{"id":2233382,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2233382/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/20260506041649.1357118-1-naveen.siddegowda@oss.qualcomm.com/","project":{"id":17,"url":"http://patchwork.ozlabs.org/api/1.1/projects/17/?format=json","name":"GNU Compiler Collection","link_name":"gcc","list_id":"gcc-patches.gcc.gnu.org","list_email":"gcc-patches@gcc.gnu.org","web_url":null,"scm_url":null,"webscm_url":null},"msgid":"<20260506041649.1357118-1-naveen.siddegowda@oss.qualcomm.com>","date":"2026-05-06T04:16:49","name":"tree-optimization: fold memset with length in [0, 1] to conditional store [PR102202]","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"eb42a8e62ce96dc943e404ca7987ff1967e10817","submitter":{"id":93028,"url":"http://patchwork.ozlabs.org/api/1.1/people/93028/?format=json","name":"Naveen","email":"naveen.siddegowda@oss.qualcomm.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/gcc/patch/20260506041649.1357118-1-naveen.siddegowda@oss.qualcomm.com/mbox/","series":[{"id":502957,"url":"http://patchwork.ozlabs.org/api/1.1/series/502957/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=502957","date":"2026-05-06T04:16:49","name":"tree-optimization: fold memset with length in [0, 1] to conditional store [PR102202]","version":1,"mbox":"http://patchwork.ozlabs.org/series/502957/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2233382/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2233382/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","gcc-patches@gcc.gnu.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","gcc-patches@gcc.gnu.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=fail reason=\"signature verification failed\" (2048-bit key;\n unprotected) header.d=qualcomm.com header.i=@qualcomm.com header.a=rsa-sha256\n header.s=qcppdkim1 header.b=AXqibMJi;\n\tdkim=fail reason=\"signature verification failed\" (2048-bit key;\n unprotected) header.d=oss.qualcomm.com header.i=@oss.qualcomm.com\n header.a=rsa-sha256 header.s=google header.b=ku99eSl+;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=38.145.34.32; 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","Errors-To":"gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org"},"content":"PR tree-optimization/102202\n\ngcc/ChangeLog:\n\n\tPR tree-optimization/102202\n\t* tree-call-cdce.cc: Include \"tree-ssanames.h\", \"gimple-fold.h\"\n\tand \"gimplify-me.h\".\n\t(memset_len_zero_or_one_p): New function.\n\t(can_shrink_wrap_memset_p): New function.\n\t(gen_memset_conditions): New function.\n\t(replace_memset_call_with_store): New function.\n\t(shrink_wrap_one_memset_call): New function.\n\t(shrink_wrap_conditional_dead_built_in_calls): Dispatch to\n\tshrink_wrap_one_memset_call for memset calls eligible for the [0, 1]\n\tlength transform, ahead of the generic LHS and range-test paths.\n\t(pass_call_cdce::execute): Collect memset calls satisfying\n\tcan_shrink_wrap_memset_p as shrink-wrap candidates.\n\ngcc/testsuite/ChangeLog:\n\n\t* gcc.dg/pr102202.c: New test.