[GlobalOptimization] Add a pass to do horizontal fusion of contractio…

…n operations with a common operand. (iree-org#17059)

This pass does a one-off horizontal fusion of contraction operations
with one common operand. It handles the case where the contraction
might be followed by a truncate operation (when the contraction is
done at higher precision, but final result is in lower precision
typical of quantized models).

The pass is off by default and can be enabled by
`--iree-global-opt-fuse-horizontal-contractions`.

Note this pass might be better off being in Preprocessing.

Co-authored-by: Quinn Dawkins <quinn.dawkins@gmail.com>
Co-authored-by: MaheshRavishankar <mahesh@nod-labs.com>

Co-authored-by: Quinn Dawkins <quinn.dawkins@gmail.com>

compiler/src/iree/compiler/GlobalOptimization/BUILD.bazel

@@ -54,6 +54,7 @@ iree_compiler_cc_library(
         "EraseUnusedLinalgOperands.cpp",
         "ExpandTensorShapes.cpp",
         "FuseDequantizationMatmul.cpp",
+        "FuseHorizontalContractions.cpp",
         "FuseSiluHorizontalMatmul.cpp",
         "GeneralizeLinalgNamedOps.cpp",
         "GlobalLoopInvariantCodeMotion.cpp",

compiler/src/iree/compiler/GlobalOptimization/CMakeLists.txt

@@ -50,6 +50,7 @@ iree_cc_library(
     "EraseUnusedLinalgOperands.cpp"
     "ExpandTensorShapes.cpp"
     "FuseDequantizationMatmul.cpp"
+    "FuseHorizontalContractions.cpp"
     "FuseSiluHorizontalMatmul.cpp"
     "GeneralizeLinalgNamedOps.cpp"
     "GlobalLoopInvariantCodeMotion.cpp"