Mesa (master): Revert "i915: Always enable GL 2.0 support."

[Matt Turner]

Module: Mesa
Branch: master
Commit: a1891da7c865c80d95c450abfc0d2bc49db5f678
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=a1891da7c865c80d95c450abfc0d2bc49db5f678

Author: Matt Turner <mattst88 at gmail.com>
Date:   Sun Jan 29 18:20:10 2017 -0800

Revert "i915: Always enable GL 2.0 support."

This partially reverts commit 97217a40f97cdeae0304798b607f704deb0c3558.
It leaves ES 2.0 support in place per Ian's suggestion, because ES 2.0
is designed to work on hardware like i915.

Chrome only uses the GPU if you have GL >= 2.0, and using i915 (and
prog_execute) actually hurt performance compared with the software
paths.

---

 src/mesa/drivers/dri/i915/intel_extensions.c |  8 ++++++--
 src/mesa/drivers/dri/i915/intel_screen.c     | 21 +++++++++++++++++++--
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/src/mesa/drivers/dri/i915/intel_extensions.c b/src/mesa/drivers/dri/i915/intel_extensions.c
index ab7820f..4f2c6fa 100644
--- a/src/mesa/drivers/dri/i915/intel_extensions.c
+++ b/src/mesa/drivers/dri/i915/intel_extensions.c
@@ -92,8 +92,12 @@ intelInitExtensions(struct gl_context *ctx)
       ctx->Extensions.ATI_separate_stencil = true;
       ctx->Extensions.ATI_texture_env_combine3 = true;
       ctx->Extensions.NV_texture_env_combine4 = true;
-      ctx->Extensions.ARB_fragment_shader = true;
-      ctx->Extensions.ARB_occlusion_query = true;
+
+      if (driQueryOptionb(&intel->optionCache, "fragment_shader"))
+         ctx->Extensions.ARB_fragment_shader = true;
+
+      if (driQueryOptionb(&intel->optionCache, "stub_occlusion_query"))
+         ctx->Extensions.ARB_occlusion_query = true;
    }
 
    if (intel->ctx.Mesa_DXTn
diff --git a/src/mesa/drivers/dri/i915/intel_screen.c b/src/mesa/drivers/dri/i915/intel_screen.c
index 5c7c06a..fe86179 100644
--- a/src/mesa/drivers/dri/i915/intel_screen.c
+++ b/src/mesa/drivers/dri/i915/intel_screen.c
@@ -62,6 +62,10 @@ DRI_CONF_BEGIN
 	 DRI_CONF_DESC(en, "Enable early Z in classic mode (unstable, 945-only).")
       DRI_CONF_OPT_END
 
+      DRI_CONF_OPT_BEGIN_B(fragment_shader, "true")
+	 DRI_CONF_DESC(en, "Enable limited ARB_fragment_shader support on 915/945.")
+      DRI_CONF_OPT_END
+
    DRI_CONF_SECTION_END
    DRI_CONF_SECTION_QUALITY
       DRI_CONF_FORCE_S3TC_ENABLE("false")
@@ -75,6 +79,10 @@ DRI_CONF_BEGIN
       DRI_CONF_DISABLE_GLSL_LINE_CONTINUATIONS("false")
       DRI_CONF_DISABLE_BLEND_FUNC_EXTENDED("false")
 
+      DRI_CONF_OPT_BEGIN_B(stub_occlusion_query, "false")
+	 DRI_CONF_DESC(en, "Enable stub ARB_occlusion_query support on 915/945.")
+      DRI_CONF_OPT_END
+
       DRI_CONF_OPT_BEGIN_B(shader_precompile, "true")
 	 DRI_CONF_DESC(en, "Perform code generation at shader link time.")
       DRI_CONF_OPT_END
@@ -1125,12 +1133,21 @@ set_max_gl_versions(struct intel_screen *screen)
    __DRIscreen *psp = screen->driScrnPriv;
 
    switch (screen->gen) {
-   case 3:
+   case 3: {
+      bool has_fragment_shader = driQueryOptionb(&screen->optionCache, "fragment_shader");
+      bool has_occlusion_query = driQueryOptionb(&screen->optionCache, "stub_occlusion_query");
+
       psp->max_gl_core_version = 0;
       psp->max_gl_es1_version = 11;
-      psp->max_gl_compat_version = 21;
       psp->max_gl_es2_version = 20;
+
+      if (has_fragment_shader && has_occlusion_query) {
+         psp->max_gl_compat_version = 21;
+      } else {
+         psp->max_gl_compat_version = 14;
+      }
       break;
+   }
    case 2:
       psp->max_gl_core_version = 0;
       psp->max_gl_compat_version = 13;