x86: Build only one __cpu_model/__cpu_features2 variables
GCC -O2 generated quite bad code for this function:
bool
f (void)
{
return __builtin_cpu_supports("popcnt")
&& __builtin_cpu_supports("ssse3");
}
f:
movl __cpu_model+12(%rip), %edx
movl %edx, %eax
shrl $6, %eax
andl $1, %eax
andl $4, %edx
movl $0, %edx
cmove %edx, %eax
ret
The problem was caused by the fact that internally every invocation of
__builtin_cpu_supports built a new variable __cpu_model and a new type
__processor_model. Because of this, GIMPLE level optimizers weren't able
to CSE the loads of __cpu_model and optimize bit-operations properly.
Improve GCC -O2 code generation by caching __cpu_model and__cpu_features2
variables as well as their types:
f:
movl __cpu_model+12(%rip), %eax
andl $68, %eax
cmpl $68, %eax
sete %al
ret
2021-05-05 Ivan Sorokin <vanyacpp@gmail.com>
H.J. Lu <hjl.tools@gmail.com>
gcc/
PR target/91400
* config/i386/i386-builtins.c (ix86_cpu_model_type_node): New.
(ix86_cpu_model_var): Likewise.
(ix86_cpu_features2_type_node): Likewise.
(ix86_cpu_features2_var): Likewise.
(fold_builtin_cpu): Cache __cpu_model and __cpu_features2 with
their types.
gcc/testsuite/
PR target/91400
* gcc.target/i386/pr91400-1.c: New test.
* gcc.target/i386/pr91400-2.c: Likewise.
This commit is contained in:
Ivan Sorokin
H.J. Lu
parent
2254b3233b
commit
a0b4e09ab0
3 changed files with 63 additions and 17 deletions
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@ -2103,6 +2103,11 @@ make_var_decl (tree type, const char *name)
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return new_decl;
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}
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static GTY(()) tree ix86_cpu_model_type_node;
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static GTY(()) tree ix86_cpu_model_var;
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static GTY(()) tree ix86_cpu_features2_type_node;
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static GTY(()) tree ix86_cpu_features2_var;
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/* FNDECL is a __builtin_cpu_is or a __builtin_cpu_supports call that is folded
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into an integer defined in libgcc/config/i386/cpuinfo.c */
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@ -2114,12 +2119,16 @@ fold_builtin_cpu (tree fndecl, tree *args)
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= (enum ix86_builtins) DECL_MD_FUNCTION_CODE (fndecl);
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tree param_string_cst = NULL;
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tree __processor_model_type = build_processor_model_struct ();
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tree __cpu_model_var = make_var_decl (__processor_model_type,
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"__cpu_model");
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varpool_node::add (__cpu_model_var);
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if (ix86_cpu_model_var == nullptr)
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{
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/* Build a single __cpu_model variable for all references to
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__cpu_model so that GIMPLE level optimizers can CSE the loads
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of __cpu_model and optimize bit-operations properly. */
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ix86_cpu_model_type_node = build_processor_model_struct ();
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ix86_cpu_model_var = make_var_decl (ix86_cpu_model_type_node,
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"__cpu_model");
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varpool_node::add (ix86_cpu_model_var);
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}
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gcc_assert ((args != NULL) && (*args != NULL));
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@ -2160,7 +2169,7 @@ fold_builtin_cpu (tree fndecl, tree *args)
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return integer_zero_node;
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}
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field = TYPE_FIELDS (__processor_model_type);
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field = TYPE_FIELDS (ix86_cpu_model_type_node);
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field_val = processor_alias_table[i].model;
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/* CPU types are stored in the next field. */
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@ -2179,7 +2188,7 @@ fold_builtin_cpu (tree fndecl, tree *args)
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}
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/* Get the appropriate field in __cpu_model. */
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ref = build3 (COMPONENT_REF, TREE_TYPE (field), __cpu_model_var,
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ref = build3 (COMPONENT_REF, TREE_TYPE (field), ix86_cpu_model_var,
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field, NULL_TREE);
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/* Check the value. */
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@ -2212,13 +2221,22 @@ fold_builtin_cpu (tree fndecl, tree *args)
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if (isa_names_table[i].feature >= 32)
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{
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tree index_type
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= build_index_type (size_int (SIZE_OF_CPU_FEATURES));
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tree type = build_array_type (unsigned_type_node, index_type);
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tree __cpu_features2_var = make_var_decl (type,
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"__cpu_features2");
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if (ix86_cpu_features2_var == nullptr)
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{
