[llvm] [Analysis] Add new function isDereferenceableReadOnlyLoop (PR #97292)

[David Sherwood via llvm-commits]

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@@ -114,3 +119,86 @@ define void @f(i32* %p1, i32* %p2, i64 %i) {
   EXPECT_TRUE(canReplacePointersInUseIfEqual(PtrToIntUse, P2, DL));
   EXPECT_TRUE(canReplacePointersInUseIfEqual(IcmpUse, P2, DL));
 }
+
+TEST(LoadsTest, IsDerefReadOnlyLoop) {
+  LLVMContext C;
+  std::unique_ptr<Module> M = parseIR(C,
+                                      R"IR(
+define i64 @f1() {
+entry:
+  %p1 = alloca [1024 x i8]
+  %p2 = alloca [1024 x i8]
+  br label %loop
+
+loop:
+  %index = phi i64 [ %index.next, %loop.inc ], [ 3, %entry ]
+  %arrayidx = getelementptr inbounds i8, ptr %p1, i64 %index
+  %ld1 = load i8, ptr %arrayidx, align 1
+  %arrayidx1 = getelementptr inbounds i8, ptr %p2, i64 %index
+  %ld2 = load i8, ptr %arrayidx1, align 1
+  %cmp3 = icmp eq i8 %ld1, %ld2
+  br i1 %cmp3, label %loop.inc, label %loop.end
+
+loop.inc:
+  %index.next = add i64 %index, 1
+  %exitcond = icmp ne i64 %index.next, 67
+  br i1 %exitcond, label %loop, label %loop.end
+
+loop.end:
+  %retval = phi i64 [ %index, %loop ], [ 67, %loop.inc ]
+  ret i64 %retval
+}
+
+define i64 @f2(ptr %p1) {
+entry:
+  %p2 = alloca [1024 x i8]
+  br label %loop
+
+loop:
+  %index = phi i64 [ %index.next, %loop.inc ], [ 3, %entry ]
+  %arrayidx = getelementptr inbounds i8, ptr %p1, i64 %index
+  %ld1 = load i8, ptr %arrayidx, align 1
+  %arrayidx1 = getelementptr inbounds i8, ptr %p2, i64 %index
+  %ld2 = load i8, ptr %arrayidx1, align 1
+  %cmp3 = icmp eq i8 %ld1, %ld2
+  br i1 %cmp3, label %loop.inc, label %loop.end
+
+loop.inc:
+  %index.next = add i64 %index, 1
+  %exitcond = icmp ne i64 %index.next, 67
+  br i1 %exitcond, label %loop, label %loop.end
+
+loop.end:
+  %retval = phi i64 [ %index, %loop ], [ 67, %loop.inc ]
+  ret i64 %retval
+}
+)IR");
+  auto *GV1 = M->getNamedValue("f1");
+  auto *GV2 = M->getNamedValue("f2");
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david-arm wrote:

Done!

https://github.com/llvm/llvm-project/pull/97292