[Mesa-dev] [PATCH] radv: add a workaround for Monster Hunter World and LLVM 7&8

[Samuel Pitoiset]

The load/store optimizer pass doesn't handle WaW hazards correctly
and this is the root cause of the reflection issue with Monster
Hunter World. AFAIK, it's the only game that are affected by this
issue.

LLVM 9 will be fixed but we need a workaround for older LLVM
versions, see https://reviews.llvm.org/D61313.

Cc: "19.0" "19.1" <mesa-stable at lists.freedesktop.org>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
---
 src/amd/common/ac_llvm_util.c | 7 ++++---
 src/amd/common/ac_llvm_util.h | 1 +
 src/amd/vulkan/radv_debug.h   | 1 +
 src/amd/vulkan/radv_device.c  | 8 ++++++++
 src/amd/vulkan/radv_shader.c  | 2 ++
 5 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/src/amd/common/ac_llvm_util.c b/src/amd/common/ac_llvm_util.c
index 69446863b95..6063411310b 100644
--- a/src/amd/common/ac_llvm_util.c
+++ b/src/amd/common/ac_llvm_util.c
@@ -151,13 +151,14 @@ static LLVMTargetMachineRef ac_create_target_machine(enum radeon_family family,
 	LLVMTargetRef target = ac_get_llvm_target(triple);
 
 	snprintf(features, sizeof(features),
-		 "+DumpCode,-fp32-denormals,+fp64-denormals%s%s%s%s%s",
+		 "+DumpCode,-fp32-denormals,+fp64-denormals%s%s%s%s%s%s",
 		 HAVE_LLVM >= 0x0800 ? "" : ",+vgpr-spilling",
 		 tm_options & AC_TM_SISCHED ? ",+si-scheduler" : "",
 		 tm_options & AC_TM_FORCE_ENABLE_XNACK ? ",+xnack" : "",
 		 tm_options & AC_TM_FORCE_DISABLE_XNACK ? ",-xnack" : "",
-		 tm_options & AC_TM_PROMOTE_ALLOCA_TO_SCRATCH ? ",-promote-alloca" : "");
-	
+		 tm_options & AC_TM_PROMOTE_ALLOCA_TO_SCRATCH ? ",-promote-alloca" : "",
+		 tm_options & AC_TM_NO_LOAD_STORE_OPT ? ",-load-store-opt" : "");
+
 	LLVMTargetMachineRef tm = LLVMCreateTargetMachine(
 	                             target,
 	                             triple,
diff --git a/src/amd/common/ac_llvm_util.h b/src/amd/common/ac_llvm_util.h
index 6d961c06f8a..ca00540da80 100644
--- a/src/amd/common/ac_llvm_util.h
+++ b/src/amd/common/ac_llvm_util.h
@@ -65,6 +65,7 @@ enum ac_target_machine_options {
 	AC_TM_CHECK_IR = (1 << 5),
 	AC_TM_ENABLE_GLOBAL_ISEL = (1 << 6),
 	AC_TM_CREATE_LOW_OPT = (1 << 7),
+	AC_TM_NO_LOAD_STORE_OPT = (1 << 8),
 };
 
 enum ac_float_mode {
diff --git a/src/amd/vulkan/radv_debug.h b/src/amd/vulkan/radv_debug.h
index 17a2f3370c0..652a3b677d2 100644
--- a/src/amd/vulkan/radv_debug.h
+++ b/src/amd/vulkan/radv_debug.h
@@ -51,6 +51,7 @@ enum {
 	RADV_DEBUG_CHECKIR           = 0x200000,
 	RADV_DEBUG_NOTHREADLLVM      = 0x400000,
 	RADV_DEBUG_NOBINNING         = 0x800000,
+	RADV_DEBUG_NO_LOAD_STORE_OPT = 0x1000000,
 };
 
 enum {
diff --git a/src/amd/vulkan/radv_device.c b/src/amd/vulkan/radv_device.c
index 10956ded66f..caf1316096e 100644
--- a/src/amd/vulkan/radv_device.c
+++ b/src/amd/vulkan/radv_device.c
@@ -464,6 +464,7 @@ static const struct debug_control radv_debug_options[] = {
 	{"checkir", RADV_DEBUG_CHECKIR},
 	{"nothreadllvm", RADV_DEBUG_NOTHREADLLVM},
 	{"nobinning", RADV_DEBUG_NOBINNING},
+	{"noloadstoreopt", RADV_DEBUG_NO_LOAD_STORE_OPT},
 	{NULL, 0}
 };
 
@@ -510,6 +511,13 @@ radv_handle_per_app_options(struct radv_instance *instance,
 	} else if (!strcmp(name, "DOOM_VFR")) {
 		/* Work around a Doom VFR game bug */
 		instance->debug_flags |= RADV_DEBUG_NO_DYNAMIC_BOUNDS;
+	} else if (!strcmp(name, "MonsterHunterWorld.exe")) {
+		/* Workaround for a WaW hazard when LLVM moves/merges
+		 * load/store memory operations.
+		 * See https://reviews.llvm.org/D61313
+		 */
+		if (HAVE_LLVM < 0x900)
+			instance->debug_flags |= RADV_DEBUG_NO_LOAD_STORE_OPT;
 	}
 }
 
diff --git a/src/amd/vulkan/radv_shader.c b/src/amd/vulkan/radv_shader.c
index 7568d59056c..b5ee8ac5c51 100644
--- a/src/amd/vulkan/radv_shader.c
+++ b/src/amd/vulkan/radv_shader.c
@@ -649,6 +649,8 @@ shader_variant_create(struct radv_device *device,
 		tm_options |= AC_TM_SISCHED;
 	if (options->check_ir)
 		tm_options |= AC_TM_CHECK_IR;
+	if (device->instance->debug_flags & RADV_DEBUG_NO_LOAD_STORE_OPT)
+		tm_options |= AC_TM_NO_LOAD_STORE_OPT;
 
 	thread_compiler = !(device->instance->debug_flags & RADV_DEBUG_NOTHREADLLVM);
 	radv_init_llvm_once();
-- 
2.21.0