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tint: Fix C++ UB when shifting abstract 0 left by >= 64 

In WGSL, we can shift left abstracts by >= 64, as long as the result is
representable in the data type we choose for it. When shifting 0, we can
shift by any positive u32 value (result is always 0), but in C++, it's
UB to shift by more than the bit width of the data type, so we need to
handle this. This bug was caught by ClusterFuzz.

Bug: chromium:1372963
Change-Id: I638ca190b93538908ca6472f3735627ea8531c5a
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/106266
Reviewed-by: David Neto <dneto@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
This commit is contained in:
Antonio Maiorano 2022-10-18 20:17:55 +00:00 committed by Dawn LUCI CQ
parent e4d608a837
commit b6e1bc7d5d
9 changed files with 140 additions and 10 deletions
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4
src/tint/resolver/const_eval.cc
View File

@ -1474,6 +1474,10 @@ ConstEval::Result ConstEval::OpShiftLeft(const sem::Type* ty,
AddError(OverflowErrorMessage(e1, "<<", e2), source);
return nullptr;
}
// It's UB in C++ to shift by greater or equal to the bit width (even if the lhs
// is 0), so we make sure to avoid this by setting the shift value to 0.
e2 = 0;
}
} else {
if (static_cast<size_t>(e2) >= bit_width) {

47
src/tint/resolver/const_eval_binary_op_test.cc
View File

@ -598,7 +598,7 @@ std::vector<Case> ShiftLeftCases() {
// Shift type is u32 for non-abstract
using ST = std::conditional_t<IsAbstract<T>, T, u32>;
using B = BitValues<T>;
return {
auto r = std::vector<Case>{
C(T{0b1010}, ST{0}, T{0b0000'0000'1010}), //
C(T{0b1010}, ST{1}, T{0b0000'0001'0100}), //
C(T{0b1010}, ST{2}, T{0b0000'0010'1000}), //
@ -626,6 +626,25 @@ std::vector<Case> ShiftLeftCases() {
Vec(ST{6}, ST{7}, ST{8}), //
Vec(T{0b0010'1000'0000}, T{0b0101'0000'0000}, T{0b1010'0000'0000})), //
};
// Only abstract 0 can be shifted left as much as we like. For concrete 0 (and any number), it
// cannot be shifted equal or more than the number of bits of the lhs (see
// ResolverConstEvalShiftLeftConcreteGeqBitWidthError)
ConcatIntoIf<IsAbstract<T>>( //
r, std::vector<Case>{
C(T{0}, ST{64}, T{0}),
C(T{0}, ST{65}, T{0}),
C(T{0}, ST{65}, T{0}),
C(T{0}, ST{10000}, T{0}),
C(T{0}, T::Highest(), T{0}),
C(Negate(T{0}), ST{64}, Negate(T{0})),
C(Negate(T{0}), ST{65}, Negate(T{0})),
C(Negate(T{0}), ST{65}, Negate(T{0})),
C(Negate(T{0}), ST{10000}, Negate(T{0})),
C(Negate(T{0}), T::Highest(), Negate(T{0})),
});
return r;
}
INSTANTIATE_TEST_SUITE_P(ShiftLeft,
ResolverConstEvalBinaryOpTest,
@ -851,14 +870,36 @@ TEST_P(ResolverConstEvalShiftLeftConcreteGeqBitWidthError, Test) {
INSTANTIATE_TEST_SUITE_P(Test,
ResolverConstEvalShiftLeftConcreteGeqBitWidthError,
testing::Values( //
std::make_tuple(Val(0_u), Val(32_u)), //
std::make_tuple(Val(0_u), Val(33_u)), //
std::make_tuple(Val(0_u), Val(34_u)), //
std::make_tuple(Val(0_u), Val(10000_u)), //
std::make_tuple(Val(0_u), Val(u32::Highest())), //
std::make_tuple(Val(0_i), Val(32_u)), //
std::make_tuple(Val(0_i), Val(33_u)), //
std::make_tuple(Val(0_i), Val(34_u)), //
std::make_tuple(Val(0_i), Val(10000_u)), //
std::make_tuple(Val(0_i), Val(u32::Highest())), //
std::make_tuple(Val(Negate(0_u)), Val(32_u)), //
std::make_tuple(Val(Negate(0_u)), Val(33_u)), //
std::make_tuple(Val(Negate(0_u)), Val(34_u)), //
std::make_tuple(Val(Negate(0_u)), Val(10000_u)), //
std::make_tuple(Val(Negate(0_u)), Val(u32::Highest())), //
std::make_tuple(Val(Negate(0_i)), Val(32_u)), //
std::make_tuple(Val(Negate(0_i)), Val(33_u)), //
std::make_tuple(Val(Negate(0_i)), Val(34_u)), //
std::make_tuple(Val(Negate(0_i)), Val(10000_u)), //
std::make_tuple(Val(Negate(0_i)), Val(u32::Highest())), //
std::make_tuple(Val(1_i), Val(32_u)), //
std::make_tuple(Val(1_i), Val(33_u)), //
std::make_tuple(Val(1_i), Val(34_u)), //
std::make_tuple(Val(1_i), Val(99999999_u)), //
std::make_tuple(Val(1_i), Val(10000_u)), //
std::make_tuple(Val(1_i), Val(u32::Highest())), //
std::make_tuple(Val(1_u), Val(32_u)), //
std::make_tuple(Val(1_u), Val(33_u)), //
std::make_tuple(Val(1_u), Val(34_u)), //
std::make_tuple(Val(1_u), Val(99999999_u)) //
std::make_tuple(Val(1_u), Val(10000_u)), //
std::make_tuple(Val(1_u), Val(u32::Highest())) //
));
// AInt left shift results in sign change error

