9c41a93e24
Summary: This change introduces a !make.implicit metadata that allows the frontend to pre-select the set of explicit null checks that will be considered for transformation into implicit null checks. The reason for not using profiling data instead of !make.implicit is explained in the change to `FaultMaps.rst`. Reviewers: atrick, reames, pgavlin, JosephTremoulet Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D10824 llvm-svn: 241116
55 lines
1.3 KiB
LLVM
55 lines
1.3 KiB
LLVM
; RUN: llc -mtriple=x86_64-apple-macosx -O3 -debug-only=faultmaps -enable-implicit-null-checks < %s 2>&1 | FileCheck %s
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; REQUIRES: asserts
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; List cases where we should *not* be emitting implicit null checks.
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; CHECK-NOT: Fault Map Output
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define i32 @imp_null_check_load(i32* %x, i32* %y) {
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entry:
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%c = icmp eq i32* %x, null
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; It isn't legal to move the load from %x from "not_null" to here --
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; the store to %y could be aliasing it.
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br i1 %c, label %is_null, label %not_null, !make.implicit !0
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is_null:
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ret i32 42
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not_null:
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store i32 0, i32* %y
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%t = load i32, i32* %x
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ret i32 %t
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}
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define i32 @imp_null_check_gep_load(i32* %x) {
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entry:
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%c = icmp eq i32* %x, null
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br i1 %c, label %is_null, label %not_null, !make.implicit !0
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is_null:
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ret i32 42
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not_null:
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; null + 5000 * sizeof(i32) lies outside the null page and hence the
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; load to %t cannot be assumed to be reliably faulting.
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%x.gep = getelementptr i32, i32* %x, i32 5000
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%t = load i32, i32* %x.gep
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ret i32 %t
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}
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define i32 @imp_null_check_load_no_md(i32* %x) {
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; This is fine, except it is missing the !make.implicit metadata.
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entry:
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%c = icmp eq i32* %x, null
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br i1 %c, label %is_null, label %not_null
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is_null:
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ret i32 42
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not_null:
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%t = load i32, i32* %x
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ret i32 %t
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}
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!0 = !{}
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