Mesa (master): nir/builder: Emit better code for iadd/imul_imm

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Module: Mesa
Branch: master
Commit: cd4c1458baba595aaff25ca1099c60a57d31772b
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=cd4c1458baba595aaff25ca1099c60a57d31772b

Author: Jason Ekstrand <jason.ekstrand at intel.com>
Date:   Wed Mar  6 12:27:26 2019 -0600

nir/builder: Emit better code for iadd/imul_imm

Because we already know the immediate right-hand parameter, we can
potentially save the optimizer a bit of work.

Reviewed-by: Karol Herbst <kherbst at redhat.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira at intel.com>

---

 src/compiler/nir/nir_builder.h     | 25 +++++++++++++++++++++++--
 src/compiler/spirv/vtn_variables.c |  4 +---
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/src/compiler/nir/nir_builder.h b/src/compiler/nir/nir_builder.h
index 43edf0a9d36..42004a2fe54 100644
--- a/src/compiler/nir/nir_builder.h
+++ b/src/compiler/nir/nir_builder.h
@@ -25,6 +25,7 @@
 #define NIR_BUILDER_H
 
 #include "nir_control_flow.h"
+#include "util/bitscan.h"
 #include "util/half_float.h"
 
 struct exec_list;
@@ -601,13 +602,33 @@ nir_u2u(nir_builder *build, nir_ssa_def *x, unsigned dest_bit_size)
 static inline nir_ssa_def *
 nir_iadd_imm(nir_builder *build, nir_ssa_def *x, uint64_t y)
 {
-   return nir_iadd(build, x, nir_imm_intN_t(build, y, x->bit_size));
+   assert(x->bit_size <= 64);
+   if (x->bit_size < 64)
+      y &= (1ull << x->bit_size) - 1;
+
+   if (y == 0) {
+      return x;
+   } else {
+      return nir_iadd(build, x, nir_imm_intN_t(build, y, x->bit_size));
+   }
 }
 
 static inline nir_ssa_def *
 nir_imul_imm(nir_builder *build, nir_ssa_def *x, uint64_t y)
 {
-   return nir_imul(build, x, nir_imm_intN_t(build, y, x->bit_size));
+   assert(x->bit_size <= 64);
+   if (x->bit_size < 64)
+      y &= (1ull << x->bit_size) - 1;
+
+   if (y == 0) {
+      return nir_imm_intN_t(build, 0, x->bit_size);
+   } else if (y == 1) {
+      return x;
+   } else if (util_is_power_of_two_or_zero64(y)) {
+      return nir_ishl(build, x, nir_imm_int(build, ffsll(y) - 1));
+   } else {
+      return nir_imul(build, x, nir_imm_intN_t(build, y, x->bit_size));
+   }
 }
 
 static inline nir_ssa_def *
diff --git a/src/compiler/spirv/vtn_variables.c b/src/compiler/spirv/vtn_variables.c
index d8a4407639f..c3ce15aaaaf 100644
--- a/src/compiler/spirv/vtn_variables.c
+++ b/src/compiler/spirv/vtn_variables.c
@@ -79,9 +79,7 @@ vtn_access_link_as_ssa(struct vtn_builder *b, struct vtn_access_link link,
       nir_ssa_def *ssa = vtn_ssa_value(b, link.id)->def;
       if (ssa->bit_size != bit_size)
          ssa = nir_i2i(&b->nb, ssa, bit_size);
-      if (stride != 1)
-         ssa = nir_imul_imm(&b->nb, ssa, stride);
-      return ssa;
+      return nir_imul_imm(&b->nb, ssa, stride);
    }
 }