[InstCombine] Add pre-commit tests. NFC.

Author: dtcxzyw

llvm/test/Transforms/InstCombine/pr142518.ll

@@ -0,0 +1,39 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=instcombine < %s | FileCheck %s
+
+define i8 @pr142518(ptr %p, i8 %x, i1 %c) {
+; CHECK-LABEL: define i8 @pr142518(
+; CHECK-SAME: ptr [[P:%.*]], i8 [[X:%.*]], i1 [[C:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i8 [[X]], -2
+; CHECK-NEXT:    br label %[[LOOP:.*]]
+; CHECK:       [[LOOP]]:
+; CHECK-NEXT:    [[EXT2:%.*]] = zext i1 [[CMP]] to i8
+; CHECK-NEXT:    store i8 [[EXT2]], ptr [[P]], align 1
+; CHECK-NEXT:    br i1 false, label %[[LOOP]], label %[[EXIT:.*]]
+; CHECK:       [[EXIT]]:
+; CHECK-NEXT:    [[EXT3:%.*]] = zext i1 [[CMP]] to i8
+; CHECK-NEXT:    ret i8 [[EXT3]]
+;
+entry:
+  %flag = alloca i8, align 1
+  %cmp = icmp slt i8 %x, -1
+  br label %loop
+
+loop:
+  %phi = phi i1 [ %cmp, %entry ], [ %c, %loop ]
+  %not1 = xor i1 %phi, true
+  %or = or i1 %cmp, %not1
+  %not2 = xor i1 %or, true
+  %ext2 = zext i1 %not2 to i8
+  store i8 %ext2, ptr %p, align 1
+  store i8 1, ptr %flag, align 1
+  %flagv = load i8, ptr %flag, align 1
+  %cond = icmp eq i8 %flagv, 0
+  br i1 %cond, label %loop, label %exit
+
+exit:
+  %not3 = xor i1 %or, true
+  %ext3 = zext i1 %not3 to i8
+  ret i8 %ext3
+}