\n\nSigned-off-by: Naveen \n---\n gcc/testsuite/gcc.dg/pr102202.c | 31 +++++++\n gcc/tree-call-cdce.cc | 138 +++++++++++++++++++++++++++++++-\n 2 files changed, 165 insertions(+), 4 deletions(-)\n create mode 100644 gcc/testsuite/gcc.dg/pr102202.c","diff":"diff --git a/gcc/testsuite/gcc.dg/pr102202.c b/gcc/testsuite/gcc.dg/pr102202.c\nnew file mode 100644\nindex 00000000000..6d3306370c0\n--- /dev/null\n+++ b/gcc/testsuite/gcc.dg/pr102202.c\n@@ -0,0 +1,31 @@\n+/* PR tree-optimization/102202 */\n+/* { dg-do compile } */\n+/* { dg-options \"-O2 -fdump-tree-optimized\" } */\n+\n+void\n+g1 (int a, char *d)\n+{\n+ if (a < 0 || a > 1)\n+ __builtin_unreachable ();\n+ __builtin_memset (d, 0, a);\n+}\n+\n+char *\n+g2 (unsigned a, char *d)\n+{\n+ return __builtin_memset (d, 1, a & 1);\n+}\n+\n+void\n+g3 (int a, int c, char *d)\n+{\n+ if (a < 0 || a > 1)\n+ __builtin_unreachable ();\n+ __builtin_memset (d, c, a);\n+}\n+\n+/* { dg-final { scan-tree-dump-times {MEM[^;\\n]*= 0;} 1 \"optimized\" } } */\n+/* { dg-final { scan-tree-dump-times {MEM[^;\\n]*= 1;} 1 \"optimized\" } } */\n+/* { dg-final { scan-tree-dump-times {return d_[0-9]} 1 \"optimized\" } } */\n+/* { dg-final { scan-tree-dump-times {MEM[^;\\n]*=.*c_[0-9]+\\(D\\)} 1 \"optimized\" } } */\n+/* { dg-final { scan-tree-dump-not \"MEMSET\" \"optimized\" } } */\ndiff --git a/gcc/tree-call-cdce.cc b/gcc/tree-call-cdce.cc\nindex 2be891a7222..6e4ebd00765 100644\n--- a/gcc/tree-call-cdce.cc\n+++ b/gcc/tree-call-cdce.cc\n@@ -37,6 +37,9 @@ along with GCC; see the file COPYING3. If not see\n #include \"internal-fn.h\"\n #include \"tree-dfa.h\"\n #include \"tree-eh.h\"\n+#include \"tree-ssanames.h\"\n+#include \"gimple-fold.h\"\n+#include \"gimplify-me.h\"\n \f\n \n /* This pass serves two closely-related purposes:\n@@ -1255,9 +1258,130 @@ use_internal_fn (gcall *call)\n \t\t\t\t\t is_arg_conds ? new_call : NULL);\n }\n \n+/* Return true if LEN is a constant zero or one or an SSA_NAME known to have\n+ a boolean range. */\n+\n+static bool\n+memset_len_zero_or_one_p (tree len, gimple *stmt)\n+{\n+ if (integer_zerop (len) || integer_onep (len))\n+ return true;\n+\n+ if (TREE_CODE (len) != SSA_NAME || !INTEGRAL_TYPE_P (TREE_TYPE (len)))\n+ return false;\n+ return ssa_name_has_boolean_range (len, stmt);\n+}\n+\n+/* Return true if CALL is a memset that may be shrink-wrapped based on LEN\n+ being known to be zero or one. */\n+\n+static bool\n+can_shrink_wrap_memset_p (gcall *call)\n+{\n+ tree fndecl = gimple_call_fndecl (call);\n+\n+ if (!fndecl\n+ || !fndecl_built_in_p (fndecl, BUILT_IN_NORMAL)\n+ || DECL_FUNCTION_CODE (fndecl) != BUILT_IN_MEMSET)\n+ return false;\n+\n+ /* The replacement store needs to preserve the original memory VDEF. */\n+ if (!gimple_vdef (call))\n+ return false;\n+\n+ return memset_len_zero_or_one_p (gimple_call_arg (call, 2), call);\n+}\n+\n+/* Generate the condition vector used to guard a memset call whose length is\n+ known to be in [0, 1]. */\n+\n+static void\n+gen_memset_conditions (gcall *call, vec &conds, unsigned *nconds)\n+{\n+ tree len = gimple_call_arg (call, 2);\n+ tree zero = build_zero_cst (TREE_TYPE (len));\n+\n+ gcc_assert (nconds);\n+ *nconds = 0;\n+\n+ conds.quick_push (gimple_build_cond (EQ_EXPR, len, zero,\n+\t\t\t\t NULL_TREE, NULL_TREE));\n+ *nconds = 1;\n+}\n+\n+/* Replace CALL known to be a length-one memset with a single-byte store.