forked from OSchip/llvm-project
[instcombine] Add test coverage for a tricky bit of reasoning about unescaped mallocs
This commit is contained in:
Philip Reames
parent
4745c994e4
commit
57a6d92163
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@ -203,4 +203,120 @@ define i1 @compare_distinct_pointer_escape() {
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ret i1 %cmp
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}
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; The next block of tests demonstrate a very subtle correctness requirement.
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; We can generally assume any *single* heap layout we chose for the result of
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; a malloc call, but we can't simultanious assume two different ones. As a
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; result, we must make sure that we only fold conditions if we can ensure that
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; we fold *all* potentially address capturing compares the same. This is
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; the same point that applies to allocas, applied to noaiias/malloc.
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; These two functions represents either a) forging a pointer via inttoptr or
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; b) indexing off an adjacent allocation. In either case, the operation is
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; obscured by an uninlined helper and not visible to instcombine.
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declare i8* @hidden_inttoptr()
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declare i8* @hidden_offset(i8* %other)
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; FIXME: Missed oppurtunity
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define i1 @ptrtoint_single_cmp() {
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; CHECK-LABEL: @ptrtoint_single_cmp(
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; CHECK-NEXT: [[M:%.*]] = call dereferenceable_or_null(4) i8* @malloc(i64 4)
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; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8* [[M]], inttoptr (i64 2048 to i8*)
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%m = call i8* @malloc(i64 4)
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%rhs = inttoptr i64 2048 to i8*
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%cmp = icmp eq i8* %m, %rhs
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ret i1 %cmp
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}
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define i1 @offset_single_cmp() {
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; CHECK-LABEL: @offset_single_cmp(
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; CHECK-NEXT: ret i1 false
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;
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%m = call i8* @malloc(i64 4)
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%n = call i8* @malloc(i64 4)
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%rhs = getelementptr i8, i8* %n, i32 4
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%cmp = icmp eq i8* %m, %rhs
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ret i1 %cmp
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}
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define i1 @neg_consistent_fold1() {
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; CHECK-LABEL: @neg_consistent_fold1(
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; CHECK-NEXT: [[M:%.*]] = call dereferenceable_or_null(4) i8* @malloc(i64 4)
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; CHECK-NEXT: [[RHS2:%.*]] = call i8* @hidden_inttoptr()
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; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i8* [[M]], inttoptr (i64 2048 to i8*)
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; CHECK-NEXT: [[TMP1:%.*]] = icmp eq i8* [[RHS2]], inttoptr (i64 2048 to i8*)
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; CHECK-NEXT: [[TMP2:%.*]] = and i1 [[CMP1]], [[TMP1]]
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; CHECK-NEXT: ret i1 [[TMP2]]
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;
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%m = call i8* @malloc(i64 4)
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%rhs = inttoptr i64 2048 to i8*
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%rhs2 = call i8* @hidden_inttoptr()
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%cmp1 = icmp eq i8* %m, %rhs
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%cmp2 = icmp eq i8* %m, %rhs2
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%res = and i1 %cmp1, %cmp2
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ret i1 %res
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}
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define i1 @neg_consistent_fold2() {
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; CHECK-LABEL: @neg_consistent_fold2(
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; CHECK-NEXT: [[M:%.*]] = call dereferenceable_or_null(4) i8* @malloc(i64 4)
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; CHECK-NEXT: [[N:%.*]] = call dereferenceable_or_null(4) i8* @malloc(i64 4)
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; CHECK-NEXT: [[RHS:%.*]] = getelementptr i8, i8* [[N]], i64 4
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; CHECK-NEXT: [[RHS2:%.*]] = call i8* @hidden_offset(i8* [[N]])
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; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i8* [[M]], [[RHS]]
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; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i8* [[M]], [[RHS2]]
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; CHECK-NEXT: [[RES:%.*]] = and i1 [[CMP1]], [[CMP2]]
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; CHECK-NEXT: ret i1 [[RES]]
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;
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%m = call i8* @malloc(i64 4)
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%n = call i8* @malloc(i64 4)
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%rhs = getelementptr i8, i8* %n, i32 4
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%rhs2 = call i8* @hidden_offset(i8* %n)
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%cmp1 = icmp eq i8* %m, %rhs
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%cmp2 = icmp eq i8* %m, %rhs2
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%res = and i1 %cmp1, %cmp2
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ret i1 %res
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}
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define i1 @neg_consistent_fold3() {
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; CHECK-LABEL: @neg_consistent_fold3(
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; CHECK-NEXT: [[M:%.*]] = call dereferenceable_or_null(4) i8* @malloc(i64 4)
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; CHECK-NEXT: [[BC:%.*]] = bitcast i8* [[M]] to i32*
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; CHECK-NEXT: [[LGP:%.*]] = load i32*, i32** @gp, align 8
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; CHECK-NEXT: [[RHS2:%.*]] = call i8* @hidden_inttoptr()
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; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i32* [[LGP]], [[BC]]
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; CHECK-NEXT: [[CMP2:%.*]] = icmp eq i8* [[M]], [[RHS2]]
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; CHECK-NEXT: [[RES:%.*]] = and i1 [[CMP1]], [[CMP2]]
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; CHECK-NEXT: ret i1 [[RES]]
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;
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%m = call i8* @malloc(i64 4)
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%bc = bitcast i8* %m to i32*
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%lgp = load i32*, i32** @gp, align 8
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%rhs2 = call i8* @hidden_inttoptr()
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%cmp1 = icmp eq i32* %bc, %lgp
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%cmp2 = icmp eq i8* %m, %rhs2
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%res = and i1 %cmp1, %cmp2
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ret i1 %res
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}
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; FIXME: This appears correct, but the current implementation relies
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; on visiting both cmps in the same pass. We may have an simplification order
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; under which one is missed, and that would be a bug.
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define i1 @neg_consistent_fold4() {
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; CHECK-LABEL: @neg_consistent_fold4(
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; CHECK-NEXT: ret i1 false
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;
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%m = call i8* @malloc(i64 4)
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%bc = bitcast i8* %m to i32*
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%lgp = load i32*, i32** @gp, align 8
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%cmp1 = icmp eq i32* %bc, %lgp
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%cmp2 = icmp eq i32* %bc, %lgp
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%res = and i1 %cmp1, %cmp2
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ret i1 %res
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}
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!0 = !{}
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