8
test/tint/bug/chromium/1372963.wgsl Normal file
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@ -0,0 +1,8 @@
fn g() -> vec4<i32> {
return vec4(-0) << vec4(2147483649);
}
@fragment
fn main() {
g();
}

8
test/tint/bug/chromium/1372963.wgsl.expected.dxc.hlsl Normal file
View File

@ -0,0 +1,8 @@
int4 g() {
return (0).xxxx;
}
void main() {
g();
return;
}

8
test/tint/bug/chromium/1372963.wgsl.expected.fxc.hlsl Normal file
View File

@ -0,0 +1,8 @@
int4 g() {
return (0).xxxx;
}
void main() {
g();
return;
}

15
test/tint/bug/chromium/1372963.wgsl.expected.glsl Normal file
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@ -0,0 +1,15 @@
#version 310 es
precision mediump float;
ivec4 g() {
return ivec4(0);
}
void tint_symbol() {
g();
}
void main() {
tint_symbol();
return;
}

12
test/tint/bug/chromium/1372963.wgsl.expected.msl Normal file
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@ -0,0 +1,12 @@
#include <metal_stdlib>
using namespace metal;
int4 g() {
return int4(0);
}
fragment void tint_symbol() {
g();
return;
}

26
test/tint/bug/chromium/1372963.wgsl.expected.spvasm Normal file
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@ -0,0 +1,26 @@
; SPIR-V
; Version: 1.3
; Generator: Google Tint Compiler; 0
; Bound: 12
; Schema: 0
OpCapability Shader
OpMemoryModel Logical GLSL450
OpEntryPoint Fragment %main "main"
OpExecutionMode %main OriginUpperLeft
OpName %g "g"
OpName %main "main"
%int = OpTypeInt 32 1
%v4int = OpTypeVector %int 4
%1 = OpTypeFunction %v4int
%6 = OpConstantNull %v4int
%void = OpTypeVoid
%7 = OpTypeFunction %void
%g = OpFunction %v4int None %1
%5 = OpLabel
OpReturnValue %6
OpFunctionEnd
%main = OpFunction %void None %7
%10 = OpLabel
%11 = OpFunctionCall %v4int %g
OpReturn
OpFunctionEnd

8
test/tint/bug/chromium/1372963.wgsl.expected.wgsl Normal file
View File

@ -0,0 +1,8 @@
fn g() -> vec4<i32> {
return (vec4(0) << vec4(2147483649));
}
@fragment
fn main() {
g();
}