\n+ The destination is converted to unsigned char * and the fill value to the\n+ destination byte type using gimple_convert. */\n+\n+static void\n+replace_memset_call_with_store (gcall *call)\n+{\n+ tree dest = gimple_call_arg (call, 0);\n+ tree c = gimple_call_arg (call, 1);\n+ location_t loc = gimple_location (call);\n+\n+ tree byte_type = unsigned_char_type_node;\n+ tree byte_ptr_type = build_pointer_type (byte_type);\n+\n+ gimple_stmt_iterator gsi = gsi_for_stmt (call);\n+ dest = gimple_convert (&gsi, true, GSI_SAME_STMT, loc, byte_ptr_type, dest);\n+ dest = force_gimple_operand_gsi_1 (&gsi, dest, is_gimple_mem_ref_addr,\n+\t\t\t\t NULL_TREE, true, GSI_SAME_STMT);\n+\n+ tree mem = build2 (MEM_REF, byte_type, dest,\n+\t\t build_int_cst (ptr_type_node, 0));\n+\n+ /* Memset writes the low byte of the fill value to each destination type. */\n+ tree rhs = gimple_convert (&gsi, true, GSI_SAME_STMT, loc, byte_type, c);\n+\n+ gassign *store = gimple_build_assign (mem, rhs);\n+ gimple_move_vops (store, call);\n+ gimple_set_location (store, loc);\n+\n+ copy_warning (store, call);\n+ suppress_warning (store, OPT_Wstringop_overflow_);\n+\n+ gsi = gsi_for_stmt (call);\n+ gsi_replace (&gsi, store, false);\n+}\n+\n+/* Shrink wrap a memset call whose length is known to be in [0, 1].\n+ If the call has an LHS, preserve the builtin return value by assigning the\n+ destination pointer to the LHS before the call transfer. */\n+\n+static void\n+shrink_wrap_one_memset_call (gcall *call)\n+{\n+ tree lhs = gimple_call_lhs (call);\n+\n+ if (lhs)\n+ {\n+ tree dest = gimple_call_arg (call, 0);\n+ location_t loc = gimple_location (call);\n+ gimple_stmt_iterator gsi = gsi_for_stmt (call);\n+\n+ dest = gimple_convert (&gsi, true, GSI_SAME_STMT, loc,\n+\t\t\t TREE_TYPE (lhs), dest);\n+ gassign *stmt = gimple_build_assign (lhs, dest);\n+ gimple_set_location (stmt, loc);\n+\n+ gsi_insert_before (&gsi, stmt, GSI_SAME_STMT);\n+\n+ gimple_call_set_lhs (call, NULL_TREE);\n+ SSA_NAME_DEF_STMT (lhs) = stmt;\n+ }\n+\n+ unsigned nconds = 0;\n+ auto_vec conds;\n+ gen_memset_conditions (call, conds, &nconds);\n+ gcc_assert (nconds != 0);\n+\n+ shrink_wrap_one_built_in_call_with_conds (call, conds, nconds);\n+ replace_memset_call_with_store (call);\n+}\n+\n /* The top level function for conditional dead code shrink\n wrapping transformation. */\n-\n static void\n shrink_wrap_conditional_dead_built_in_calls (const vec &calls)\n {\n@@ -1267,8 +1391,13 @@ shrink_wrap_conditional_dead_built_in_calls (const vec &calls)\n for (; i < n ; i++)\n {\n gcall *bi_call = calls[i];\n- if (gimple_call_lhs (bi_call))\n+\n+ /* Use the memset specific transform for the [0, 1] length case. */\n+ if (can_shrink_wrap_memset_p (bi_call))\n+\tshrink_wrap_one_memset_call (bi_call);\n+ else if (gimple_call_lhs (bi_call))\n \tuse_internal_fn (bi_call);\n+ /* Other eligible calls are shrink wrapped by the generic path. */\n else\n \tshrink_wrap_one_built_in_call (bi_call);\n }\n@@ -1328,9 +1457,10 @@ pass_call_cdce::execute (function *fun)\n \t gcall *stmt = dyn_cast (gsi_stmt (i));\n if (stmt\n \t && gimple_call_builtin_p (stmt, BUILT_IN_NORMAL)\n-\t && (gimple_call_lhs (stmt)\n+\t && (can_shrink_wrap_memset_p (stmt)\n+\t || (gimple_call_lhs (stmt)\n \t\t ? can_use_internal_fn (stmt)\n-\t\t : can_test_argument_range (stmt))\n+\t\t : can_test_argument_range (stmt)))\n \t && can_guard_call_p (stmt))\n {\n if (dump_file && (dump_flags & TDF_DETAILS))\n","prefixes":[]}