9ac7021a25
IRCE for unsigned latch conditions was temporarily disabled by rL314881. The motivating example contained an unsigned latch condition and a signed range check. One of the safe iteration ranges was `[1, SINT_MAX + 1]`. Its right border was incorrectly interpreted as a negative value in `IntersectRange` function, this lead to a miscompile under which we deleted a range check without inserting a postloop where it was needed. This patch brings back IRCE for unsigned latch conditions. Now we treat range intersection more carefully. If the latch condition was unsigned, we only try to consider a range check for deletion if: 1. The range check is also unsigned, or 2. Safe iteration range of the range check lies within `[0, SINT_MAX]`. The same is done for signed latch. Values from `[0, SINT_MAX]` are unambiguous, these values are non-negative under any interpretation, and all values of a range intersected with such range are also non-negative. We also use signed/unsigned min/max functions for range intersection depending on type of the latch condition. Differential Revision: https://reviews.llvm.org/D38581 llvm-svn: 316552
69 lines
2.3 KiB
LLVM
69 lines
2.3 KiB
LLVM
; RUN: opt -verify-loop-info -irce-print-changed-loops -irce -S
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; Make sure that IRCE doesn't apply in case of empty ranges.
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; (i + 30 < 40) if i in [-30, 10).
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; Intersected with iteration space, it is [0, 10).
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; (i - 60 < 40) if i in [60 , 100).
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; The intersection with safe iteration space is the empty range [60, 10).
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; It is better to eliminate one range check than attempt to eliminate both given
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; that we will never go to the main loop in the latter case and basically
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; only duplicate code with no benefits.
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define void @test_01(i32* %arr, i32* %a_len_ptr) #0 {
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; CHECK-LABEL: test_01(
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; CHECK-NOT: preloop
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; CHECK: entry:
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; CHECK-NEXT: br i1 true, label %loop.preheader, label %main.pseudo.exit
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; CHECK: in.bounds.1:
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; CHECK-NEXT: %addr = getelementptr i32, i32* %arr, i32 %idx
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; CHECK-NEXT: store i32 0, i32* %addr
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; CHECK-NEXT: %off1 = add i32 %idx, 30
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; CHECK-NEXT: %c2 = icmp slt i32 %off1, 40
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; CHECK-NEXT: br i1 true, label %in.bounds.2, label %exit.loopexit2
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; CHECK: in.bounds.2:
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; CHECK-NEXT: %off2 = add i32 %idx, -60
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; CHECK-NEXT: %c3 = icmp slt i32 %off2, 40
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; CHECK-NEXT: br i1 %c3, label %in.bounds.3, label %exit.loopexit2
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; CHECK: in.bounds.3:
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; CHECK-NEXT: %next = icmp ult i32 %idx.next, 100
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; CHECK-NEXT: [[COND1:%[^ ]+]] = icmp ult i32 %idx.next, 10
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; CHECK-NEXT: br i1 [[COND1]], label %loop, label %main.exit.selector
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; CHECK: main.exit.selector:
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; CHECK-NEXT: %idx.next.lcssa = phi i32 [ %idx.next, %in.bounds.3 ]
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; CHECK-NEXT: [[COND2:%[^ ]+]] = icmp ult i32 %idx.next.lcssa, 100
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; CHECK-NEXT: br i1 [[COND2]], label %main.pseudo.exit, label %exit
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; CHECK: postloop:
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entry:
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br label %loop
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loop:
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%idx = phi i32 [ 0, %entry ], [ %idx.next, %in.bounds.3 ]
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%idx.next = add nsw nuw i32 %idx, 1
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%c1 = icmp slt i32 %idx, 20
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br i1 %c1, label %in.bounds.1, label %out.of.bounds
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in.bounds.1:
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%addr = getelementptr i32, i32* %arr, i32 %idx
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store i32 0, i32* %addr
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%off1 = add i32 %idx, 30
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%c2 = icmp slt i32 %off1, 40
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br i1 %c2, label %in.bounds.2, label %exit
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in.bounds.2:
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%off2 = add i32 %idx, -60
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%c3 = icmp slt i32 %off2, 40
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br i1 %c3, label %in.bounds.3, label %exit
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in.bounds.3:
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%next = icmp ult i32 %idx.next, 100
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br i1 %next, label %loop, label %exit
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out.of.bounds:
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ret void
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exit:
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ret void
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}
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