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Merged
s-perron merged 1 commit into from
Feb 6, 2026
+157 −30
Merged

spirv-opt: handle mixed-width shifts in RedundantAndShift #6504

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84 changes: 57 additions & 27 deletions source/opt/folding_rules.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3312,45 +3312,75 @@ FoldingRule RedundantAndShift() {
const analysis::Type* type =
context->get_type_mgr()->GetType(inst->type_id());
uint32_t width = ElementWidth(type);
if ((width != 32) && (width != 64)) return false;
if (width != 8 && width != 16 && width != 32 && width != 64) return false;
const uint64_t width_mask =
(width == 64) ? ~0ull : ((1ull << width) - 1ull);

analysis::ConstantManager* const_mgr = context->get_constant_mgr();
const analysis::Constant* const_input1 = ConstInput(constants);
if (!const_input1) return false;
Instruction* other_inst = NonConstInput(context, constants[0], inst);

spv::Op other_op = other_inst->opcode();
if (other_op == spv::Op::OpShiftLeftLogical ||
other_op == spv::Op::OpShiftRightLogical) {
std::vector<const analysis::Constant*> other_constants =
const_mgr->GetOperandConstants(other_inst);
if (other_op != spv::Op::OpShiftLeftLogical &&
other_op != spv::Op::OpShiftRightLogical) {
return false;
}

// Only valid if const is on the right
if (other_constants[0]) {
return false;
}
const analysis::Constant* const_input2 = other_constants[1];
if (!const_input2) return false;
std::vector<const analysis::Constant*> other_constants =
const_mgr->GetOperandConstants(other_inst);

bool can_convert_to_zero = true;
ForEachIntegerConstantPair(
const_mgr, const_input1, const_input2,
[&can_convert_to_zero, other_op](auto lhs, auto rhs) {
if (other_op == spv::Op::OpShiftRightLogical) {
can_convert_to_zero = can_convert_to_zero && (lhs << rhs) == 0;
} else {
can_convert_to_zero = can_convert_to_zero && (lhs >> rhs) == 0;
}
});
// Only valid if const is on the right.
if (other_constants[0]) return false;
const analysis::Constant* const_input2 = other_constants[1];
if (!const_input2) return false;

if (can_convert_to_zero) {
auto zero_id = context->get_constant_mgr()->GetNullConstId(type);
inst->SetOpcode(spv::Op::OpCopyObject);
inst->SetInOperands({{SPV_OPERAND_TYPE_ID, {zero_id}}});
return true;
auto get_value_u64 =
[](const analysis::Constant* c) -> std::optional<uint64_t> {
if (!c) return std::nullopt;
const analysis::Integer* int_t = c->type()->AsInteger();
if (!int_t) return std::nullopt;
return c->GetZeroExtendedValue();
};

auto can_fold_component =
[&](const analysis::Constant* mask_const,
const analysis::Constant* shift_const) -> std::optional<bool> {
auto lhs = get_value_u64(mask_const);
auto rhs = get_value_u64(shift_const);
if (!lhs || !rhs) return std::nullopt;
if (*rhs >= width) return false;
uint64_t lhs_masked = *lhs & width_mask;
if (other_op == spv::Op::OpShiftRightLogical) {
return ((lhs_masked << *rhs) & width_mask) == 0;
}
return ((lhs_masked >> *rhs) & width_mask) == 0;
};

if (const analysis::Vector* mask_vec = type->AsVector()) {
const analysis::Vector* shift_vec = const_input2->type()->AsVector();
if (!shift_vec ||
shift_vec->element_count() != mask_vec->element_count()) {
return false;
}
const auto mask_components = const_input1->GetVectorComponents(const_mgr);
const auto shift_components =
const_input2->GetVectorComponents(const_mgr);
for (uint32_t i = 0; i != mask_vec->element_count(); ++i) {
auto result =
can_fold_component(mask_components[i], shift_components[i]);
if (!result || !*result) return false;
}
} else {
if (const_input2->type()->AsVector()) return false;
auto result = can_fold_component(const_input1, const_input2);
if (!result || !*result) return false;
}
return false;

auto zero_id = context->get_constant_mgr()->GetNullConstId(type);
inst->SetOpcode(spv::Op::OpCopyObject);
inst->SetInOperands({{SPV_OPERAND_TYPE_ID, {zero_id}}});
return true;
};
}

