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SPIR-V: Preliminary integer constant encoding

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This commit is contained in:
Robin Voetter
2021-05-20 02:56:20 +02:00
parent c190b2ff83
commit b8444d2c51
1 changed files with 36 additions and 2 deletions
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38
src/codegen/spirv.zig
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@@ -264,6 +264,40 @@ pub const DeclGen = struct {
}
switch (ty.zigTypeTag()) {
.Int => {
const int_info = ty.intInfo(target);
const backing_bits = self.backingIntBits(int_info.bits) orelse {
// Integers too big for any native type are represented as "composite integers": An array of largestSupportedIntBits.
return self.fail(.{ .node_offset = 0 }, "TODO: SPIR-V backend: implement composite int constants for {}", .{ty});
};
// We can just use toSignedInt/toUnsignedInt here as it returns u64 - a type large enough to hold any
// SPIR-V native type (up to i/u64 with Int64). If SPIR-V ever supports native ints of a larger size, this
// might need to be updated.
std.debug.assert(self.largestSupportedIntBits() <= std.meta.bitCount(u64));
var int_bits = if (ty.isSignedInt()) @bitCast(u64, val.toSignedInt()) else val.toUnsignedInt();
// Mask the low bits which make up the actual integer. This is to make sure that negative values
// only use the actual bits of the type.
// TODO: Should this be the backing type bits or the actual type bits?
int_bits &= (@as(u64, 1) << @intCast(u6, backing_bits)) - 1;
switch (backing_bits) {
0 => unreachable,
1...32 => try writeInstruction(code, .OpConstant, &[_]Word{
result_type_id,
result_id,
@truncate(u32, int_bits),
}),
33...64 => try writeInstruction(code, .OpConstant, &[_]Word{
result_type_id,
result_id,
@truncate(u32, int_bits),
@truncate(u32, int_bits >> @bitSizeOf(u32)),
}),
else => unreachable, // backing_bits is bounded by largestSupportedIntBits.
}
},
.Bool => {
const opcode: Opcode = if (val.toBool()) .OpConstantTrue else .OpConstantFalse;
try writeInstruction(code, opcode, &[_]Word{ result_type_id, result_id });
@@ -282,8 +316,8 @@ pub const DeclGen = struct {
try writeInstruction(code, .OpConstant, &[_]Word{
result_type_id,
result_id,
@truncate(Word, float_bits),
@truncate(Word, float_bits >> 32),
@truncate(u32, float_bits),
@truncate(u32, float_bits >> @bitSizeOf(u32)),
});
},
128 => unreachable, // Filtered out in the call to getOrGenType.