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swiftshader
Commit a2749f39 by Ben Clayton
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SpirvShader: Fix for integer overflow in SDiv and SMod.

See b/128614198 for context. Tests: dEQP-VK.glsl.operator.binary_operator.div.*ivec* Tests: dEQP-VK.glsl.operator.binary_operator.mod.*ivec* Bug: b/128614198 Change-Id: I3c517a18ce003466b1ba382f1896b356e543f5d5 Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/27248 Presubmit-Ready: Ben Clayton <bclayton@google.com> Reviewed-by: 's avatarNicolas Capens <nicolascapens@google.com> Reviewed-by: 's avatarChris Forbes <chrisforbes@google.com> Kokoro-Presubmit: kokoro <noreply+kokoro@google.com> Tested-by: 's avatarBen Clayton <bclayton@google.com>
parent af973b67
Showing with 10 additions and 6 deletions
src/Pipeline/SpirvShader.cpp
...@@ -1538,8 +1538,11 @@ namespace sw ...@@ -1538,8 +1538,11 @@ namespace sw
break; break;
case spv::OpSDiv: case spv::OpSDiv:
{ {
auto zeroMask = CmpEQ(rhs.Int(i), SIMD::Int(0)); SIMD::Int a = lhs.Int(i);
dst.emplace(i, lhs.Int(i) / (rhs.Int(i) | zeroMask)); SIMD::Int b = rhs.Int(i);
b = b | CmpEQ(b, SIMD::Int(0)); // prevent divide-by-zero
a = a | (CmpEQ(a, SIMD::Int(0x80000000)) & CmpEQ(b, SIMD::Int(-1))); // prevent integer overflow
dst.emplace(i, a / b);
break; break;
} }
case spv::OpUDiv: case spv::OpUDiv:
...@@ -1550,10 +1553,11 @@ namespace sw ...@@ -1550,10 +1553,11 @@ namespace sw
} }
case spv::OpSMod: case spv::OpSMod:
{ {
auto a = lhs.Int(i); SIMD::Int a = lhs.Int(i);
auto b = rhs.Int(i); SIMD::Int b = rhs.Int(i);
auto zeroMask = CmpEQ(b, SIMD::Int(0)); b = b | CmpEQ(b, SIMD::Int(0)); // prevent divide-by-zero
auto mod = a % (b | zeroMask); a = a | (CmpEQ(a, SIMD::Int(0x80000000)) & CmpEQ(b, SIMD::Int(-1))); // prevent integer overflow
auto mod = a % b;
// If a and b have opposite signs, the remainder operation takes // If a and b have opposite signs, the remainder operation takes
// the sign from a but OpSMod is supposed to take the sign of b. // the sign from a but OpSMod is supposed to take the sign of b.
// Adding b will ensure that the result has the correct sign and // Adding b will ensure that the result has the correct sign and
......
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