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/* Build a single __cpu_features2 variable for all
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references to __cpu_features2 so that GIMPLE level
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optimizers can CSE the loads of __cpu_features2 and
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optimize bit-operations properly. */
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tree index_type
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= build_index_type (size_int (SIZE_OF_CPU_FEATURES));
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ix86_cpu_features2_type_node
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= build_array_type (unsigned_type_node, index_type);
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ix86_cpu_features2_var
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= make_var_decl (ix86_cpu_features2_type_node,
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"__cpu_features2");
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varpool_node::add (ix86_cpu_features2_var);
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}
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varpool_node::add (__cpu_features2_var);
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for (unsigned int j = 0; j < SIZE_OF_CPU_FEATURES; j++)
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if (isa_names_table[i].feature < (32 + 32 + j * 32))
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{
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@ -2226,7 +2244,7 @@ fold_builtin_cpu (tree fndecl, tree *args)
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- (32 + j * 32)));
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tree index = size_int (j);
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array_elt = build4 (ARRAY_REF, unsigned_type_node,
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__cpu_features2_var,
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ix86_cpu_features2_var,
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index, NULL_TREE, NULL_TREE);
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/* Return __cpu_features2[index] & field_val */
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final = build2 (BIT_AND_EXPR, unsigned_type_node,
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@ -2237,13 +2255,13 @@ fold_builtin_cpu (tree fndecl, tree *args)
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}
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}
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field = TYPE_FIELDS (__processor_model_type);
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field = TYPE_FIELDS (ix86_cpu_model_type_node);
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/* Get the last field, which is __cpu_features. */
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while (DECL_CHAIN (field))
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field = DECL_CHAIN (field);
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/* Get the appropriate field: __cpu_model.__cpu_features */
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ref = build3 (COMPONENT_REF, TREE_TYPE (field), __cpu_model_var,
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ref = build3 (COMPONENT_REF, TREE_TYPE (field), ix86_cpu_model_var,
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field, NULL_TREE);
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/* Access the 0th element of __cpu_features array. */
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14
gcc/testsuite/gcc.target/i386/pr91400-1.c
Normal file
14
gcc/testsuite/gcc.target/i386/pr91400-1.c
Normal file
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@ -0,0 +1,14 @@
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/* PR target/91400 */
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/* { dg-do compile } */
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/* { dg-options "-O2" } */
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/* { dg-final { scan-assembler-times "andl" 1 } } */
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/* { dg-final { scan-assembler-times "cmpl" 1 } } */
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/* { dg-final { scan-assembler-times "sete" 1 } } */
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/* { dg-final { scan-assembler-not "cmove" } } */
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_Bool
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f (void)
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{
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return __builtin_cpu_supports("popcnt")
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&& __builtin_cpu_supports("ssse3");
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}
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14
gcc/testsuite/gcc.target/i386/pr91400-2.c
Normal file
14
gcc/testsuite/gcc.target/i386/pr91400-2.c
Normal file
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@ -0,0 +1,14 @@
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/* PR target/91400 */
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/* { dg-do compile } */
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/* { dg-options "-O2" } */
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/* { dg-final { scan-assembler-times "andl" 1 } } */
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/* { dg-final { scan-assembler-times "cmpl" 1 } } */
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/* { dg-final { scan-assembler-times "sete" 1 } } */
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/* { dg-final { scan-assembler-not "cmove" } } */
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_Bool
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f (void)
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{
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return __builtin_cpu_supports("avx512vnni")
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&& __builtin_cpu_supports("3dnow");
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}
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