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https://github.com/c64scene-ar/llvm-6502.git
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8e7e3650af
Summary: This at least saves compile time. I also encountered a case where ephemeral values affect whether other variables are promoted, causing performance issues. It may be a bug in LSR, but I didn't manage to reduce it yet. Anyhow, I believe it's in general not worth considering ephemeral values in LSR. Reviewers: atrick, hfinkel Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D11115 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242011 91177308-0d34-0410-b5e6-96231b3b80d8
42 lines
898 B
LLVM
42 lines
898 B
LLVM
; RUN: opt < %s -loop-reduce -S | FileCheck %s
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target datalayout = "e-i64:64-v16:16-v32:32-n16:32:64"
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; for (int i = 0; i < n; ++i) {
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; use(i * 5 + 3);
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; // i * a + b is ephemeral and shouldn't be promoted by LSR
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; __builtin_assume(i * a + b >= 0);
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; }
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define void @ephemeral(i32 %a, i32 %b, i32 %n) {
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; CHECK-LABEL: @ephemeral(
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entry:
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br label %loop
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loop:
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%i = phi i32 [ 0, %entry ], [ %inc, %loop ]
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; Only i and i * 5 + 3 should be indvars, not i * a + b.
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; CHECK: phi i32
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; CHECK: phi i32
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; CHECK-NOT: phi i32
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%inc = add nsw i32 %i, 1
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%exitcond = icmp eq i32 %inc, %n
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%0 = mul nsw i32 %i, 5
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%1 = add nsw i32 %0, 3
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call void @use(i32 %1)
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%2 = mul nsw i32 %i, %a
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%3 = add nsw i32 %2, %b
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%4 = icmp sgt i32 %3, -1
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call void @llvm.assume(i1 %4)
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br i1 %exitcond, label %exit, label %loop
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exit:
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ret void
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}
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declare void @use(i32)
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declare void @llvm.assume(i1)
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