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* [PATCH] switch expansion: limit JT growth param values
@ 2023-01-11 10:30 Martin Liška
  2023-01-11 12:05 ` Richard Biener
  0 siblings, 1 reply; 2+ messages in thread
From: Martin Liška @ 2023-01-11 10:30 UTC (permalink / raw)
  To: gcc-patches

Currently, one can request a huge jump table creation which
leads to a non-sensual huge output. Moreover, use auto_vec rather
than a stack-allocated array.

Patch can bootstrap on x86_64-linux-gnu and survives regression tests.

Ready to be installed?
Thanks,
Martin

	PR middle-end/107976

gcc/ChangeLog:

	* params.opt: Limit JT params.
	* stmt.cc (emit_case_dispatch_table): Use auto_vec.
---
 gcc/params.opt | 4 ++--
 gcc/stmt.cc    | 9 ++++-----
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/gcc/params.opt b/gcc/params.opt
index e178dec1600..3454700eb91 100644
--- a/gcc/params.opt
+++ b/gcc/params.opt
@@ -327,11 +327,11 @@ Common Joined UInteger Var(param_iv_max_considered_uses) Init(250) Param Optimiz
 Bound on number of iv uses in loop optimized in iv optimizations.
 
 -param=jump-table-max-growth-ratio-for-size=
-Common Joined UInteger Var(param_jump_table_max_growth_ratio_for_size) Init(300) Param Optimization
+Common Joined UInteger Var(param_jump_table_max_growth_ratio_for_size) Init(300) IntegerRange(0, 10000) Param Optimization
 The maximum code size growth ratio when expanding into a jump table (in percent).  The parameter is used when optimizing for size.
 
 -param=jump-table-max-growth-ratio-for-speed=
-Common Joined UInteger Var(param_jump_table_max_growth_ratio_for_speed) Init(800) Param Optimization
+Common Joined UInteger Var(param_jump_table_max_growth_ratio_for_speed) Init(800) IntegerRange(0, 10000) Param Optimization
 The maximum code size growth ratio when expanding into a jump table (in percent).  The parameter is used when optimizing for speed.
 
 -param=l1-cache-line-size=
diff --git a/gcc/stmt.cc b/gcc/stmt.cc
index 82a3e1035ec..b239c02018a 100644
--- a/gcc/stmt.cc
+++ b/gcc/stmt.cc
@@ -746,7 +746,7 @@ emit_case_dispatch_table (tree index_expr, tree index_type,
 			  tree range, basic_block stmt_bb)
 {
   int i, ncases;
-  rtx *labelvec;
+  auto_vec<rtx> labelvec;
   rtx_insn *fallback_label = label_rtx (case_list[0].m_code_label);
   rtx_code_label *table_label = gen_label_rtx ();
   bool has_gaps = false;
@@ -779,8 +779,7 @@ emit_case_dispatch_table (tree index_expr, tree index_type,
   /* Get table of labels to jump to, in order of case index.  */
 
   ncases = tree_to_shwi (range) + 1;
-  labelvec = XALLOCAVEC (rtx, ncases);
-  memset (labelvec, 0, ncases * sizeof (rtx));
+  labelvec.safe_grow_cleared (ncases);
 
   for (unsigned j = 0; j < case_list.length (); j++)
     {
@@ -860,11 +859,11 @@ emit_case_dispatch_table (tree index_expr, tree index_type,
     emit_jump_table_data (gen_rtx_ADDR_DIFF_VEC (CASE_VECTOR_MODE,
 						 gen_rtx_LABEL_REF (Pmode,
 								    table_label),
-						 gen_rtvec_v (ncases, labelvec),
+						 gen_rtvec_v (ncases, labelvec.address ()),
 						 const0_rtx, const0_rtx));
   else
     emit_jump_table_data (gen_rtx_ADDR_VEC (CASE_VECTOR_MODE,
-					    gen_rtvec_v (ncases, labelvec)));
+					    gen_rtvec_v (ncases, labelvec.address ())));
 
   /* Record no drop-through after the table.  */
   emit_barrier ();
-- 
2.39.0


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