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152dec707a
Summary: When performing constant propagation for call instructions we have historically replaced all uses of the return from a call, but not removed the call itself. This is required for correctness if the calls have side effects, however the compiler should be able to safely remove calls that don't have side effects. This allows the compiler to completely fold away calls to functions that have no side effects if the inputs are constant and the output can be determined at compile time. Reviewers: davide, sanjoy, bruno, dberlin Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D38856 llvm-svn: 322125
34 lines
691 B
LLVM
34 lines
691 B
LLVM
; RUN: opt < %s -S -ipsccp | FileCheck %s
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; PR5596
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; IPSCCP should propagate the 0 argument, eliminate the switch, and propagate
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; the result.
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; CHECK: define i32 @main() #0 {
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; CHECK-NEXT: entry:
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; CHECK-NEXT: %call2 = tail call i32 @wwrite(i64 0) [[NUW:#[0-9]+]]
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; CHECK-NEXT: ret i32 123
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define i32 @main() noreturn nounwind {
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entry:
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%call2 = tail call i32 @wwrite(i64 0) nounwind
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ret i32 %call2
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}
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define internal i32 @wwrite(i64 %i) nounwind {
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entry:
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switch i64 %i, label %sw.default [
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i64 3, label %return
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i64 10, label %return
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]
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sw.default:
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ret i32 123
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return:
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ret i32 0
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}
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; CHECK: attributes #0 = { noreturn nounwind }
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; CHECK: attributes #1 = { nounwind }
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