From d34a3b49c3bb00d5bd700b1042a4e3817f8a07e3 Mon Sep 17 00:00:00 2001
From: smolnar <smolnar@mozilla.com>
Date: Sat, 12 Dec 2020 02:51:33 +0200
Subject: [PATCH] Backed out changeset ad64ffa1c7f6 (bug 1678938) for causing
 reftest failures. CLOSED TREE

---
 gfx/tests/crashtests/1678938-1.html  |  9 ---------
 gfx/tests/crashtests/crashtests.list |  2 --
 gfx/wr/swgl/src/gl.cc                | 12 ++----------
 3 files changed, 2 insertions(+), 21 deletions(-)
 delete mode 100644 gfx/tests/crashtests/1678938-1.html

diff --git a/gfx/tests/crashtests/1678938-1.html b/gfx/tests/crashtests/1678938-1.html
deleted file mode 100644
index c2d535c6dc11..000000000000
--- a/gfx/tests/crashtests/1678938-1.html
+++ /dev/null
@@ -1,9 +0,0 @@
-<style>
-:first-of-type {
-  filter: saturate(70%);
-  transform: skew(-224.96198773774648grad) matrix3d(79.00629819492802, -0.0, 43.223526565331326, -294.8479790240964, 269.7, 243.87676190037186, 238.83225166324632, 42.507227157006135, 634943.1, 208.66200905121616, 46.19831959954935, -285.43139932334543, -229.39776691490985, -126.46021751791264, 116.46, 137.77);
-  border-block-end-style: double;
-</style>
-<dl>
-<header>
-</html>
diff --git a/gfx/tests/crashtests/crashtests.list b/gfx/tests/crashtests/crashtests.list
index 9ee62f64324e..be6bbe064b48 100644
--- a/gfx/tests/crashtests/crashtests.list
+++ b/gfx/tests/crashtests/crashtests.list
@@ -198,6 +198,4 @@ load 1650989-very-large-mask.html
 load 1650990.html
 skip-if(!webrender||AddressSanitizer) load 1652750-deep-scene-stack.html
 load 1651882.html
-load 1678938-1.html
 load 1679477-1.html
-
diff --git a/gfx/wr/swgl/src/gl.cc b/gfx/wr/swgl/src/gl.cc
index 21cbe5f0e528..f3dd9996f948 100644
--- a/gfx/wr/swgl/src/gl.cc
+++ b/gfx/wr/swgl/src/gl.cc
@@ -3748,13 +3748,7 @@ static int clip_side(int nump, Point3D* p, Interpolants* interp, Point3D* outP,
         assert(numClip < nump + 2);
         float prevDist = prevCoord - prevSide * prev.w;
         float curDist = curCoord - prevSide * cur.w;
-        // It may happen that after we interpolate by the weight k that due to
-        // floating point rounding we've underestimated the value necessary to
-        // push it over the clipping boundary. Just in case, nudge the mantissa
-        // by a single increment so that we essentially round it up and move it
-        // further inside the clipping boundary. We use nextafter to do this in
-        // a portable fashion.
-        float k = nextafterf(prevDist / (prevDist - curDist), 1.0f);
+        float k = prevDist / (prevDist - curDist);
         outP[numClip] = prev + (cur - prev) * k;
         outInterp[numClip] = prevInterp + (curInterp - prevInterp) * k;
         numClip++;
@@ -3766,9 +3760,7 @@ static int clip_side(int nump, Point3D* p, Interpolants* interp, Point3D* outP,
         assert(numClip < nump + 2);
         float prevDist = prevCoord - curSide * prev.w;
         float curDist = curCoord - curSide * cur.w;
-        // Calculate interpolation weight k and the nudge it inside clipping
-        // boundary with nextafter.
-        float k = nextafterf(prevDist / (prevDist - curDist), 1.0f);
+        float k = prevDist / (prevDist - curDist);
         outP[numClip] = prev + (cur - prev) * k;
         outInterp[numClip] = prevInterp + (curInterp - prevInterp) * k;
         numClip++;