[BasicAA] Add additional truncation tests (NFC)

These show that the known bits and non-zero heuristics are incorrect
when truncation is involved.

diff --git a/llvm/test/Analysis/BasicAA/gep-implicit-trunc-32-bit-pointers.ll b/llvm/test/Analysis/BasicAA/gep-implicit-trunc-32-bit-pointers.ll
index 5e02fbd..4b55986 100644 (file)
--- a/llvm/test/Analysis/BasicAA/gep-implicit-trunc-32-bit-pointers.ll
+++ b/llvm/test/Analysis/BasicAA/gep-implicit-trunc-32-bit-pointers.ll
@@ -66,3 +66,32 @@ define void @mustalias_overflow_in_32_bit_add_mul_gep(i8* %ptr, i64 %i) {
   store i8 1, i8* %gep.2
   ret void
 }
+
+; FIXME: While %n is non-zero, its low 32 bits may not be.
+define void @mayalias_overflow_in_32_bit_non_zero(i8* %ptr, i64 %n) {
+; CHECK-LABEL: Function: mayalias_overflow_in_32_bit_non_zero
+; CHECK:    NoAlias: i8* %gep, i8* %ptr
+;
+  %c = icmp ne i64 %n, 0
+  call void @llvm.assume(i1 %c)
+  store i8 0, i8* %ptr
+  %gep = getelementptr i8, i8* %ptr, i64 %n
+  store i8 1, i8* %gep
+  ret void
+}
+
+; FIXME: While %n is positive, its low 32 bits may not be.
+define void @mayalias_overflow_in_32_bit_positive(i8* %ptr, i64 %n) {
+; CHECK-LABEL: Function: mayalias_overflow_in_32_bit_positive
+; CHECK:    NoAlias: i8* %gep.1, i8* %ptr
+; CHECK:    NoAlias: i8* %gep.2, i8* %ptr
+; CHECK:    NoAlias: i8* %gep.1, i8* %gep.2
+;
+  %c = icmp sgt i64 %n, 0
+  call void @llvm.assume(i1 %c)
+  %gep.1 = getelementptr i8, i8* %ptr, i64 -1
+  store i8 0, i8* %gep.1
+  %gep.2 = getelementptr i8, i8* %ptr, i64 %n
+  store i8 1, i8* %gep.2
+  ret void
+}