Mesa (master): nir/lower_bit_size: fix lowering of {imul,umul}_high

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Module: Mesa
Branch: master
Commit: 6d792989924ce79363f181462904fa46692a99b5
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=6d792989924ce79363f181462904fa46692a99b5

Author: Rhys Perry <pendingchaos02 at gmail.com>
Date:   Tue Mar 31 13:52:43 2020 +0100

nir/lower_bit_size: fix lowering of {imul,umul}_high

Signed-off-by: Rhys Perry <pendingchaos02 at gmail.com>
Reviewed-by: Erik Faye-Lund <erik.faye-lund at collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4387>

---

 src/compiler/nir/nir_lower_bit_size.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/compiler/nir/nir_lower_bit_size.c b/src/compiler/nir/nir_lower_bit_size.c
index 3ba63c81adc..100ac4864a5 100644
--- a/src/compiler/nir/nir_lower_bit_size.c
+++ b/src/compiler/nir/nir_lower_bit_size.c
@@ -70,8 +70,18 @@ lower_instr(nir_builder *bld, nir_alu_instr *alu, unsigned bit_size)
    }
 
    /* Emit the lowered ALU instruction */
-   nir_ssa_def *lowered_dst =
-      nir_build_alu(bld, op, srcs[0], srcs[1], srcs[2], srcs[3]);
+   nir_ssa_def *lowered_dst = NULL;
+   if (op == nir_op_imul_high || op == nir_op_umul_high) {
+      assert(dst_bit_size * 2 <= bit_size);
+      nir_ssa_def *lowered_dst = nir_imul(bld, srcs[0], srcs[1]);
+      if (nir_op_infos[op].output_type & nir_type_uint)
+         lowered_dst = nir_ushr(bld, lowered_dst, nir_imm_int(bld, dst_bit_size));
+      else
+         lowered_dst = nir_ishr(bld, lowered_dst, nir_imm_int(bld, dst_bit_size));
+   } else {
+      lowered_dst = nir_build_alu(bld, op, srcs[0], srcs[1], srcs[2], srcs[3]);
+   }
+
 
    /* Convert result back to the original bit-size */
    nir_alu_type type = nir_op_infos[op].output_type;