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48fcc07856
ScalarEvolution currently lowers a subtraction recurrence to an add recurrence with the same no-wrap flags as the subtraction. This is incorrect because `sub nsw X, Y` is not the same as `add nsw X, -Y` and `sub nuw X, Y` is not the same as `add nuw X, -Y`. This patch fixes the issue, and adds two test cases demonstrating the bug. Differential Revision: http://reviews.llvm.org/D7081 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226755 91177308-0d34-0410-b5e6-96231b3b80d8
42 lines
939 B
LLVM
42 lines
939 B
LLVM
; RUN: opt -S -indvars < %s | FileCheck %s
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; Check that SCEV does not assume sub nuw X Y == add nuw X, -Y
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define void @f(i32* %loc) {
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; CHECK-LABEL: @f
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entry:
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br label %loop
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loop:
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%idx = phi i32 [ 6, %entry ], [ %idx.dec, %loop ]
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store i32 %idx, i32* %loc
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%idx.dec = sub nuw i32 %idx, 1
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%cond = icmp uge i32 %idx.dec, 5
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br i1 %cond, label %loop, label %exit
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; CHECK-NOT: br i1 true, label %loop, label %exit
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exit:
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ret void
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}
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declare void @use_i1(i1)
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; Check that SCEV does not assume sub nsw X Y == add nsw X, -Y
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define void @g(i32 %lim) {
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; CHECK-LABEL: @g
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entry:
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br label %loop
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loop:
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%idx = phi i32 [ -1, %entry ], [ %idx.dec, %loop ]
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%t = icmp sgt i32 %idx, 0
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; CHECK-NOT: call void @use_i1(i1 false)
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; CHECK: call void @use_i1(i1 %t)
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call void @use_i1(i1 %t)
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%idx.dec = sub nsw i32 %idx, -2147483648
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%cond = icmp eq i32 %idx.dec, %lim
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br i1 %cond, label %loop, label %exit
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exit:
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ret void
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}
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