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This patch implements TARGET_COMPARE_VERSION_PRIORITY and
TARGET_OPTION_FUNCTION_VERSIONS for RISC-V.
The TARGET_COMPARE_VERSION_PRIORITY is implemented to compare the
priority of two function versions based on the rules defined in the
RISC-V C-API Doc PR #85:
https://github.com/riscv-non-isa/riscv-c-api-doc/pull/85/files#diff-79a93ca266139524b8b642e582ac20999357542001f1f4666fbb62b6fb7a5824R721
If multiple versions have equal priority, we select the function with
the most number of feature bits generated by
riscv_minimal_hwprobe_feature_bits. When it comes to the same number of
feature bits, we diff two versions and select the one with the least
significant bit set. Since a feature appears earlier in the feature_bits
might be more important to performance.
The TARGET_OPTION_FUNCTION_VERSIONS is implemented to check whether the
two function versions are the same. This Implementation reuses the code
in TARGET_COMPARE_VERSION_PRIORITY and check it returns 0, which means
the equal priority.
Co-Developed-by: Hank Chang <hank.chang@sifive.com>
Signed-off-by: Yangyu Chen <cyy@cyyself.name>
gcc/ChangeLog:
* config/riscv/riscv.cc
(parse_features_for_version): New function.
(compare_fmv_features): New function.
(riscv_compare_version_priority): New function.
(riscv_common_function_versions): New function.
(TARGET_COMPARE_VERSION_PRIORITY): Implement it.
(TARGET_OPTION_FUNCTION_VERSIONS): Implement it.
---
gcc/config/riscv/riscv.cc | 127 ++++++++++++++++++++++++++++++++++++++
1 file changed, 127 insertions(+)
@@ -12686,6 +12686,127 @@ riscv_c_mode_for_floating_type (enum tree_index ti)
return default_mode_for_floating_type (ti);
}
+/* This parses the attribute arguments to target_version in DECL and modifies
+ the feature mask and priority required to select those targets. */
+static void
+parse_features_for_version (tree decl,
+ struct riscv_feature_bits &res,
+ int &priority)
+{
+ tree version_attr = lookup_attribute ("target_version",
+ DECL_ATTRIBUTES (decl));
+ if (version_attr == NULL_TREE)
+ {
+ res.length = 0;
+ priority = 0;
+ return;
+ }
+
+ const char *version_string = TREE_STRING_POINTER (TREE_VALUE (TREE_VALUE
+ (version_attr)));
+ gcc_assert (version_string != NULL);
+ if (strcmp (version_string, "default") == 0)
+ {
+ res.length = 0;
+ priority = 0;
+ return;
+ }
+ struct cl_target_option cur_target;
+ cl_target_option_save (&cur_target, &global_options,
+ &global_options_set);
+ /* Always set to default option before parsing "arch=+..." */
+ struct cl_target_option *default_opts
+ = TREE_TARGET_OPTION (target_option_default_node);
+ cl_target_option_restore (&global_options, &global_options_set,
+ default_opts);
+
+ riscv_process_target_version_attr (TREE_VALUE (version_attr),
+ DECL_SOURCE_LOCATION (decl));
+
+ priority = global_options.x_riscv_fmv_priority;
+ const char *arch_string = global_options.x_riscv_arch_string;
+ bool parse_res
+ = riscv_minimal_hwprobe_feature_bits (arch_string, &res,
+ DECL_SOURCE_LOCATION (decl));
+ gcc_assert (parse_res);
+
+ if (arch_string != default_opts->x_riscv_arch_string)
+ free (CONST_CAST (void *, (const void *) arch_string));
+
+ cl_target_option_restore (&global_options, &global_options_set,
+ &cur_target);
+}
+
+/* Compare priorities of two feature masks. Return:
+ 1: mask1 is higher priority
+ -1: mask2 is higher priority
+ 0: masks are equal.
+ Since riscv_feature_bits has total 128 bits to be used as mask, when counting
+ the total 1s in the mask, the 1s in group1 needs to multiply a weight. */
+static int
+compare_fmv_features (const struct riscv_feature_bits &mask1,
+ const struct riscv_feature_bits &mask2,
+ int prio1, int prio2)
+{
+ unsigned length1 = mask1.length, length2 = mask2.length;
+ /* 1. Compare length, for length == 0 means default version, which should be
+ the lowest priority). */
+ if (length1 != length2)
+ return length1 > length2 ? 1 : -1;
+ /* 2. Compare the priority. */
+ if (prio1 != prio2)
+ return prio1 > prio2 ? 1 : -1;
+ /* 3. Compare the total number of 1s in the mask. */
+ unsigned pop1 = 0, pop2 = 0;
+ for (unsigned i = 0; i < length1; i++)
+ {
+ pop1 += __builtin_popcountll (mask1.features[i]);
+ pop2 += __builtin_popcountll (mask2.features[i]);
+ }
+ if (pop1 != pop2)
+ return pop1 > pop2 ? 1 : -1;
+ /* 4. Compare the mask bit by bit order. */
+ for (unsigned i = 0; i < length1; i++)
+ {
+ unsigned long long xor_mask = mask1.features[i] ^ mask2.features[i];
+ if (xor_mask == 0)
+ continue;
+ return TEST_BIT (mask1.features[i], __builtin_ctzll (xor_mask)) ? 1 : -1;
+ }
+ /* 5. If all bits are equal, return 0. */
+ return 0;
+}
+
+/* Compare priorities of two version decls. Return:
+ 1: mask1 is higher priority
+ -1: mask2 is higher priority
+ 0: masks are equal. */
+int
+riscv_compare_version_priority (tree decl1, tree decl2)
+{
+ struct riscv_feature_bits mask1, mask2;
+ int prio1, prio2;
+
+ parse_features_for_version (decl1, mask1, prio1);
+ parse_features_for_version (decl2, mask2, prio2);
+
+ return compare_fmv_features (mask1, mask2, prio1, prio2);
+}
+
+/* This function returns true if FN1 and FN2 are versions of the same function,
+ that is, the target_version attributes of the function decls are different.
+ This assumes that FN1 and FN2 have the same signature. */
+
+bool
+riscv_common_function_versions (tree fn1, tree fn2)
+{
+ if (TREE_CODE (fn1) != FUNCTION_DECL
+ || TREE_CODE (fn2) != FUNCTION_DECL)
+ return false;
+
+ return riscv_compare_version_priority (fn1, fn2) != 0;
+}
+
/* On riscv we have an ABI defined safe buffer. This constant is used to
determining the probe offset for alloca. */
@@ -13064,6 +13185,12 @@ riscv_stack_clash_protection_alloca_probe_range (void)
#define TARGET_OPTION_VALID_VERSION_ATTRIBUTE_P \
riscv_option_valid_version_attribute_p
+#undef TARGET_COMPARE_VERSION_PRIORITY
+#define TARGET_COMPARE_VERSION_PRIORITY riscv_compare_version_priority
+
+#undef TARGET_OPTION_FUNCTION_VERSIONS
+#define TARGET_OPTION_FUNCTION_VERSIONS riscv_common_function_versions
+
struct gcc_target targetm = TARGET_INITIALIZER;
#include "gt-riscv.h"