[llvm] [DA] Add tests where dependencies are missed due to overflow (NFC) (PR #164246)

[Michael Kruse via llvm-commits]

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@@ -0,0 +1,137 @@
+; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py UTC_ARGS: --version 6
+; RUN: opt < %s -disable-output "-passes=print<da>" 2>&1 \
+; RUN:     | FileCheck %s --check-prefixes=CHECK,CHECK-ALL
+; RUN: opt < %s -disable-output "-passes=print<da>" -da-enable-dependence-test=symbolic-rdiv 2>&1 \
+; RUN:     | FileCheck %s --check-prefixes=CHECK,CHECK-SYMBOLIC-RDIV
+
+; for (i = 0; i < (1LL << 62); i++) {
+;   if (0 <= 2*i - 2)
+;     A[2*i - 2] = 1;
+;   A[i] = 2;
+; }
+;
+; FIXME: DependenceAnalysis currently detects no dependency between the two
+; stores, but it does exist. For example, each store will access A[0] when i
+; is 1 and 0 respectively.
+; The root cause is that the product of the BTC and the coefficient 
+; ((1LL << 62) - 1 and 2) overflows in a signed sense.
+define void @symbolicrdiv_prod_ovfl(ptr %A) {
+; CHECK-ALL-LABEL: 'symbolicrdiv_prod_ovfl'
+; CHECK-ALL-NEXT:  Src: store i8 1, ptr %gep.0, align 1 --> Dst: store i8 1, ptr %gep.0, align 1
+; CHECK-ALL-NEXT:    da analyze - none!
+; CHECK-ALL-NEXT:  Src: store i8 1, ptr %gep.0, align 1 --> Dst: store i8 2, ptr %gep.1, align 1
+; CHECK-ALL-NEXT:    da analyze - none!
+; CHECK-ALL-NEXT:  Src: store i8 2, ptr %gep.1, align 1 --> Dst: store i8 2, ptr %gep.1, align 1
+; CHECK-ALL-NEXT:    da analyze - none!
+;
+; CHECK-SYMBOLIC-RDIV-LABEL: 'symbolicrdiv_prod_ovfl'
+; CHECK-SYMBOLIC-RDIV-NEXT:  Src: store i8 1, ptr %gep.0, align 1 --> Dst: store i8 1, ptr %gep.0, align 1
+; CHECK-SYMBOLIC-RDIV-NEXT:    da analyze - none!
+; CHECK-SYMBOLIC-RDIV-NEXT:  Src: store i8 1, ptr %gep.0, align 1 --> Dst: store i8 2, ptr %gep.1, align 1
+; CHECK-SYMBOLIC-RDIV-NEXT:    da analyze - none!
+; CHECK-SYMBOLIC-RDIV-NEXT:  Src: store i8 2, ptr %gep.1, align 1 --> Dst: store i8 2, ptr %gep.1, align 1
+; CHECK-SYMBOLIC-RDIV-NEXT:    da analyze - consistent output [*]!
+;
+entry:
+  br label %loop.header
+
+loop.header:
+  %i = phi i64 [ 0, %entry ], [ %i.inc, %loop.latch ]
+  %offset = phi i64 [ -2, %entry ], [ %offset.next, %loop.latch ]
+  %ec = icmp eq i64 %i, 4611686018427387904
+  br i1 %ec, label %exit, label %loop.body
+
+loop.body:
+  %cond = icmp sge i64 %offset, 0
+  br i1 %cond, label %if.then, label %loop.latch
+
+if.then:
+  %gep.0 = getelementptr inbounds i8, ptr %A, i64 %offset
+  store i8 1, ptr %gep.0
+  br label %loop.latch
+
+loop.latch:
+  %gep.1 = getelementptr inbounds i8, ptr %A, i64 %i
+  store i8 2, ptr %gep.1
+  %i.inc = add nuw nsw i64 %i, 1
+  %offset.next = add nsw i64 %offset, 2
+  br label %loop.header
+
+exit:
+  ret void
+}
+
+; offset0 = -4611686018427387904;  // -2^62
+; offset1 =  4611686018427387904;  // 2^62
+; for (i = 0; i < (1LL << 62) - 100; i++) {
+;   if (0 <= offset0)
+;     A[offset0] = 1;
+;   if (0 <= offset1)
+;     A[offset1] = 2;
+;   offset0 += 2;
+;   offset1 -= 1;
+; }
+;
+; FIXME: DependenceAnalysis currently detects no dependency between the two
+; stores, but it does exist. For example,
+;
+;  memory access           | i == 2^61 | i == 2^61 + 2^59 | i == 2^61 + 2^60  
+; -------------------------|-----------|------------------|-------------------
+;  A[2*i - 2^62] (offset0) |           | A[2^60]          | A[2^61]           
+;  A[-i + 2^62]  (offset1) | A[2^61]   |                  | A[2^60]           
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Meinersbur wrote:

👍

https://github.com/llvm/llvm-project/pull/164246