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.cc (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 --git a/gcc/config/sparc/sparc.cc b/gcc/config/sparc/sparc.cc
index aca925befe15a65959dee05d4a2012386250cb0c..a47537365a8c4c9f54a4cee158a51dae6ef483f0 100644 (file)
--- a/gcc/config/sparc/sparc.cc
+++ b/gcc/config/sparc/sparc.cc
@@ -6050,6 +6050,9 @@ 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
     {
@@ -6064,13 +6067,7 @@ 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
@@ -6166,8 +6163,8 @@ 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)
        {
@@ -6254,6 +6251,9 @@ 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)
@@ -6304,15 +6304,15 @@ 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)));