i386.c (ix86_output_main_function_alignment_hack): New function.

	* i386.c (ix86_output_main_function_alignment_hack): New function.
	(TARGET_ASM_FUNCTION_PROLOGUE): Default to it.

	* flow.c (mark_dfs_back_edges): Move from loop_p ; mark back
	edges by EDGE_DFS_BACK flag.
	(dump_edge_info): Add dfs_back flag.
	* basic-block.h (EDGE_DFS_BACK): New constant.
	(mark_dfs_back_edges): Declare.
	* alias.c (loop_p): Remove.
	(mark_constant_function): Use mark_dfs_back_edges.

	* reg-stack.c (block_info_def): Add predecesors counter and stack_out.
	(reg_to_stack): Call mark_dfs_back_edges; count the predecesors.
	(compensate_edge): Break out from ...
	(convert_regs_1): ... here; do smart choosing of stack_out to copy.
	(convert_regs_2): Set block_done once block is really done;
	Do updating of the predecesors counts.

	* toplev.c (rest_of_compilation): Recompute block_for_insn
	before post-reload cfg_cleanup.
	* function.c (thread_prologue_epilogue_insns):
	Call set_block_for_new_insns when emitting prologue directly.

From-SVN: r44486

1 files changed, 47 insertions, 0 deletions

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 725a984..9017207 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -574,6 +574,7 @@ static HOST_WIDE_INT ix86_GOT_alias_set PARAMS ((void));
 static void ix86_adjust_counter PARAMS ((rtx, HOST_WIDE_INT));
 static rtx ix86_expand_aligntest PARAMS ((rtx, int));
 static void ix86_expand_strlensi_unroll_1 PARAMS ((rtx, rtx));
+static void ix86_output_main_function_alignment_hack PARAMS ((FILE *f, int));
 
 struct ix86_address
 {
@@ -634,6 +635,10 @@ static int ix86_comp_type_attributes PARAMS ((tree, tree));
 							  HOST_WIDE_INT));
 #  undef TARGET_ASM_FUNCTION_PROLOGUE
 #  define TARGET_ASM_FUNCTION_PROLOGUE ix86_osf_output_function_prologue
+#else
+#  undef TARGET_ASM_FUNCTION_PROLOGUE
+#  define TARGET_ASM_FUNCTION_PROLOGUE \
+   ix86_output_main_function_alignment_hack
 #endif
 
 #undef TARGET_ASM_OPEN_PAREN
@@ -10775,3 +10780,45 @@ ix86_memory_move_cost (mode, class, in)
 		* (int) GET_MODE_SIZE (mode) / 4);
     }
 }
+
+/* Most of current runtimes (Jul 2001) do not align stack properly when
+   entering main, so emit an wrapper to align stack before the real main
+   code is called.
+  
+   This can eventually go if we manage to fix the runtimes or teach gcc
+   to dynamically align stack in main automatically.
+
+   Adding check to configure is probably not good idea, as binarry can move
+   from one shared library to older.  */
+
+static void
+ix86_output_main_function_alignment_hack (file, size)
+     FILE *file;
+     int size ATTRIBUTE_UNUSED;
+{
+  rtx label;
+  char buf[256];
+  /* Check that we see main function with maximally 8 bytes of arguments.
+     if so, emit the hack to align stack for runtimes, where this constraint
+     is broken.  */
+  if (strcmp (cfun->name, "main"))
+    return;
+  if (cfun->pops_args || cfun->args_size > 12)
+    return;
+  if (PREFERRED_STACK_BOUNDARY <= 2)
+    return;
+  label = gen_label_rtx ();
+  fprintf (file, "\tpushl\t%%ebp\n");
+  fprintf (file, "\tmovl\t%%esp, %%ebp\n");
+  fprintf (file, "\tandl\t$0xfffffff0, %%esp\n");
+  fprintf (file, "\tpushl\t%%ebp\n");
+  fprintf (file, "\tpushl\t16(%%ebp)\n");
+  fprintf (file, "\tpushl\t12(%%ebp)\n");
+  fprintf (file, "\tpushl\t8(%%ebp)\n");
+  fprintf (file, "\tcall\t");
+  ASM_GENERATE_INTERNAL_LABEL (buf, "L", CODE_LABEL_NUMBER (label));
+  assemble_name (file, buf);
+  fprintf (file, "\n\tleave\n");
+  fprintf (file, "\tret\n");
+  ASM_OUTPUT_INTERNAL_LABEL (file, "L", CODE_LABEL_NUMBER (label));
+}