intel/fs: Constant fold SHL

Without "intel/fs: Combine constants for integer instructions too", this
commit won't do anything.  While looking at one of the shaders hurt by
that commit for instructions, I notied some things like:

    mov(1)          g25.1<1>D       4D
    ...
    shl(8)          g80<1>UD        g25.1<0,1,0>D   0x00000001UD
    or(8)           g11<1>UD        g80<8,8,1>UD    g50<8,8,1>UW
    send(8)         nullUD          g10UD           nullUD          0x060ac2fd                0x00000000
      data MsgDesc: ( DC DWORD scatterd write, 253, 2) mlen 3 ex_mlen 0 rlen 0

This looks like some sort of address or offset calculation that is added
in the backend.

shader-db results:

All Gen8+ platforms had similar results. (Ice Lake shown)
total instructions in shared programs: 20027279 -> 20021249 (-0.03%)
instructions in affected programs: 31442 -> 25412 (-19.18%)
helped: 12
HURT: 0
helped stats (abs) min: 18 max: 1152 x̄: 502.50 x̃: 360
helped stats (rel) min: 5.75% max: 23.87% x̄: 18.73% x̃: 19.06%
95% mean confidence interval for instructions value: -717.87 -287.13
95% mean confidence interval for instructions %-change: -22.00% -15.46%
Instructions are helped.

total cycles in shared programs: 978895243 -> 978872081 (<.01%)
cycles in affected programs: 6528787 -> 6505625 (-0.35%)
helped: 12
HURT: 0
helped stats (abs) min: 60 max: 4298 x̄: 1930.17 x̃: 1691
helped stats (rel) min: 0.06% max: 8.13% x̄: 2.11% x̃: 0.40%
95% mean confidence interval for cycles value: -2745.02 -1115.32
95% mean confidence interval for cycles %-change: -3.99% -0.23%
Cycles are helped.

Haswell
total instructions in shared programs: 16389292 -> 16383768 (-0.03%)
instructions in affected programs: 29757 -> 24233 (-18.56%)
helped: 11
HURT: 0
helped stats (abs) min: 18 max: 1171 x̄: 502.18 x̃: 360
helped stats (rel) min: 5.22% max: 23.90% x̄: 18.30% x̃: 18.25%
95% mean confidence interval for instructions value: -745.63 -258.74
95% mean confidence interval for instructions %-change: -22.08% -14.52%
Instructions are helped.

total cycles in shared programs: 1034797073 -> 1034770429 (<.01%)
cycles in affected programs: 6468869 -> 6442225 (-0.41%)
helped: 11
HURT: 0
helped stats (abs) min: 30 max: 6162 x̄: 2422.18 x̃: 2168
helped stats (rel) min: 0.03% max: 8.14% x̄: 2.17% x̃: 0.55%
95% mean confidence interval for cycles value: -3752.79 -1091.58
95% mean confidence interval for cycles %-change: -4.24% -0.10%
Cycles are helped.

total spills in shared programs: 16509 -> 16503 (-0.04%)
spills in affected programs: 1208 -> 1202 (-0.50%)
helped: 2
HURT: 0

total fills in shared programs: 20255 -> 20239 (-0.08%)
fills in affected programs: 168 -> 152 (-9.52%)
helped: 2
HURT: 0

LOST:   0
GAINED: 2

No changes on any earlier platforms.

fossil-db results:

Tiger Lake
Instructions in all programs: 160832341 -> 160827821 (-0.0%)
SENDs in all programs: 6814052 -> 6814052 (+0.0%)
Loops in all programs: 38224 -> 38224 (+0.0%)
Cycles in all programs: 7635756412 -> 7635807190 (+0.0%)
Spills in all programs: 187040 -> 187040 (+0.0%)
Fills in all programs: 292482 -> 292482 (+0.0%)

Ice Lake
Instructions in all programs: 145135276 -> 145132927 (-0.0%)
SENDs in all programs: 6865190 -> 6865190 (+0.0%)
Loops in all programs: 38219 -> 38219 (+0.0%)
Cycles in all programs: 9028602846 -> 9028597718 (-0.0%)
Spills in all programs: 206953 -> 206953 (+0.0%)
Fills in all programs: 313159 -> 313159 (+0.0%)

Skylake
Instructions in all programs: 135836531 -> 135834156 (-0.0%)
SENDs in all programs: 6805651 -> 6805651 (+0.0%)
Loops in all programs: 38216 -> 38216 (+0.0%)
Cycles in all programs: 8649436861 -> 8649426779 (-0.0%)
Spills in all programs: 193981 -> 193981 (+0.0%)
Fills in all programs: 300098 -> 300098 (+0.0%)

1 files changed, 24 insertions, 0 deletions

diff --git a/src/intel/compiler/brw_fs.cpp b/src/intel/compiler/brw_fs.cpp
index 41449b7a536..c70a6e6e329 100644
--- a/src/intel/compiler/brw_fs.cpp
+++ b/src/intel/compiler/brw_fs.cpp
@@ -2655,6 +2655,30 @@ fs_visitor::opt_algebraic()
             progress = true;
          }
          break;
+      case BRW_OPCODE_SHL:
+         if (inst->src[0].file == IMM && inst->src[1].file == IMM) {
+            fs_reg result;
+
+            switch (type_sz(inst->src[0].type)) {
+            case 2:
+               result = brw_imm_uw(0x0ffff & (inst->src[0].ud << (inst->src[1].ud & 0x0f)));
+               break;
+            case 4:
+               result = brw_imm_ud(inst->src[0].ud << (inst->src[1].ud & 0x1f));
+               break;
+            case 8:
+               result = brw_imm_uq(inst->src[0].u64 << (inst->src[1].ud & 0x2f));
+               break;
+            }
+
+            inst->opcode = BRW_OPCODE_MOV;
+            inst->src[0] = retype(result, inst->dst.type);
+            inst->src[1] = reg_undef;
+
+            progress = true;
+         }
+         break;
+
       case SHADER_OPCODE_BROADCAST:
          if (is_uniform(inst->src[0])) {
             inst->opcode = BRW_OPCODE_MOV;