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Some instructions from the original loop, when vectorized, can become trivially dead. This happens because of the way we structure the new loop. For example, we create new induction variables and induction variable "steps" in the new loop. Thus, when we go to vectorize the original induction variable update, it may no longer be needed due to the instructions we've already created. This patch prevents us from creating these redundant instructions. This reduces code size before simplification and allows greater flexibility in code generation since we have fewer unnecessary instruction uses. Differential Revision: https://reviews.llvm.org/D25631 llvm-svn: 284631
43 lines
1.6 KiB
LLVM
43 lines
1.6 KiB
LLVM
; RUN: opt < %s -force-vector-width=2 -force-vector-interleave=2 -loop-vectorize -S | FileCheck %s
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target datalayout = "e-m:e-i64:64-i128:128-n32:64-S128"
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; CHECK-LABEL: @dead_instructions_01
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;
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; This test ensures that we don't generate trivially dead instructions prior to
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; instruction simplification. We don't need to generate instructions
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; corresponding to the original induction variable update or branch condition,
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; since we rewrite the loop structure.
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;
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; CHECK: vector.body:
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; CHECK: %index = phi i64 [ 0, %vector.ph ], [ %index.next, %vector.body ]
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; CHECK: %[[I0:.+]] = add i64 %index, 0
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; CHECK: %[[I2:.+]] = add i64 %index, 2
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; CHECK: getelementptr inbounds i64, i64* %a, i64 %[[I0]]
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; CHECK: getelementptr inbounds i64, i64* %a, i64 %[[I2]]
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; CHECK-NOT: add nuw nsw i64 %[[I0]], 1
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; CHECK-NOT: add nuw nsw i64 %[[I2]], 1
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; CHECK-NOT: icmp slt i64 {{.*}}, %n
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; CHECK: %index.next = add i64 %index, 4
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; CHECK: %[[CMP:.+]] = icmp eq i64 %index.next, %n.vec
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; CHECK: br i1 %[[CMP]], label %middle.block, label %vector.body
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;
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define i64 @dead_instructions_01(i64 *%a, i64 %n) {
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entry:
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br label %for.body
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for.body:
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%i = phi i64 [ %i.next, %for.body ], [ 0, %entry ]
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%r = phi i64 [ %tmp2, %for.body ], [ 0, %entry ]
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%tmp0 = getelementptr inbounds i64, i64* %a, i64 %i
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%tmp1 = load i64, i64* %tmp0, align 8
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%tmp2 = add i64 %tmp1, %r
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%i.next = add nuw nsw i64 %i, 1
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%cond = icmp slt i64 %i.next, %n
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br i1 %cond, label %for.body, label %for.end
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for.end:
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%tmp3 = phi i64 [ %tmp2, %for.body ]
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ret i64 %tmp3
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}
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