[gcc r11-10311] Fix PR target/107248

[Eric Botcazou <ebotcazou@gcc.gnu.org>]

https://gcc.gnu.org/g:3f4b65df625edae3e8829718af721ad2330b3f22

commit r11-10311-g3f4b65df625edae3e8829718af721ad2330b3f22
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Fri Oct 14 11:52:04 2022 +0200

    Fix PR target/107248
    
    This is the infamous PR rtl-optimization/38644 rearing its ugly head for
    leaf functions on SPARC more than a decade later...  Richard E.'s generic
    solution has never been implemented so let's do as other RISC back-ends did.
    
    gcc/
            PR target/107248
            * config/sparc/sparc.c (sparc_expand_prologue): Emit a frame
            blockage for leaf functions.
            (sparc_flat_expand_prologue): Emit frame instead of full blockage.
            (sparc_expand_epilogue): Emit a frame blockage for leaf functions.
            (sparc_flat_expand_epilogue): Emit frame instead of full blockage.

Diff:
---
 gcc/config/sparc/sparc.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/gcc/config/sparc/sparc.c b/gcc/config/sparc/sparc.c
index e4fe2f065c9..a9196d68863 100644
--- a/gcc/config/sparc/sparc.c
+++ b/gcc/config/sparc/sparc.c
@@ -6122,6 +6122,9 @@ sparc_expand_prologue (void)
 	}
 
       RTX_FRAME_RELATED_P (insn) = 1;
+
+      /* Ensure no memory access is done before the frame is established.  */
+      emit_insn (gen_frame_blockage ());
     }
   else
     {
@@ -6136,13 +6139,7 @@ sparc_expand_prologue (void)
 	  /* %sp is not the CFA register anymore.  */
 	  emit_insn (gen_stack_pointer_inc (GEN_INT (4096 - size)));
 
-	  /* Make sure no %fp-based store is issued until after the frame is
-	     established.  The offset between the frame pointer and the stack
-	     pointer is calculated relative to the value of the stack pointer
-	     at the end of the function prologue, and moving instructions that
-	     access the stack via the frame pointer between the instructions
-	     that decrement the stack pointer could result in accessing the
-	     register window save area, which is volatile.  */
+	  /* Likewise.  */
 	  emit_insn (gen_frame_blockage ());
 	}
       else
@@ -6238,8 +6235,8 @@ sparc_flat_expand_prologue (void)
 	}
       RTX_FRAME_RELATED_P (insn) = 1;
 
-      /* Ensure nothing is scheduled until after the frame is established.  */
-      emit_insn (gen_blockage ());
+      /* Ensure no memory access is done before the frame is established.  */
+      emit_insn (gen_frame_blockage ());
 
       if (frame_pointer_needed)
 	{
@@ -6326,6 +6323,9 @@ sparc_expand_epilogue (bool for_eh)
     ; /* do nothing.  */
   else if (sparc_leaf_function_p)
     {
+      /* Ensure no memory access is done after the frame is destroyed.  */
+      emit_insn (gen_frame_blockage ());
+
       if (size <= 4096)
 	emit_insn (gen_stack_pointer_inc (GEN_INT (size)));
       else if (size <= 8192)
@@ -6376,15 +6376,15 @@ sparc_flat_expand_epilogue (bool for_eh)
     ; /* do nothing.  */
   else if (frame_pointer_needed)
     {
-      /* Make sure the frame is destroyed after everything else is done.  */
-      emit_insn (gen_blockage ());
+      /* Ensure no memory access is done after the frame is destroyed.  */
+      emit_insn (gen_frame_blockage ());
 
       emit_move_insn (stack_pointer_rtx, gen_rtx_REG (Pmode, 1));
     }
   else
     {
       /* Likewise.  */
-      emit_insn (gen_blockage ());
+      emit_insn (gen_frame_blockage ());
 
       if (size <= 4096)
 	emit_insn (gen_stack_pointer_inc (GEN_INT (size)));