Expand Down
103 changes: 100 additions & 3 deletions test/opt/fold_test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -211,6 +211,10 @@ TEST_P(IntegerInstructionFoldingTest, Case) {
#define UINT_0_ID 109
#define INT_NULL_ID 110
#define UINT_NULL_ID 111
#define ULONG_NULL_ID 120
#define UBYTE_NULL_ID 121
#define USHORT_NULL_ID 122
#define V2USHORT_NULL_ID 123
#define HALF_3_ID 112
#define FLOAT_NULL_ID 113
const std::string& Header() {
Expand Down Expand Up @@ -280,6 +284,8 @@ OpName %main "main"
%_ptr_half = OpTypePointer Function %half
%_ptr_long = OpTypePointer Function %long
%_ptr_ulong = OpTypePointer Function %ulong
%_ptr_ubyte = OpTypePointer Function %ubyte
%_ptr_ushort = OpTypePointer Function %ushort
%_ptr_v2int = OpTypePointer Function %v2int
%_ptr_v4int = OpTypePointer Function %v4int
%_ptr_v4float = OpTypePointer Function %v4float
Expand All @@ -288,6 +294,7 @@ OpName %main "main"
%_ptr_struct_v2int_int_int = OpTypePointer Function %struct_v2int_int_int
%_ptr_v2float = OpTypePointer Function %v2float
%_ptr_v2double = OpTypePointer Function %v2double
%_ptr_v2ushort = OpTypePointer Function %v2ushort
%int_2 = OpConstant %int 2
%int_arr_2 = OpTypeArray %int %int_2
%short_n1 = OpConstant %short -1
Expand All @@ -306,7 +313,7 @@ OpName %main "main"
%ushort_1 = OpConstant %ushort 1
%ushort_2 = OpConstant %ushort 2
%ushort_3 = OpConstant %ushort 3
%ushort_null = OpConstantNull %ushort
%122 = OpConstantNull %ushort ; Need a def with an numerical id to define id maps.
%100 = OpConstant %int 0 ; Need a def with an numerical id to define id maps.
%110 = OpConstantNull %int ; Need a def with an numerical id to define id maps.
%103 = OpConstant %int 7 ; Need a def with an numerical id to define id maps.
Expand Down Expand Up @@ -341,6 +348,9 @@ OpName %main "main"
%ulong_4611686018427387904 = OpConstant %ulong 4611686018427387904
%109 = OpConstant %uint 0 ; Need a def with an numerical id to define id maps.
%111 = OpConstantNull %uint ; Need a def with an numerical id to define id maps.
%120 = OpConstantNull %ulong ; Need a def with an numerical id to define id maps.
%121 = OpConstantNull %ubyte ; Need a def with an numerical id to define id maps.
%123 = OpConstantNull %v2ushort ; Need a def with an numerical id to define id maps.
%uint_0 = OpConstant %uint 0
%uint_1 = OpConstant %uint 1
%uint_2 = OpConstant %uint 2
Expand Down Expand Up @@ -463,7 +473,7 @@ OpName %main "main"
%v4uint_1_0x0000ffff_uint_0_uint_max = OpConstantComposite %v4uint %uint_1 %uint_0x0000ffff %uint_0 %uint_max
%v2uint_1_null = OpConstantComposite %v2uint %uint_1 %111
%v2uint_null = OpConstantNull %v2uint
%v2ushort_1_null = OpConstantComposite %v2ushort %ushort_1 %ushort_null
%v2ushort_1_null = OpConstantComposite %v2ushort %ushort_1 %122
%v4ushort_0_1_2_3 = OpConstantComposite %v4ushort %ushort_0 %ushort_1 %ushort_2 %ushort_3
%v2ubyte_a_b = OpConstantComposite %v2ubyte %ubyte_a %ubyte_b
%v4ubyte_a_b_c_d = OpConstantComposite %v4ubyte %ubyte_a %ubyte_b %ubyte_c %ubyte_d
Expand Down Expand Up @@ -9419,7 +9429,94 @@ INSTANTIATE_TEST_SUITE_P(RedundantAndAddSubTest, MatchingInstructionFoldingTest,
"%2 = OpBitwiseAnd %uint %uint_4026531841 %3\n" +
"OpReturn\n" +
"OpFunctionEnd",
2, 0)
2, 0),

