[MLIR] Replace std ops with arith dialect ops

Precursor: https://reviews.llvm.org/D110200

Removed redundant ops from the standard dialect that were moved to the
`arith` or `math` dialects.

Renamed all instances of operations in the codebase and in tests.

Reviewed By: rriddle, jpienaar

Differential Revision: https://reviews.llvm.org/D110797
diff --git a/mlir/test/Conversion/OpenMPToLLVM/convert-to-llvmir.mlir b/mlir/test/Conversion/OpenMPToLLVM/convert-to-llvmir.mlir
index f572935..e3ed2a2 100644
--- a/mlir/test/Conversion/OpenMPToLLVM/convert-to-llvmir.mlir
+++ b/mlir/test/Conversion/OpenMPToLLVM/convert-to-llvmir.mlir
@@ -15,8 +15,8 @@
 
 // CHECK-LABEL: llvm.func @branch_loop
 func @branch_loop() {
-  %start = constant 0 : index
-  %end = constant 0 : index
+  %start = arith.constant 0 : index
+  %end = arith.constant 0 : index
   // CHECK: omp.parallel
   omp.parallel {
     // CHECK-NEXT: llvm.br ^[[BB1:.*]](%{{[0-9]+}}, %{{[0-9]+}} : i64, i64
@@ -24,7 +24,7 @@
   // CHECK-NEXT: ^[[BB1]](%[[ARG1:[0-9]+]]: i64, %[[ARG2:[0-9]+]]: i64):{{.*}}
   ^bb1(%0: index, %1: index):
     // CHECK-NEXT: %[[CMP:[0-9]+]] = llvm.icmp "slt" %[[ARG1]], %[[ARG2]] : i64
-    %2 = cmpi slt, %0, %1 : index
+    %2 = arith.cmpi slt, %0, %1 : index
     // CHECK-NEXT: llvm.cond_br %[[CMP]], ^[[BB2:.*]](%{{[0-9]+}}, %{{[0-9]+}} : i64, i64), ^[[BB3:.*]]
     cond_br %2, ^bb2(%end, %end : index, index), ^bb3
   // CHECK-NEXT: ^[[BB2]](%[[ARG3:[0-9]+]]: i64, %[[ARG4:[0-9]+]]: i64):