[gcc/devel/omp/gcc-9] backport for PR91289

[Tobias Burnus]

https://gcc.gnu.org/g:738aa869a1bc7628b8bd882dedc6967052c4d234

commit 738aa869a1bc7628b8bd882dedc6967052c4d234
Author: Segher Boessenkool <segher@kernel.crashing.org>
Date:   Tue Nov 5 18:17:03 2019 +0100

    backport for PR91289
    
    	Backport from trunk
    	2019-10-26  Segher Boessenkool  <segher@kernel.crashing.org>
    
    	PR target/91289
    	* config/rs6000/rs6000.c (rs6000_emit_allocate_stack): Don't add an
    	immediate to r0; use r11 instead.  Save and restore r11 to r0 around
    	this.
    
    From-SVN: r277855

Diff:
---
 gcc/ChangeLog              | 10 ++++++++++
 gcc/config/rs6000/rs6000.c | 12 ++++++++----
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index d844408..47d9b3e 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,13 @@
+2019-11-05  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	Backport from trunk
+	2019-10-26  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR target/91289
+	* config/rs6000/rs6000.c (rs6000_emit_allocate_stack): Don't add an
+	immediate to r0; use r11 instead.  Save and restore r11 to r0 around
+	this.
+
 2019-11-05  Andreas Krebbel  <krebbel@linux.ibm.com>
 
 	Backport from mainline
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 2a8932d..a670096 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -25833,10 +25833,14 @@ rs6000_emit_allocate_stack (HOST_WIDE_INT size, rtx copy_reg, int copy_off)
 						    stack_limit_rtx,
 						    GEN_INT (size)));
 
-	  emit_insn (gen_elf_high (tmp_reg, toload));
-	  emit_insn (gen_elf_low (tmp_reg, tmp_reg, toload));
-	  emit_insn (gen_cond_trap (LTU, stack_reg, tmp_reg,
-				    const0_rtx));
+	  /* We cannot use r0 with elf_low.  Lamely solve this problem by
+	     moving registers around.  */
+	  rtx r11_reg = gen_rtx_REG (Pmode, 11);
+	  emit_move_insn (tmp_reg, r11_reg);
+	  emit_insn (gen_elf_high (r11_reg, toload));
+	  emit_insn (gen_elf_low (r11_reg, r11_reg, toload));
+	  emit_insn (gen_cond_trap (LTU, stack_reg, r11_reg, const0_rtx));
+	  emit_move_insn (r11_reg, tmp_reg);
 	}
       else
 	warning (0, "stack limit expression is not supported");