// Test case 15: Fold (mixed-width shift amount)
// 1u64 & (n << 1u32) = 0
InstructionFoldingCase<uint32_t>(
Header() +
"%main = OpFunction %void None %void_func\n" +
"%main_lab = OpLabel\n" +
"%n = OpVariable %_ptr_ulong Function\n" +
"%4 = OpLoad %ulong %n\n" +
"%3 = OpShiftLeftLogical %ulong %4 %uint_1\n" +
"%2 = OpBitwiseAnd %ulong %ulong_1 %3\n" +
"OpReturn\n" +
"OpFunctionEnd",
2, ULONG_NULL_ID),

// Test case 16: Fold (8-bit base, 32-bit shift amount)
// 1u8 & (n << 1u32) = 0
InstructionFoldingCase<uint32_t>(
Header() +
"%main = OpFunction %void None %void_func\n" +
"%main_lab = OpLabel\n" +
"%n = OpVariable %_ptr_ubyte Function\n" +
"%4 = OpLoad %ubyte %n\n" +
"%3 = OpShiftLeftLogical %ubyte %4 %uint_1\n" +
"%2 = OpBitwiseAnd %ubyte %ubyte_1 %3\n" +
"OpReturn\n" +
"OpFunctionEnd",
2, UBYTE_NULL_ID),

// Test case 17: Fold (16-bit base, 32-bit shift amount)
// 1u16 & (n << 1u32) = 0
InstructionFoldingCase<uint32_t>(
Header() +
"%main = OpFunction %void None %void_func\n" +
"%main_lab = OpLabel\n" +
"%n = OpVariable %_ptr_ushort Function\n" +
"%4 = OpLoad %ushort %n\n" +
"%3 = OpShiftLeftLogical %ushort %4 %uint_1\n" +
"%2 = OpBitwiseAnd %ushort %ushort_1 %3\n" +
"OpReturn\n" +
"OpFunctionEnd",
2, USHORT_NULL_ID),

// Test case 18: Fold (vector, mixed-width shift amount)
// <1,0>u16 & (n << <1,0>u32) = 0
InstructionFoldingCase<uint32_t>(
Header() +
"%main = OpFunction %void None %void_func\n" +
"%main_lab = OpLabel\n" +
"%n = OpVariable %_ptr_v2ushort Function\n" +
"%4 = OpLoad %v2ushort %n\n" +
"%3 = OpShiftLeftLogical %v2ushort %4 %v2uint_1_null\n" +
"%2 = OpBitwiseAnd %v2ushort %v2ushort_1_null %3\n" +
"OpReturn\n" +
"OpFunctionEnd",
2, V2USHORT_NULL_ID),

// Test case 19: Fold (8-bit base, 32-bit shift amount, right shift)
// 0x80u8 & (n >> 1u32) = 0
InstructionFoldingCase<uint32_t>(
Header() +
"%ubyte_128 = OpConstant %ubyte 128\n" +
"%main = OpFunction %void None %void_func\n" +
"%main_lab = OpLabel\n" +
"%n = OpVariable %_ptr_ubyte Function\n" +
"%4 = OpLoad %ubyte %n\n" +
"%3 = OpShiftRightLogical %ubyte %4 %uint_1\n" +
"%2 = OpBitwiseAnd %ubyte %ubyte_128 %3\n" +
"OpReturn\n" +
"OpFunctionEnd",
2, UBYTE_NULL_ID),

// Test case 20: Fold (vector, mixed-width shift amount, right shift)
// <0x8000,0>u16 & (n >> <1,0>u32) = 0
InstructionFoldingCase<uint32_t>(
Header() +
"%ushort_32768 = OpConstant %ushort 32768\n" +
"%v2ushort_32768_0 = OpConstantComposite %v2ushort %ushort_32768 %ushort_0\n" +
"%main = OpFunction %void None %void_func\n" +
"%main_lab = OpLabel\n" +
"%n = OpVariable %_ptr_v2ushort Function\n" +
"%4 = OpLoad %v2ushort %n\n" +
"%3 = OpShiftRightLogical %v2ushort %4 %v2uint_1_null\n" +
"%2 = OpBitwiseAnd %v2ushort %v2ushort_32768_0 %3\n" +
"OpReturn\n" +
"OpFunctionEnd",
2, V2USHORT_NULL_ID)
));

INSTANTIATE_TEST_SUITE_P(MergeAddTest, MatchingInstructionFoldingTest,
Expand Down