[Mesa-dev] [PATCH 05/10] intel/fs: Respect CHV/BXT regioning restrictions in copy propagation pass.

[Francisco Jerez]

Currently the visitor attempts to enforce the regioning restrictions
that apply to double-precision instructions on CHV/BXT at NIR-to-i965
translation time.  It is possible though for the copy propagation pass
to violate this restriction if a strided move is propagated into one
of the affected instructions.  I've only reproduced this issue on a
future platform but it could affect CHV/BXT too under the right
conditions.

Cc: mesa-stable at lists.freedesktop.org
---
 .../compiler/brw_fs_copy_propagation.cpp      | 10 +++++++
 src/intel/compiler/brw_ir_fs.h                | 28 +++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/src/intel/compiler/brw_fs_copy_propagation.cpp b/src/intel/compiler/brw_fs_copy_propagation.cpp
index a8ec1c34630..c23ce1ef426 100644
--- a/src/intel/compiler/brw_fs_copy_propagation.cpp
+++ b/src/intel/compiler/brw_fs_copy_propagation.cpp
@@ -315,6 +315,16 @@ can_take_stride(fs_inst *inst, unsigned arg, unsigned stride,
    if (stride > 4)
       return false;
 
+   /* Bail if the channels of the source need to be aligned to the byte offset
+    * of the corresponding channel of the destination, and the provided stride
+    * would break this restriction.
+    */
+   if (has_dst_aligned_region_restriction(devinfo, inst) &&
+       !(type_sz(inst->src[arg].type) * stride ==
+           type_sz(inst->dst.type) * inst->dst.stride ||
+         stride == 0))
+      return false;
+
    /* 3-source instructions can only be Align16, which restricts what strides
     * they can take. They can only take a stride of 1 (the usual case), or 0
     * with a special "repctrl" bit. But the repctrl bit doesn't work for
diff --git a/src/intel/compiler/brw_ir_fs.h b/src/intel/compiler/brw_ir_fs.h
index 07e7224e0f8..95b069a2e02 100644
--- a/src/intel/compiler/brw_ir_fs.h
+++ b/src/intel/compiler/brw_ir_fs.h
@@ -486,4 +486,32 @@ get_exec_type_size(const fs_inst *inst)
    return type_sz(get_exec_type(inst));
 }
 
+/**
+ * Return whether the following regioning restriction applies to the specified
+ * instruction.  From the Cherryview PRM Vol 7. "Register Region
+ * Restrictions":
+ *
+ * "When source or destination datatype is 64b or operation is integer DWord
+ *  multiply, regioning in Align1 must follow these rules:
+ *
+ *  1. Source and Destination horizontal stride must be aligned to the same qword.
+ *  2. Regioning must ensure Src.Vstride = Src.Width * Src.Hstride.
+ *  3. Source and Destination offset must be the same, except the case of
+ *     scalar source."
+ */
+static inline bool
+has_dst_aligned_region_restriction(const gen_device_info *devinfo,
+                                   const fs_inst *inst)
+{
+   const brw_reg_type exec_type = get_exec_type(inst);
+   const bool is_int_multiply = !brw_reg_type_is_floating_point(exec_type) &&
+         (inst->opcode == BRW_OPCODE_MUL || inst->opcode == BRW_OPCODE_MAD);
+
+   if (type_sz(inst->dst.type) > 4 || type_sz(exec_type) > 4 ||
+       (type_sz(exec_type) == 4 && is_int_multiply))
+      return devinfo->is_cherryview || gen_device_info_is_9lp(devinfo);
+   else
+      return false;
+}
+
 #endif
-- 
2.19.2