src/compiler/translator/tree_util/SpecializationConstant.cpp


Log

Author Commit Date CI Message
Shahbaz Youssefi 6f80f0f0 2022-08-06T02:29:19 Translator: Clean up the compile flag passing interface Historically, compile flags were sent to the translator as a bitmask. Recently, we were getting close to running out of bits. Additionally, direct-to-metal work had started to introduce constants to be passed to the translator, which were misplaced in ShBuiltInResources and Caps. Recent work on Pixel Local Storage adds even more constants, aggravating the situation. In this change, the interface to passing compile flags is reworked. A struct is passed (instead of a bitmask) that has one bit for each flag. This can be indefinitely extended. Additionally, the constants needed by metal and PLS are also placed in this struct. In turn, the backends can set these options directly, and don't have to hack them into Caps to further get hacked into ShBuiltInResources. Bug: angleproject:7559 Change-Id: If93f1e1b8818ad3a0ac708ab04ab93b4b397d114 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3812562 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Amirali Abdolrashidi <abdolrashidi@google.com> Commit-Queue: Amirali Abdolrashidi <abdolrashidi@google.com> Auto-Submit: Shahbaz Youssefi <syoussefi@chromium.org>
Amirali Abdolrashidi 3b988fef 2022-06-01T10:54:03 Vulkan: Remove enableLineRasterEmulation * Removed the Bresenham line raster emulation specialization constant, along with related variables and functions. Bug: angleproject:7366 Change-Id: If17c8ce9b459ad801bae8e887e5674bd9a3ff2bf Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3680860 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Charlie Lao <cclao@google.com>
Shahbaz Youssefi 23f213d1 2022-05-26T23:43:44 Vulkan: Make drawable size uniform As a specialization constant, it's impossible to predict the value the drawable size may take, which in turn makes it impossible to warm up the Vulkan pipeline cache at link time. Bug: angleproject:7366 Change-Id: Ia3d1860a4fcb8e3078fdcb8d02a2e0cd173ea028 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3671976 Reviewed-by: Charlie Lao <cclao@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Shahbaz Youssefi 98c2e169 2022-05-20T16:17:49 Vulkan: Reduce pre-rotation spec const to bool The specialization constant now only dictates whether x and y should be swapped. The complete 8 possible states of rotation and y-flip are achieved by using this swap in combination with a driver uniform for x and y flip. Swapping is still a specialization constant to avoid degrading performance of dFdx/dFdy which otherwise would need both to be evaluated instead of one. On platforms which don't support pre-rotation, the specialization constant will never change and driver uniforms entirely govern y-flip. On platforms that do support pre-rotation, only two variations of the pipeline are needed. Bug: angleproject:7366 Change-Id: I73f84e89fa9349d2098fa5b21573aee57d93a30c Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3663151 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Lingfeng Yang <lfy@google.com> Reviewed-by: Charlie Lao <cclao@google.com>
Shahbaz Youssefi 665ddccd 2021-12-09T23:06:39 Vulkan: Emulate dithering Dithering in OpenGL is vaguely defined, to the extent that no dithering is also a valid dithering algorithm. Dithering is enabled by default, but emulating it has a non-negligible cost. Similarly to some other GLES drivers, ANGLE enables dithering only on low-bit formats where visual banding is particularly common; namely RGBA4444, RGBA5551 and RGB565. Dithering is emulated in the fragment shader and is controlled by a spec constant. Every 2 bits of the spec constant correspond to one attachment, with the value indicating: - 00: No dithering - 01: Dither for RGBA4444 - 10: Dither for RGBA5551 - 11: Dither for RGB565 The translator appends code to the shader that, based on the format specified by the specialization constant, adds dithering to each color attachment output. A 2x2 Bayer matrix is used for dithering, indexed by gl_FragCoord.xy % 2. Bug: angleproject:6755 Change-Id: Ib45da5938e299b6626bff921119d63e7357dd353 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3374261 Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Shahbaz Youssefi 095d7c0a 2022-01-06T01:20:53 Translator: Clean up spec const / driver uniform types Bug: angleproject:6755 Change-Id: I8fb1557a5e29fcc28d5cb2f3aaa2c4a14b72583d Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3369125 Reviewed-by: Tim Van Patten <timvp@google.com> Commit-Queue: Tim Van Patten <timvp@google.com>
