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tint: fix extractBits edge case 

If count is highest and offset is non-zero, or vice-versa, we'd overflow
the count + offset > bit-width check. This CL fixes this case.

Bug: tint:1581
Bug: chromium:1381810
Change-Id: I6ee60ec1a13230fca6f4bb6407cd33bcc6730eb7
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/109162
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
This commit is contained in:
Antonio Maiorano 2022-11-08 18:27:08 +00:00 committed by Dawn LUCI CQ
parent 0a7364815c
commit a70e365313
2 changed files with 9 additions and 7 deletions
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14
src/tint/resolver/const_eval.cc
View File

@ -1901,18 +1901,18 @@ ConstEval::Result ConstEval::extractBits(const sem::Type* ty,
NumberUT in_offset = args[1]->As<NumberUT>();
NumberUT in_count = args[2]->As<NumberUT>();
constexpr UT w = sizeof(UT) * 8;
if ((in_offset + in_count) > w) {
AddError("'offset + 'count' must be less than or equal to the bit width of 'e'",
source);
return utils::Failure;
}
// Cast all to unsigned
UT e = static_cast<UT>(in_e);
UT o = static_cast<UT>(in_offset);
UT c = static_cast<UT>(in_count);
constexpr UT w = sizeof(UT) * 8;
if (o > w || c > w || (o + c) > w) {
AddError("'offset + 'count' must be less than or equal to the bit width of 'e'",
source);
return utils::Failure;
}
NumberT result;
if (c == UT{0}) {
// The result is 0 if c is 0

2
src/tint/resolver/const_eval_builtin_test.cc
View File

@ -1226,6 +1226,8 @@ INSTANTIATE_TEST_SUITE_P(ExtractBits,
std::make_tuple(33, 33), //
std::make_tuple(34, 34), //
std::make_tuple(1000, 1000), //
std::make_tuple(u32::Highest(), 1), //
std::make_tuple(1, u32::Highest()), //
std::make_tuple(u32::Highest(), u32::Highest())));
std::vector<Case> Pack4x8snormCases() {