added motivation to shift-binop.ll

Author: Charukesh827

llvm/test/Transforms/InstCombine/shift-binop.ll

@@ -1,6 +1,19 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -passes=instcombine -S | FileCheck %s
 
+;define i32 @src(i32 %x, i32 %shamt, i32 %c) {
+;  %shl = shl nuw i32 %x, %shamt
+;  %c2 = shl nuw i32 %c, %shamt
+;  %max = call i32 @llvm.umin(i32 %shl, i32 %c2)
+;  ret i32 %max
+;}
+
+;define i32 @tgt(i32 %x, i32 %shamt, i32 %c) {
+;  %max = call i32 @llvm.umin(i32 %x, i32 %c)
+;  %shl = shl i32 %max, %shamt
+;  ret i32 %shl
+;}
+
 define i8 @src1(i8 %arg0) {
 ; CHECK-LABEL: @src1(
 ; CHECK-NEXT:    [[SHL:%.*]] = shl nuw i8 [[ARG0:%.*]], 1