[llvm] [IPO] Added attributor for identifying invariant loads (PR #141800)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,220 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=attributor %s -S | FileCheck %s
+
+ at G = global i32 zeroinitializer, align 4
+
+declare ptr @get_ptr()
+declare noalias ptr @get_noalias_ptr()
+
+define i32 @test_plain(ptr %ptr) {
+; CHECK-LABEL: define i32 @test_plain(
+; CHECK-SAME: ptr nofree noundef nonnull readonly align 4 captures(none) dereferenceable(4) [[PTR:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:    [[VAL:%.*]] = load i32, ptr [[PTR]], align 4
+; CHECK-NEXT:    ret i32 [[VAL]]
+;
+  %val = load i32, ptr %ptr, align 4
+  ret i32 %val
+}
+
+define i32 @test_noalias_ptr(ptr noalias %ptr) {
+; CHECK-LABEL: define i32 @test_noalias_ptr(
+; CHECK-SAME: ptr noalias nofree noundef nonnull readonly align 4 captures(none) dereferenceable(4) [[PTR:%.*]]) #[[ATTR0]] {
+; CHECK-NEXT:    [[VAL:%.*]] = load i32, ptr [[PTR]], align 4, !invariant.load [[META0:![0-9]+]]
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arsenm wrote:

readonly doesn't imply the memory doesn't change, it only states that the function does not write through a reference derived from this argument. I don't think the AA property does anything here


https://github.com/llvm/llvm-project/pull/141800