[RS4GC] Add a test to demonstrate duplication of base generation. NFC

[yrouban]

Summary

This new test demonstrates a case where a base ptr is generated twice for the same value: the first one is generated while the gc.get.pointer.base() is inlined, the second is generated for the statepoint. This happens because the methods inlineGetBaseAndOffset() and insertParsePoints() do not share their defining value cache used by the findBasePointer() method.

[reames]

LGTM.

p.s. This could have landed without review.

llvm/test/Transforms/RewriteStatepointsForGC/intrinsics-bare.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes=rewrite-statepoints-for-gc -S < %s | FileCheck %s
+
+declare i8 addrspace(1)* @llvm.experimental.gc.get.pointer.base.p1i8.p1i8(i8 addrspace(1)* readnone nocapture) nounwind readnone willreturn
+declare void @foo()
+
+define i8 addrspace(1)* @test_duplicate_base_generation(i8 addrspace(1)* %obj1, i8 addrspace(1)* %obj2, i1 %c) gc "statepoint-example" {
+; CHECK-LABEL: @test_duplicate_base_generation(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[OBJ1_12:%.*]] = getelementptr inbounds i8, i8 addrspace(1)* [[OBJ1:%.*]], i64 12
+; CHECK-NEXT:    [[OBJ2_16:%.*]] = getelementptr inbounds i8, i8 addrspace(1)* [[OBJ2:%.*]], i64 16
+; CHECK-NEXT:    [[SELECTED_BASE:%.*]] = select i1 [[C:%.*]], i8 addrspace(1)* [[OBJ2]], i8 addrspace(1)* [[OBJ1]], !is_base_value !0
+; CHECK-NEXT:    [[SELECTED_BASE1:%.*]] = select i1 [[C]], i8 addrspace(1)* [[OBJ2]], i8 addrspace(1)* [[OBJ1]], !is_base_value !0
+; CHECK-NEXT:    [[SELECTED:%.*]] = select i1 [[C]], i8 addrspace(1)* [[OBJ2_16]], i8 addrspace(1)* [[OBJ1_12]]
+; CHECK-NEXT:    [[STATEPOINT_TOKEN:%.*]] = call token (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 2882400000, i32 0, void ()* @foo, i32 0, i32 0, i32 0, i32 0) [ "gc-live"(i8 addrspace(1)* [[SELECTED]], i8 addrspace(1)* [[SELECTED_BASE1]]) ]
+; CHECK-NEXT:    [[SELECTED_RELOCATED:%.*]] = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(token [[STATEPOINT_TOKEN]], i32 1, i32 0)
+; CHECK-NEXT:    [[SELECTED_BASE1_RELOCATED:%.*]] = call coldcc i8 addrspace(1)* @llvm.experimental.gc.relocate.p1i8(token [[STATEPOINT_TOKEN]], i32 1, i32 1)
+; CHECK-NEXT:    ret i8 addrspace(1)* [[SELECTED_RELOCATED]]
+;
+entry:
+  %obj1.12 = getelementptr inbounds i8, i8 addrspace(1)* %obj1, i64 12
+  %obj2.16 = getelementptr inbounds i8, i8 addrspace(1)* %obj2, i64 16
+  %selected = select i1 %c, i8 addrspace(1)* %obj2.16, i8 addrspace(1)* %obj1.12
+  %base = call i8 addrspace(1)* @llvm.experimental.gc.get.pointer.base.p1i8.p1i8(i8 addrspace(1)* %selected)
+  call void @foo()
+  ret i8 addrspace(1)* %selected
+}