mirror of
https://github.com/c64scene-ar/llvm-6502.git
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a5a3e2d58a
Summary: Before this change ImplicitNullChecks would only pick loads of the form: ``` test Reg, Reg jz elsewhere fallthrough: movl 32(Reg), Reg2 ``` but not (say) ``` test Reg, Reg jz elsewhere fallthrough: inc Reg3 movl 32(Reg), Reg2 ``` This change teaches ImplicitNullChecks to look through "unrelated" instructions like `inc Reg3` when searching for a load instruction to convert to a trapping load. Reviewers: atrick, JosephTremoulet, reames Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D11044 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241850 91177308-0d34-0410-b5e6-96231b3b80d8
97 lines
2.2 KiB
LLVM
97 lines
2.2 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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define i32 @imp_null_check_no_hoist_over_acquire_load(i32* %x, i32* %y) {
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; We cannot hoist %t1 over %t0 since %t0 is an acquire load
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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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%t0 = load atomic i32, i32* %y acquire, align 4
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%t1 = load i32, i32* %x
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%p = add i32 %t0, %t1
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ret i32 %p
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}
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define i32 @imp_null_check_add_result(i32* %x, i32* %y) {
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; This will codegen to:
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;
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; movl (%rsi), %eax
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; addl (%rdi), %eax
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;
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; The load instruction we wish to hoist is the addl, but there is a
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; write-after-write hazard preventing that from happening. We could
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; get fancy here and exploit the commutativity of addition, but right
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; now -implicit-null-checks isn't that smart.
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;
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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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%t0 = load i32, i32* %y
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%t1 = load i32, i32* %x
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%p = add i32 %t0, %t1
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ret i32 %p
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}
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!0 = !{}
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