Mesa (master): intel/compiler: Don' t propagate cmod into integer multiplies
Jason Ekstrand
jekstrand at kemper.freedesktop.org
Thu Oct 5 18:55:05 UTC 2017
Module: Mesa
Branch: master
Commit: 7463d5058009d1e9d9d01292f894271a26a062b8
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=7463d5058009d1e9d9d01292f894271a26a062b8
Author: Jason Ekstrand <jason.ekstrand at intel.com>
Date: Wed Oct 4 13:20:52 2017 -0700
intel/compiler: Don't propagate cmod into integer multiplies
No shader-db change on Sky Lake.
Reviewed-by: Matt Turner <mattst88 at gmail.com>
Cc: mesa-stable at lists.freedesktop.org
---
src/intel/compiler/brw_fs_cmod_propagation.cpp | 17 +++++++++++++++++
src/intel/compiler/brw_vec4_cmod_propagation.cpp | 17 +++++++++++++++++
2 files changed, 34 insertions(+)
diff --git a/src/intel/compiler/brw_fs_cmod_propagation.cpp b/src/intel/compiler/brw_fs_cmod_propagation.cpp
index db63e942b7..4625d69f89 100644
--- a/src/intel/compiler/brw_fs_cmod_propagation.cpp
+++ b/src/intel/compiler/brw_fs_cmod_propagation.cpp
@@ -150,6 +150,23 @@ opt_cmod_propagation_local(const gen_device_info *devinfo, bblock_t *block)
if (scan_inst->saturate)
break;
+ /* From the Sky Lake PRM, Vol 2a, "Multiply":
+ *
+ * "When multiplying integer data types, if one of the sources
+ * is a DW, the resulting full precision data is stored in
+ * the accumulator. However, if the destination data type is
+ * either W or DW, the low bits of the result are written to
+ * the destination register and the remaining high bits are
+ * discarded. This results in undefined Overflow and Sign
+ * flags. Therefore, conditional modifiers and saturation
+ * (.sat) cannot be used in this case."
+ *
+ * We just disallow cmod propagation on all integer multiplies.
+ */
+ if (!brw_reg_type_is_floating_point(scan_inst->dst.type) &&
+ scan_inst->opcode == BRW_OPCODE_MUL)
+ break;
+
/* Otherwise, try propagating the conditional. */
enum brw_conditional_mod cond =
inst->src[0].negate ? brw_swap_cmod(inst->conditional_mod)
diff --git a/src/intel/compiler/brw_vec4_cmod_propagation.cpp b/src/intel/compiler/brw_vec4_cmod_propagation.cpp
index 05e6516819..0d72d82a57 100644
--- a/src/intel/compiler/brw_vec4_cmod_propagation.cpp
+++ b/src/intel/compiler/brw_vec4_cmod_propagation.cpp
@@ -137,6 +137,23 @@ opt_cmod_propagation_local(bblock_t *block)
if (scan_inst->saturate)
break;
+ /* From the Sky Lake PRM, Vol 2a, "Multiply":
+ *
+ * "When multiplying integer data types, if one of the sources
+ * is a DW, the resulting full precision data is stored in
+ * the accumulator. However, if the destination data type is
+ * either W or DW, the low bits of the result are written to
+ * the destination register and the remaining high bits are
+ * discarded. This results in undefined Overflow and Sign
+ * flags. Therefore, conditional modifiers and saturation
+ * (.sat) cannot be used in this case.
+ *
+ * We just disallow cmod propagation on all integer multiplies.
+ */
+ if (!brw_reg_type_is_floating_point(scan_inst->dst.type) &&
+ scan_inst->opcode == BRW_OPCODE_MUL)
+ break;
+
/* Otherwise, try propagating the conditional. */
enum brw_conditional_mod cond =
inst->src[0].negate ? brw_swap_cmod(inst->conditional_mod)
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