[llvm] f7fb467 - [DA] Add a test where the Weak Crossing SIV test misses dependency (NFC) (#188183)

[via llvm-commits]

Author: Ryotaro Kasuga
Date: 2026-03-24T07:08:15Z
New Revision: f7fb46701a374d2a15d9e79197f21b128e249b95

URL: https://github.com/llvm/llvm-project/commit/f7fb46701a374d2a15d9e79197f21b128e249b95
DIFF: https://github.com/llvm/llvm-project/commit/f7fb46701a374d2a15d9e79197f21b128e249b95.diff

LOG: [DA] Add a test where the Weak Crossing SIV test misses dependency (NFC) (#188183)

The root cause is that the Weak Crossing SIV test assumes the
coefficients are non‑zero without verifying it.

Added: 
    llvm/test/Analysis/DependenceAnalysis/weak-crossing-siv-coeff-may-zero.ll

Modified: 
    

Removed: 
    


################################################################################
diff  --git a/llvm/test/Analysis/DependenceAnalysis/weak-crossing-siv-coeff-may-zero.ll b/llvm/test/Analysis/DependenceAnalysis/weak-crossing-siv-coeff-may-zero.ll
new file mode 100644
index 0000000000000..d4a0fd12343fa
--- /dev/null
+++ b/llvm/test/Analysis/DependenceAnalysis/weak-crossing-siv-coeff-may-zero.ll
@@ -0,0 +1,58 @@
+; 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=weak-crossing-siv 2>&1 \
+; RUN:     | FileCheck %s --check-prefixes=CHECK,CHECK-WEAK-CROSSING-SIV
+
+; for (i = 0; i < 10; i++) {
+;   A[a*i] = 0;
+;   A[-a*i] = 1;
+; }
+;
+; FIXME: When a == 0, there is a dependency with all directions between the two
+; stores.
+;
+define void @weak_crossing_siv_coeff_may_zero(ptr %A, i64 %a) {
+; CHECK-ALL-LABEL: 'weak_crossing_siv_coeff_may_zero'
+; CHECK-ALL-NEXT:  Src: store i8 0, ptr %gep.0, align 1 --> Dst: store i8 0, ptr %gep.0, align 1
+; CHECK-ALL-NEXT:    da analyze - output [0]!
+; CHECK-ALL-NEXT:    Runtime Assumptions:
+; CHECK-ALL-NEXT:    Compare predicate: %a ne) 0
+; CHECK-ALL-NEXT:  Src: store i8 0, ptr %gep.0, align 1 --> Dst: store i8 1, ptr %gep.1, align 1
+; CHECK-ALL-NEXT:    da analyze - output [0|<]!
+; CHECK-ALL-NEXT:  Src: store i8 1, ptr %gep.1, align 1 --> Dst: store i8 1, ptr %gep.1, align 1
+; CHECK-ALL-NEXT:    da analyze - output [0]!
+; CHECK-ALL-NEXT:    Runtime Assumptions:
+; CHECK-ALL-NEXT:    Compare predicate: (-1 * %a) ne) 0
+;
+; CHECK-WEAK-CROSSING-SIV-LABEL: 'weak_crossing_siv_coeff_may_zero'
+; CHECK-WEAK-CROSSING-SIV-NEXT:  Src: store i8 0, ptr %gep.0, align 1 --> Dst: store i8 0, ptr %gep.0, align 1
+; CHECK-WEAK-CROSSING-SIV-NEXT:    da analyze - output [*]!
+; CHECK-WEAK-CROSSING-SIV-NEXT:  Src: store i8 0, ptr %gep.0, align 1 --> Dst: store i8 1, ptr %gep.1, align 1
+; CHECK-WEAK-CROSSING-SIV-NEXT:    da analyze - output [0|<]!
+; CHECK-WEAK-CROSSING-SIV-NEXT:  Src: store i8 1, ptr %gep.1, align 1 --> Dst: store i8 1, ptr %gep.1, align 1
+; CHECK-WEAK-CROSSING-SIV-NEXT:    da analyze - output [*]!
+;
+entry:
+  %a.neg = sub nsw i64 0, %a
+  br label %loop
+
+loop:
+  %i = phi i64 [ 0, %entry ], [ %i.inc, %loop ]
+  %offset.0 = phi i64 [ 0, %entry ], [ %offset.0.next, %loop ]
+  %offset.1 = phi i64 [ 0, %entry ], [ %offset.1.next, %loop ]
+  %gep.0 = getelementptr i8, ptr %A, i64 %offset.0
+  %gep.1 = getelementptr i8, ptr %A, i64 %offset.1
+  store i8 0, ptr %gep.0
+  store i8 1, ptr %gep.1
+  %i.inc = add i64 %i, 1
+  %offset.0.next = add nsw i64 %offset.0, %a
+  %offset.1.next = add nsw i64 %offset.1, %a.neg
+  %ec = icmp eq i64 %i.inc, 10
+  br i1 %ec, label %exit, label %loop
+
+exit:
+  ret void
+}
+;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
+; CHECK: {{.*}}