On 08/18/2016 04:45 PM, Ilia Mirkin wrote:
Since it *is* a hash, you could just use a much simpler hash function like
int hash(int val) {
int ret = val + 1000;
if (ret == 0) ret = 1;
return ret;
}
That way everything will map to a unique integer, except for -1000
which will map to the same thing as -999. I posit that this should be
rare, and hash collisions are perfectly fine in any case (it's not
like we have 1<<32 buckets anyways). This also avoids the zero hash
value case.
IMO this is fine, I originally had something along the lines of this but
then I thought using hash_data would be more 'elegant way' to create
unique values. I will check Eric's proposal also.
-ilia
On Thu, Aug 18, 2016 at 7:52 AM, Ilia Mirkin <[email protected]> wrote:
Can the hash value not be 0?
On Aug 18, 2016 4:57 AM, "Tapani Pälli" <[email protected]> wrote:
Implementation previously used case value itself as the key, however
afterhash implementation change by ee02a5e we cannot use 0 as key.
Patch uses _mesa_hash_data to formulate a suitable key for this hash.
Signed-off-by: Tapani Pälli <[email protected]>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97309
---
src/compiler/glsl/ast_to_hir.cpp | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/src/compiler/glsl/ast_to_hir.cpp
b/src/compiler/glsl/ast_to_hir.cpp
index e03a6e3..53fc4d6 100644
--- a/src/compiler/glsl/ast_to_hir.cpp
+++ b/src/compiler/glsl/ast_to_hir.cpp
@@ -6180,9 +6180,11 @@ ast_case_label::hir(exec_list *instructions,
/* Stuff a dummy value in to allow processing to continue. */
label_const = new(ctx) ir_constant(0);
} else {
+ unsigned hash_key = _mesa_hash_data(&label_const->value.u[0],
+ sizeof(unsigned));
ast_expression *previous_label = (ast_expression *)
hash_table_find(state->switch_state.labels_ht,
- (void *)(uintptr_t)label_const->value.u[0]);
+ (void *)(uintptr_t)hash_key);
if (previous_label) {
YYLTYPE loc = this->test_value->get_location();
@@ -6193,7 +6195,7 @@ ast_case_label::hir(exec_list *instructions,
} else {
hash_table_insert(state->switch_state.labels_ht,
this->test_value,
- (void
*)(uintptr_t)label_const->value.u[0]);
+ (void *)(uintptr_t)hash_key);
}
}
--
2.5.5
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