressions.

> Is this okay for trunk?


Yes please.  Thanks,


Segher


> 2019-05-23  Bill Schmidt  <wschmidt@linux.ibm.com>

> 

> 	* config/rs6000/rs6000.c (rs6000_global_entry_point_needed_p):

> 	Rename to rs6000_global_entry_point_prologue_needed_p.  Return

> 	false for PC-relative functions.

> 	(rs6000_output_function_prologue): Change called function name to

> 	rs6000_global_entry_point_prologue_needed_p.  Emit ".localentry

> 	name,1" for PC-relative functions.

> 	(rs6000_elf_declare_function_name): Change called function name to

> 	rs6000_global_entry_point_prologue_needed_p.

> 

> [gcc/testsuite]

> 

> 2019-05-23  Bill Schmidt  <wschmidt@linux.ibm.com>

> 

> 	* gcc.target/powerpc/localentry-1.c: New file.

Patch

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 7a2e43fd72a..3d5cf9e4ece 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -26180,7 +26180,7 @@  split_stack_arg_pointer_used_p (void)
 /* Return whether we need to emit an ELFv2 global entry point prologue.  */
 
 static bool
-rs6000_global_entry_point_needed_p (void)
+rs6000_global_entry_point_prologue_needed_p (void)
 {
   /* Only needed for the ELFv2 ABI.  */
   if (DEFAULT_ABI != ABI_ELFv2)
@@ -26191,6 +26191,10 @@  rs6000_global_entry_point_needed_p (void)
   if (TARGET_SINGLE_PIC_BASE)
     return false;
 
+  /* PC-relative functions never generate a global entry point prologue.  */
+  if (rs6000_pcrel_p (cfun))
+    return false;
+
   /* Ensure we have a global entry point for thunks.   ??? We could
      avoid that if the target routine doesn't need a global entry point,
      but we do not know whether this is the case at this point.  */
@@ -27547,10 +27551,9 @@  rs6000_output_function_prologue (FILE *file)
 
   /* ELFv2 ABI r2 setup code and local entry point.  This must follow
      immediately after the global entry point label.  */
-  if (rs6000_global_entry_point_needed_p ())
+  if (rs6000_global_entry_point_prologue_needed_p ())
     {
       const char *name = XSTR (XEXP (DECL_RTL (current_function_decl), 0), 0);
-
       (*targetm.asm_out.internal_label) (file, "LCF", rs6000_pic_labelno);
 
       if (TARGET_CMODEL != CMODEL_LARGE)
@@ -27601,6 +27604,19 @@  rs6000_output_function_prologue (FILE *file)
       fputs ("\n", file);
     }
 
+  else if (rs6000_pcrel_p (cfun))
+    {
+      const char *name = XSTR (XEXP (DECL_RTL (current_function_decl), 0), 0);
+      /* All functions compiled to use PC-relative addressing will
+	 have a .localentry value of 0 or 1.  For now we set it to
+	 1 all the time, indicating that the function may clobber
+	 the TOC register r2.  Later we may optimize this by setting
+	 it to 0 if the function is a leaf and does not clobber r2.  */
+      fputs ("\t.localentry\t", file);
+      assemble_name (file, name);
+      fputs (",1\n", file);
+    }
+
   /* Output -mprofile-kernel code.  This needs to be done here instead of
      in output_function_profile since it must go after the ELFv2 ABI
      local entry point.  */
@@ -33335,7 +33351,8 @@  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 && rs6000_global_entry_point_needed_p ())
+  if (TARGET_CMODEL == CMODEL_LARGE
+      && rs6000_global_entry_point_prologue_needed_p ())
     {
       char buf[256];
 
diff --git a/gcc/testsuite/gcc.target/powerpc/localentry-1.c b/gcc/testsuite/gcc.target/powerpc/localentry-1.c
new file mode 100644
index 00000000000..ce687a7f6ec
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/localentry-1.c
@@ -0,0 +1,18 @@ 
+/* { dg-do compile } */
+/* { dg-options "-mdejagnu-cpu=future -O2" } */
+/* { dg-require-effective-target powerpc_elfv2 } */
+
+/* Ensure we generate ".localentry fn,1" for both leaf and non-leaf
+   functions.  */
+
+extern int y (int);
+
+int x (void)
+{
+  return y (5);
+}
+
+void z (void) { };
+
+/* { dg-final { scan-assembler {\.localentry\t\mx,1\M} } } */
+/* { dg-final { scan-assembler {\.localentry\t\mz,1\M} } } */