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[DA] Add test for GCD MIV misses dependency due to overflow (NFC) #172002

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[DA] Add test for GCD MIV misses dependency due to overflow (NFC) #172002

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[DA] Add test for GCD MIV misses dependency due to overflow (NFC)
kasuga-fj Dec 12, 2025
41e39ed
fix miscalculation
kasuga-fj Dec 16, 2025
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84 changes: 84 additions & 0 deletions llvm/test/Analysis/DependenceAnalysis/gcd-miv-overflow.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -179,5 +179,89 @@ loop:
exit:
ret void
}

; // 5*1844674407370955161 == 9223372036854775805 == INT64_MAX - 2, so addrecs don't overflow.
;
; for (i = 0; i < 1844674407370955162; i++)
; for (j = 0; j < 2; j++) {
; offset0 = 5*i - 9223372036854775805*j;
; offset1 = -5*i + 9223372036854775796*j - 1;
; if (offset0 == -5) A[offset0] = 0;
; if (offset1 == -5) A[offset1] = 0;
; }
;
; FIXME: DependenceAnalysis fails to detect dependency between two stores. Also
; GCD MIV misses '='-dependency.
;
; memory accesses | (i,j) == (1844674407370955160,1)
; ------------------------------------|----------------------------------
; A[ 5*i - 9223372036854775805*j] | A[-5]
; A[-5*i + 9223372036854775796*j - 1] | A[-5]
;
define void @gcdmiv_delta_ovfl2(ptr %A) {
; CHECK-ALL-LABEL: 'gcdmiv_delta_ovfl2'
; 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 - none!
; CHECK-ALL-NEXT: Src: store i8 0, ptr %gep.0, align 1 --> Dst: store i8 0, ptr %gep.1, align 1
; CHECK-ALL-NEXT: da analyze - none!
; CHECK-ALL-NEXT: Src: store i8 0, ptr %gep.1, align 1 --> Dst: store i8 0, ptr %gep.1, align 1
; CHECK-ALL-NEXT: da analyze - none!
;
; CHECK-GCD-MIV-LABEL: 'gcdmiv_delta_ovfl2'
; CHECK-GCD-MIV-NEXT: Src: store i8 0, ptr %gep.0, align 1 --> Dst: store i8 0, ptr %gep.0, align 1
; CHECK-GCD-MIV-NEXT: da analyze - output [* *]!
; CHECK-GCD-MIV-NEXT: Src: store i8 0, ptr %gep.0, align 1 --> Dst: store i8 0, ptr %gep.1, align 1
; CHECK-GCD-MIV-NEXT: da analyze - output [* <>]!
; CHECK-GCD-MIV-NEXT: Src: store i8 0, ptr %gep.1, align 1 --> Dst: store i8 0, ptr %gep.1, align 1
; CHECK-GCD-MIV-NEXT: da analyze - output [* *]!
;
entry:
br label %loop.i.header

loop.i.header:
%i = phi i64 [ 0, %entry ], [ %i.inc, %loop.i.latch ]
%c.i.0 = phi i64 [ 0, %entry ], [ %c.i.0.next, %loop.i.latch ]
%c.i.1 = phi i64 [ -1, %entry ], [ %c.i.1.next, %loop.i.latch ]
br label %loop.j.header

loop.j.header:
%j = phi i64 [ 0, %loop.i.header ], [ %j.inc, %loop.j.latch ]
%offset.0 = phi i64 [ %c.i.0, %loop.i.header ], [ %offset.0.next, %loop.j.latch ]
%offset.1 = phi i64 [ %c.i.1, %loop.i.header ], [ %offset.1.next, %loop.j.latch ]
%cond.0 = icmp eq i64 %offset.0, -5
br i1 %cond.0, label %if.then.0, label %loop.j.middle

if.then.0:
%gep.0 = getelementptr i8, ptr %A, i64 %offset.0
store i8 0, ptr %gep.0
br label %loop.j.middle

loop.j.middle:
%cond.1 = icmp eq i64 %offset.1, -5
br i1 %cond.1, label %if.then.1, label %loop.j.latch

if.then.1:
%gep.1 = getelementptr i8, ptr %A, i64 %offset.1
store i8 0, ptr %gep.1
br label %loop.j.latch

loop.j.latch:
%j.inc = add i64 %j, 1
%offset.0.next = add nsw i64 %offset.0, -9223372036854775805
%offset.1.next = add nsw i64 %offset.1, 9223372036854775796
%ec.j = icmp eq i64 %j, 2
br i1 %ec.j, label %loop.i.latch, label %loop.j.header

loop.i.latch:
%i.inc = add i64 %i, 1
%c.i.0.next = add nsw i64 %c.i.0, 5
%c.i.1.next = add nsw i64 %c.i.1, -5
%ec.i = icmp eq i64 %i.inc, 1844674407370955161
br i1 %ec.i, label %exit, label %loop.i.header

exit:
ret void

}
;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
; CHECK: {{.*}}