Lingfeng Yang 9ba5dcf6 2021-10-07T06:56:14 Vulkan: Fix inconsistency in half render area width/height The half render area rotation matrix should be removed. DrawableArea is constant over rotations. The frag coord rotation matrix is still needed because the frag coord generated by GPU is still rotated. Test: DISPLAY=:0 out/Debug/angle_deqp_gles3_rotate90_tests Using test config with: linux nvidia debug vulkan prerotation prerotation270 Test: Cuttlefish SwANGLE ./cts-tradefed run cts -m CtsDeqpTestCases -t dEQP-GLES3.functional.shaders.builtin_variable.fragcoord_xyz Bug: angleproject:6504 Change-Id: I37a6308fdb7586200b19a6138affc78c2c329a96 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3212427 Commit-Queue: Lingfeng Yang <lfy@google.com> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Charlie Lao <cclao@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>
Shahbaz Youssefi 32d6e806 2021-09-24T23:50:54 Vulkan: Fix rotation of interpolateAtOffset interpolateAtOffset's offset was multiplied by flipXY*rotationMatrix, which is a vector. This was unable to actually apply rotation to the offset. The multiplier is changed to a matrix. Can be tested by running interpolate_at_offset*default_framebuffer tests in deqp gles3.1 together with pre-rotation: ./angle_deqp_gles31_tests --deqp-case=dEQP.GLES31/functional_shaders_multisample_interpolation_interpolate_at_offset_no_qualifiers_default_framebuffer --emulated-pre-rotation=90 Bug: angleproject:5843 Change-Id: I9727371375e999f07463b69153df3fd8b28c2a71 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3183108 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Ian Elliott <ianelliott@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Shahbaz Youssefi 800e82c6 2021-08-23T11:05:23 Translator: Validate precisions When declaring a variable, a struct field, function parameter etc, there's a precision necessarily applied to the entity being declared. AST Validation is added to enforce this. Intermediate nodes derive their precision from these entities automatically. Consistency of intermediate nodes is not validated. This is because AST transformations replace a node with a transformed one, and that may not have the same precision. Take the following code: mediump float x = ...; mediump float y = ...; ... x + y ... and assume is transformed as such: highp float driver_uniform; ... (x * driver_uniform) + y ... The addition was originally done in mediump, but would seemingly need to be done in highp after transformation. There are a number of options here: - Make sure that when nodes are replaced, the precision is unaffected. This can be intrusive, requiring temp variables. - Bubble up the new precision - Accept the discrepancy ANGLE opts for the last option, which actually respects the original shader's intended precision for operations, even if some transformation needs to temporarily evaluate an expression at a higher precision. Bug: angleproject:4889 Bug: angleproject:6132 Change-Id: Ibcde3a230de159157783b1c6d5ef1cd63ceb4d8f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3114027 Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Shahbaz Youssefi 210773db 2021-08-05T10:41:59 Translator: Be more explicit about precisions GLSL ES requires that every symbol (variable, block member, function parameter and return value) is appropriately qualified with a precision, either individually or through the global precision specifier. Some tree transformations however produced symbols with EbpUndefined precision. In text GLSL output, these would produce unqualified symbols which was often incorrect. In this change, the transformations are made to produce explicit / more consistent precisions. The validation (that caught these issues) is not included in this change as there are still a few corner cases left to address. Bug: