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Work around divide-by-zero UBSAN errors in intrinsic optimization.

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If the SkSL program contains intrinsics that would divide by zero when
being optimized, the fuzzer would report this as undefined behavior.
Skia insists on IEEE semantics so this isn't a concern for us. We now
use `sk_ieee_double_divide` to work around these fuzzer issues.

Also note that the optimizer will discard results that are not finite,
so these infinite/NaN values are ephemeral anyway--they won't be used
in the final output. The intrinsic in the code will be left
as-is/unoptimized.

Change-Id: I747a434898a15b34716d95f6ca3d29fe4452005d
Bug: oss-fuzz:37850, oss-fuzz:37822, oss-fuzz:37761
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/443399
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
This commit is contained in:
John Stiles 2021-08-30 10:48:32 -04:00
parent 31f763190f
commit a85560a9a3
1 changed files with 8 additions and 3 deletions
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11
src/sksl/ir/SkSLFunctionCall.cpp
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@ -16,6 +16,7 @@
#include "src/sksl/ir/SkSLFunctionCall.h"
#include "src/sksl/ir/SkSLIntLiteral.h"
#include "include/private/SkFloatingPoint.h"
#include "include/sksl/DSLCore.h"
#include "src/core/SkMatrixInvert.h"
@ -404,22 +405,26 @@ double evaluate_log(double a, double, double) { return std::log(a); }
double evaluate_exp2(double a, double, double) { return std::exp2(a); }
double evaluate_log2(double a, double, double) { return std::log2(a); }
double evaluate_sqrt(double a, double, double) { return std::sqrt(a); }
double evaluate_inversesqrt(double a, double, double) { return 1.0 / std::sqrt(a); }
double evaluate_inversesqrt(double a, double, double) {
return sk_ieee_double_divide(1.0, std::sqrt(a));
}
double evaluate_abs(double a, double, double) { return std::abs(a); }
double evaluate_sign(double a, double, double) { return (a > 0) - (a < 0); }
double evaluate_floor(double a, double, double) { return std::floor(a); }
double evaluate_ceil(double a, double, double) { return std::ceil(a); }
double evaluate_fract(double a, double, double) { return a - std::floor(a); }
double evaluate_mod(double a, double b, double) { return a - b * std::floor(a / b); }
double evaluate_min(double a, double b, double) { return (a < b) ? a : b; }
double evaluate_max(double a, double b, double) { return (a > b) ? a : b; }
double evaluate_clamp(double x, double l, double h) { return (x < l) ? l : (x > h) ? h : x; }
double evaluate_saturate(double a, double, double) { return (a < 0) ? 0 : (a > 1) ? 1 : a; }
double evaluate_mix(double x, double y, double a) { return x * (1 - a) + y * a; }
double evaluate_step(double e, double x, double) { return (x < e) ? 0 : 1; }
double evaluate_mod(double a, double b, double) {
return a - b * std::floor(sk_ieee_double_divide(a, b));
}
double evaluate_smoothstep(double edge0, double edge1, double x) {
auto t = (x - edge0) / (edge1 - edge0);
double t = sk_ieee_double_divide(x - edge0, edge1 - edge0);
t = (t < 0) ? 0 : (t > 1) ? 1 : t;
return t * t * (3.0 - 2.0 * t);
}