This patch is the first of two changes to genmatch that don't affect
the executable code, but reduce the amount of debugging information
generated in stage3 of a build, but adhering more closely to GNU style
guidelines.
This patch avoids generating a switch with a single case statement,
instead preferring to use an "if (TREE_CODE (...) == SSA_NAME)" idiom.
These should compile to the same instructions, but the switch requires
more lines, especially when a debugger may set a break point on the
switch, the case, or the (obligatory) final "default:;". This reduces
the size of gimple-match.o by 53K on x86_64-pc-linux-gnu.
This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
and make -k check with no new failures. Ok for mainline?
2022-03-16 Roger Sayle <ro...@nextmovesoftware.com>
gcc/ChangeLog
* gcc/genmatch.cc (dt_node::gen_kids_1): Introduce use_switch
logic that prefers to generate an if statement rather than a
switch containing a single case (and a default).
Thanks in advance,
Roger
--
diff --git a/gcc/genmatch.cc b/gcc/genmatch.cc
index 2eda730..c4e22ef 100644
--- a/gcc/genmatch.cc
+++ b/gcc/genmatch.cc
@@ -2999,6 +2999,7 @@ dt_node::gen_kids_1 (FILE *f, int indent, bool gimple,
int depth,
unsigned gexprs_len = generic_exprs.length ();
unsigned fns_len = fns.length ();
unsigned gfns_len = generic_fns.length ();
+ bool use_switch = true;
if (exprs_len || fns_len || gexprs_len || gfns_len)
{
@@ -3011,7 +3012,30 @@ dt_node::gen_kids_1 (FILE *f, int indent, bool gimple,
int depth,
else
generic_exprs[0]->get_name (kid_opname);
- fprintf_indent (f, indent, "switch (TREE_CODE (%s))\n", kid_opname);
+ if (gexprs_len == 0 && gfns_len == 0)
+ {
+ fprintf_indent (f, indent, "if (TREE_CODE (%s) == SSA_NAME)\n",
+ kid_opname);
+ use_switch = false;
+ }
+ else if (exprs_len == 0
+ && fns_len == 0
+ && gexprs_len == 1
+ && gfns_len == 0)
+ {
+ expr *e = as_a <expr *>(generic_exprs[0]->op);
+ id_base *op = e->operation;
+ /* id_base doesn't have a != operator. */
+ if (!(*op == CONVERT_EXPR || *op == NOP_EXPR))
+ {
+ fprintf_indent (f, indent, "if (TREE_CODE (%s) == %s)\n",
+ kid_opname, op->id);
+ use_switch = false;
+ }
+ }
+
+ if (use_switch)
+ fprintf_indent (f, indent, "switch (TREE_CODE (%s))\n", kid_opname);
fprintf_indent (f, indent, " {\n");
indent += 2;
}
@@ -3019,8 +3043,8 @@ dt_node::gen_kids_1 (FILE *f, int indent, bool gimple,
int depth,
if (exprs_len || fns_len)
{
depth++;
- fprintf_indent (f, indent,
- "case SSA_NAME:\n");
+ if (use_switch)
+ fprintf_indent (f, indent, "case SSA_NAME:\n");
fprintf_indent (f, indent,
" if (gimple *_d%d = get_def (valueize, %s))\n",
depth, kid_opname);
@@ -3103,7 +3127,8 @@ dt_node::gen_kids_1 (FILE *f, int indent, bool gimple,
int depth,
}
}
- fprintf_indent (f, indent, " break;\n");
+ if (use_switch)
+ fprintf_indent (f, indent, " break;\n");
}
for (unsigned i = 0; i < generic_exprs.length (); ++i)
@@ -3115,12 +3140,18 @@ dt_node::gen_kids_1 (FILE *f, int indent, bool gimple,
int depth,
else if (*op == SSA_NAME && (exprs_len || fns_len))
/* Already handled above. */
continue;
- else
+ else if (use_switch)
fprintf_indent (f, indent, "case %s:\n", op->id);
- fprintf_indent (f, indent, " {\n");
- generic_exprs[i]->gen (f, indent + 4, gimple, depth);
- fprintf_indent (f, indent, " break;\n");
- fprintf_indent (f, indent, " }\n");
+
+ if (use_switch)
+ {
+ fprintf_indent (f, indent, " {\n");
+ generic_exprs[i]->gen (f, indent + 4, gimple, depth);
+ fprintf_indent (f, indent, " break;\n");
+ fprintf_indent (f, indent, " }\n");
+ }
+ else
+ generic_exprs[i]->gen (f, indent + 2, gimple, depth);
}
if (gfns_len)
@@ -3157,7 +3188,8 @@ dt_node::gen_kids_1 (FILE *f, int indent, bool gimple,
int depth,
if (exprs_len || fns_len || gexprs_len || gfns_len)
{
indent -= 4;
- fprintf_indent (f, indent, " default:;\n");
+ if (use_switch)
+ fprintf_indent (f, indent, " default:;\n");
fprintf_indent (f, indent, " }\n");
}