angleproject:4889 Bug: angleproject:6132 Change-Id: Icca8a0a5476f8646226e7243aa8f501f44acc164 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3075127 Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Shahbaz Youssefi e3e7447a 2021-07-08T22:22:19 Vulkan: Fix flipXY for 180 degree prerotation and spec consts The multiplier used for flipXY in this configuration was incorrect. Bug: angleproject:5348 Bug: angleproject:5349 Bug: angleproject:5350 Change-Id: I0b3771f6a9da6ab2af02ed5ee5fe7b49d0415410 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3016768 Reviewed-by: Ian Elliott <ianelliott@google.com> Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Shahbaz Youssefi 7d023dac 2021-06-10T00:13:41 Vulkan: SPIR-V Gen: Basic support for fragment shaders Fragment shader built-ins are implemented in this change and direct SPIR-V generation for fragment shaders is enabled. Bug: angleproject:4889 Change-Id: I6f92a5585f242122a81c97a9b1aa2763009161a0 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2951625 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>
Shahbaz Youssefi 31641b8e 2021-06-05T02:17:47 Declare specialization constants in the AST A new qualifier (EvqSpecConst) is added so that specialization constants can be declared in tree. This enables TVariable references to specialization constants to be validated, which were in fact invalid as every reference declared a new variable. That is fixed. Bug: angleproject:4889 Change-Id: I1711e41cbc5a1260843d2d004d3568bdae11e963 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2941451 Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Kyle Piddington d7aa0130 2021-04-26T16:56:15 Upstream Apple's direct-to-Metal backend: compile translator. This change is meant to merge the translator changes from Apple's direct-to-Metal backend. Taken from Kyle Piddington's CL: https://chromium-review.googlesource.com/c/angle/angle/+/2857366/ The goal of this CL is to merge the translator code in a state that compiles, but not to switch the Metal backend over to use this translator backend yet. Bug: angleproject:5505 Change-Id: I68a6354604498cd5fd1eb96c13fc56f3b38f2bd0 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2897536 Reviewed-by: Jonah Ryan-Davis <jonahr@google.com> Commit-Queue: Jonah Ryan-Davis <jonahr@google.com>
Shahbaz Youssefi 58eabfd7 2021-04-08T23:57:04 Translator: Validate consistent variable references Some transformations change variable declarations. This validation ensures that all references to said variables are appropriately replaced as well. Bug: angleproject:2733 Change-Id: I6c2873968eeed4cba66e70069f84eb69a1f77074 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2818140 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com>
Shahbaz Youssefi b1deba2f 2021-01-28T16:06:51 Vulkan: Don't emit spec const declaration in compute shaders Bug: angleproject:5070 Change-Id: I74becfeac88b4a8ff66dd36670792082d0b941cd Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2658882 Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Shahbaz Youssefi f0286e63 2021-01-19T12:38:46 Translator: Stop allocating TIntermSequence The functions that take a TIntermSequence always copy out / Swap the contents away. This change makes all TIntermSequences live on the stack instead of being newed. Bug: angleproject:5535 Change-Id: I942f1c5e57b00199d5308183f71bd9e18b0608bd Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2636679 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Shahbaz Youssefi bd2954a9 2021-01-16T11:33:12 Reland "Cleanup translator option checks" This reverts commit 9173e01730923823846348e513bb8cbe7eddbbe5. Reason for revert: This was in a chain of reverts, but is unrelated to the issue. Original change's description: > Revert "Cleanup translator option checks" > > This reverts commit 9710c4e473c88a38f11eb10c600717181d6e24df. > > Reason for revert: > Earlier CL breaks pre-rotation: > https://chromium-review.googlesource.com/c/angle/angle/+/2598584 > > Original change's description: > > Cleanup translator option checks > > > > Use comparison with 0 for explicit conversion to bool. > > > > Bug: angleproject:3606 > > Change-Id: Ie0a76d7df829227c1376894535813b54e13491b4 > > Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2631689 > > Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> > > Reviewed-by: Charlie Lao <cclao@google.com> > > Reviewed-by: Jamie Madill <jmadill@chromium.org> > > TBR=syoussefi@chromium.org,jmadill@chromium.org,cclao@google.com > > Change-Id: Ib597a62f3c7078d28f7f5b79d1cc9f8d9e469c31 > No-Presubmit: true > No-Tree-Checks: true > No-Try: true > Bug: angleproject:3606 > Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2634047 > Reviewed-by: Tim Van Patten <timvp@google.com> > Commit-Queue: Tim Van Patten <timvp@google.com> TBR=timvp@google.com,syoussefi@chromium.org,jmadill@chromium.org,cclao@google.com Bug: angleproject:3606 Change-Id: I10ecca63a3db6dbc3ddedf5bb7e5319a82a80a30 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2633712 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Shahbaz Youssefi dfd9bdfd 2021-01-16T11:32:30 Reland "Vulkan: Generate gl_Position pre-rotation in SPIR-V" This reverts commit 3d39b7c5eab88c420d982155ffbb6181c678ceea. Reason for revert: Fixed interaction with the `forceDriverUniformOverSpecConst` workaround. Original change's description: > Revert "Vulkan: Generate gl_Position pre-rotation in SPIR-V" > > This reverts commit 0f86b196ffaffeeee3460e3188f20a7ac120796d. > > Reason for revert: > Breaks pre-rotation for all apps, so they are displayed in portrait instead of landscape. > > Original change's description: > > Vulkan: Generate gl_Position pre-rotation in SPIR-V > > > > Instead of having the translator output pre-rotation code in the vertex > > stage based on a specialization constant, this change makes the SPIR-V > > transformer perform pre-rotation of gl_Position on the last geometry > > stage. > > > > An alternative solution would be to generate pre-rotation code in the > > translator in every geometry stage, each controlled by a separate > > specialization constant. This change avoids unnecessary modifications > > to earlier stages. The generated shaders are also smaller, as they > > don't contain a mat2[8] pre-rotation constant matrix. The SPIR-V > > transformer knows the pre-rotation at transformation time, so it can > > simply use swizzles to achieve the same results. > > > > This also ties in with upcoming changes which move gl_Position.z > > correction to the last geometry shader stage, which is trivially done > > piggy-backing on the infrastructure in this change. > > > > Bug: angleproject:5478 > > Change-Id: I9d5d9d19f3ccda665f5504368ce5ddfa5f383faf > > Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2598584 > > Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> > > Reviewed-by: Charlie Lao <cclao@google.com> > > Reviewed-by: Jamie Madill <jmadill@chromium.org> > > TBR=syoussefi@chromium.org,jmadill@chromium.org,cclao@google.com > > Change-Id: I81f237fa6b10c7d59831363bee8999e7ad2f09be > No-Presubmit: true > No-Tree-Checks: true > No-Try: true > Bug: angleproject:5478 > Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2633694 > Reviewed-by: Tim Van Patten <timvp@google.com> > Commit-Queue: Tim Van Patten <timvp@google.com> TBR=timvp@google.com,syoussefi@chromium.org,jmadill@chromium.org,cclao@google.com Bug: angleproject:5478 Change-Id: I7c5eaeef03d9520abd36a1c4a766b6abbf4fdb45 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2633709 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Tim Van Patten 3d39b7c5 2021-01-16T00:15:14 Revert "Vulkan: Generate gl_Position pre-rotation in SPIR-V" This reverts commit 0f86b196ffaffeeee3460e3188f20a7ac120796d. Reason for revert: Breaks pre-rotation for all apps, so they are displayed in portrait instead of landscape. Original change's description: > Vulkan: Generate gl_Position pre-rotation in SPIR-V > > Instead of having the translator output pre-rotation code in the vertex > stage based on a specialization constant, this change makes the SPIR-V > transformer perform pre-rotation of gl_Position on the last geometry > stage. > > An alternative solution would be to generate pre-rotation code in the > translator in every geometry stage, each controlled by a separate > specialization constant. This change avoids unnecessary modifications > to earlier stages. The generated shaders are also smaller, as they > don't contain a mat2[8] pre-rotation constant matrix. The SPIR-V > transformer knows the pre-rotation at transformation time, so it can > simply use swizzles to achieve the same results. > > This also ties in with upcoming changes which move gl_Position.z > correction to the last geometry shader stage, which is trivially done > piggy-backing on the infrastructure in this change. > > Bug: angleproject:5478 > Change-Id: I9d5d9d19f3ccda665f5504368ce5ddfa5f383faf > Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2598584 > Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> > Reviewed-by: Charlie Lao <cclao@google.com> > Reviewed-by: Jamie Madill <jmadill@chromium.org> TBR=syoussefi@chromium.org,jmadill@chromium.org,cclao@google.com Change-Id: I81f237fa6b10c7d59831363bee8999e7ad2f09be No-Presubmit: true No-Tree-Checks: true No-Try: true Bug: angleproject:5478 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2633694 Reviewed-by: Tim Van Patten <timvp@google.com> Commit-Queue: Tim Van Patten <timvp@google.com>
Tim Van Patten 9173e017 2021-01-16T00:10:34 Revert "Cleanup translator option checks" This reverts commit 9710c4e473c88a38f11eb10c600717181d6e24df. Reason for revert: Earlier CL breaks pre-rotation: https://chromium-review.googlesource.com/c/angle/angle/+/2598584 Original change's description: > Cleanup translator option checks > > Use comparison with 0 for explicit conversion to bool. > > Bug: angleproject:3606 > Change-Id: Ie0a76d7df829227c1376894535813b54e13491b4 > Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2631689 > Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> > Reviewed-by: Charlie Lao <cclao@google.com> > Reviewed-by: Jamie Madill <jmadill@chromium.org> TBR=syoussefi@chromium.org,jmadill@chromium.org,cclao@google.com Change-Id: Ib597a62f3c7078d28f7f5b79d1cc9f8d9e469c31 No-Presubmit: true No-Tree-Checks: true No-Try: true Bug: angleproject:3606 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2634047 Reviewed-by: Tim Van Patten <timvp@google.com> Commit-Queue: Tim Van Patten <timvp@google.com>
Shahbaz Youssefi 9710c4e4 2021-01-14T22:41:48 Cleanup translator option checks Use comparison with 0 for explicit conversion to bool. Bug: angleproject:3606 Change-Id: Ie0a76d7df829227c1376894535813b54e13491b4 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2631689 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Charlie Lao <cclao@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>
Shahbaz Youssefi 0f86b196 2020-12-21T22:54:05 Vulkan: Generate gl_Position pre-rotation in SPIR-V Instead of having the translator output pre-rotation code in the vertex stage based on a specialization constant, this change makes the SPIR-V transformer perform pre-rotation of gl_Position on the last geometry stage. An alternative solution would be to generate pre-rotation code in the translator in every geometry stage, each controlled by a separate specialization constant. This change avoids unnecessary modifications to earlier stages. The generated shaders are also smaller, as they don't contain a mat2[8] pre-rotation constant matrix. The SPIR-V transformer knows the pre-rotation at transformation time, so it can simply use swizzles to achieve the same results. This also ties in with upcoming changes which move gl_Position.z correction to the last geometry shader stage, which is trivially done piggy-backing on the infrastructure in this change. Bug: angleproject:5478 Change-Id: I9d5d9d19f3ccda665f5504368ce5ddfa5f383faf Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2598584 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Charlie Lao <cclao@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>
Charlie Lao c75473c2 2020-11-23T14:26:32 Vulkan: Generalize FlipRotationSpecConst to SpecializationConstant Specialization constant are used not just for flip/rotation. It also used for other things. This CL merges all specialization constant usage (lineRasterEmulation, flip, rotation, halfRenderArea) into one class and rename FlipRotationSpecConst to SpecConst. Bug: b/173800146 Change-Id: I8dc3354b6caedbb183cec29855fc1c301ec8872a Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2555812 Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>