From: Alan Modra <amodra@gmail.com>
Date: Fri, 18 Sep 2020 13:33:11 +0000 (+0930)
Subject: [RS6000] PR97107, libgo fails to build for power10
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=199baa71f7a6c8f255afdda03cd3b2644f8f0fcd;p=gcc.git

[RS6000] PR97107, libgo fails to build for power10

Calls from split-stack code to non-split-stack code need to expand
mapped stack memory via __morestack.  Even tail calls.

__morestack is quite a surprising function on powerpc in that it calls
back to its caller, and a tail call will continue running in the
context of extra mapped stack.

	PR target/97107
	* config/rs6000/rs6000-internal.h (struct rs6000_stack): Improve
	calls_p comment.
	* config/rs6000/rs6000-logue.c (rs6000_stack_info): Likewise.
	(rs6000_expand_split_stack_prologue): Emit the prologue for
	functions that make a sibling call.
---

diff --git a/gcc/config/rs6000/rs6000-internal.h b/gcc/config/rs6000/rs6000-internal.h
index 9caef013a71..32681b6cece 100644
--- a/gcc/config/rs6000/rs6000-internal.h
+++ b/gcc/config/rs6000/rs6000-internal.h
@@ -32,7 +32,7 @@ typedef struct rs6000_stack {
   int cr_save_p;		/* true if the CR reg needs to be saved */
   unsigned int vrsave_mask;	/* mask of vec registers to save */
   int push_p;			/* true if we need to allocate stack space */
-  int calls_p;			/* true if the function makes any calls */
+  int calls_p;			/* true if there are non-sibling calls */
   int world_save_p;		/* true if we're saving *everything*:
 				   r13-r31, cr, f14-f31, vrsave, v20-v31  */
   enum rs6000_abi abi;		/* which ABI to use */
diff --git a/gcc/config/rs6000/rs6000-logue.c b/gcc/config/rs6000/rs6000-logue.c
index 0f88ec19929..d90cd5736e1 100644
--- a/gcc/config/rs6000/rs6000-logue.c
+++ b/gcc/config/rs6000/rs6000-logue.c
@@ -714,7 +714,7 @@ rs6000_stack_info (void)
   info->altivec_size = 16 * (LAST_ALTIVEC_REGNO + 1
 				 - info->first_altivec_reg_save);
 
-  /* Does this function call anything?  */
+  /* Does this function call anything (apart from sibling calls)?  */
   info->calls_p = (!crtl->is_leaf || cfun->machine->ra_needs_full_frame);
 
   /* Determine if we need to save the condition code registers.  */
@@ -5479,7 +5479,18 @@ rs6000_expand_split_stack_prologue (void)
   gcc_assert (flag_split_stack && reload_completed);
 
   if (!info->push_p)
-    return;
+    {
+      /* We need the -fsplit-stack prologue for functions that make
+	 tail calls.  Tail calls don't count against crtl->is_leaf.
+	 Note that we are called inside a sequence.  get_insns will
+	 just return that (as yet empty) sequence, so instead we
+	 access the function rtl with get_topmost_sequence.  */
+      for (insn = get_topmost_sequence ()->first; insn; insn = NEXT_INSN (insn))
+	if (CALL_P (insn))
+	  break;
+      if (!insn)
+	return;
+    }
 
   if (global_regs[29])
     {