46 lines
1.7 KiB
LLVM
46 lines
1.7 KiB
LLVM
; RUN: opt < %s -gvn -enable-load-pre -S | FileCheck %s
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; This testcase assumed we'll PRE the load into %for.cond, but we don't actually
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; verify that doing so is safe. If there didn't _happen_ to be a load in
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; %for.end, we would actually be lengthening the execution on some paths, and
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; we were never actually checking that case. Now we actually do perform some
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; conservative checking to make sure we don't make paths longer, but we don't
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; currently get this case, which we got lucky on previously.
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;
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; Now that that faulty assumption is corrected, test that we DON'T incorrectly
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; hoist the load. Doing the right thing for the wrong reasons is still a bug.
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@p = external global i32
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define i32 @f(i32 %n) nounwind {
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entry:
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br label %for.cond
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for.cond: ; preds = %for.inc, %entry
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%i.0 = phi i32 [ 0, %entry ], [ %indvar.next, %for.inc ] ; <i32> [#uses=2]
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%cmp = icmp slt i32 %i.0, %n ; <i1> [#uses=1]
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br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge
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for.cond.for.end_crit_edge: ; preds = %for.cond
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br label %for.end
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; CHECK: for.body:
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; CHECK-NEXT: %tmp3 = load i32* @p
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for.body: ; preds = %for.cond
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%tmp3 = load i32* @p ; <i32> [#uses=1]
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%dec = add i32 %tmp3, -1 ; <i32> [#uses=2]
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store i32 %dec, i32* @p
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%cmp6 = icmp slt i32 %dec, 0 ; <i1> [#uses=1]
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br i1 %cmp6, label %for.body.for.end_crit_edge, label %for.inc
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; CHECK: for.body.for.end_crit_edge:
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for.body.for.end_crit_edge: ; preds = %for.body
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br label %for.end
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for.inc: ; preds = %for.body
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%indvar.next = add i32 %i.0, 1 ; <i32> [#uses=1]
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br label %for.cond
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for.end: ; preds = %for.body.for.end_crit_edge, %for.cond.for.end_crit_edge
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%tmp9 = load i32* @p ; <i32> [#uses=1]
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ret i32 %tmp9
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}
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