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https://github.com/c64scene-ar/llvm-6502.git
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908d4514f6
by my refactoring of this code. The method isSafeToLoadUnconditionally assumes that the load will proceed with the preferred type alignment. Given that, it has to ensure that the alloca or global is at least that aligned. It has always done this historically when a datalayout is present, but has never checked it when the datalayout is absent. When I refactored the code in r220156, I exposed this path when datalayout was present and that turned the latent bug into a patent bug. This fixes the issue by just removing the special case which allows folding things without datalayout. This isn't worth the complexity of trying to tease apart when it is or isn't safe without actually knowing the preferred alignment. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220161 91177308-0d34-0410-b5e6-96231b3b80d8
125 lines
3.7 KiB
LLVM
125 lines
3.7 KiB
LLVM
; RUN: opt < %s -tailcallelim -S | FileCheck %s
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; PR4323
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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; Several cases where tail call elimination should move the load above the call,
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; then eliminate the tail recursion.
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@global = external global i32 ; <i32*> [#uses=1]
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@extern_weak_global = extern_weak global i32 ; <i32*> [#uses=1]
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; This load can be moved above the call because the function won't write to it
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; and the call has no side effects.
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define fastcc i32 @raise_load_1(i32* %a_arg, i32 %a_len_arg, i32 %start_arg) nounwind readonly {
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; CHECK-LABEL: @raise_load_1(
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; CHECK-NOT: call
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; CHECK: load i32*
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; CHECK-NOT: call
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; CHECK: }
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entry:
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%tmp2 = icmp sge i32 %start_arg, %a_len_arg ; <i1> [#uses=1]
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br i1 %tmp2, label %if, label %else
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if: ; preds = %entry
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ret i32 0
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else: ; preds = %entry
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%tmp7 = add i32 %start_arg, 1 ; <i32> [#uses=1]
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%tmp8 = call fastcc i32 @raise_load_1(i32* %a_arg, i32 %a_len_arg, i32 %tmp7) ; <i32> [#uses=1]
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%tmp9 = load i32* %a_arg ; <i32> [#uses=1]
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%tmp10 = add i32 %tmp9, %tmp8 ; <i32> [#uses=1]
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ret i32 %tmp10
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}
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; This load can be moved above the call because the function won't write to it
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; and the load provably can't trap.
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define fastcc i32 @raise_load_2(i32* %a_arg, i32 %a_len_arg, i32 %start_arg) readonly {
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; CHECK-LABEL: @raise_load_2(
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; CHECK-NOT: call
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; CHECK: load i32*
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; CHECK-NOT: call
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; CHECK: }
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entry:
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%tmp2 = icmp sge i32 %start_arg, %a_len_arg ; <i1> [#uses=1]
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br i1 %tmp2, label %if, label %else
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if: ; preds = %entry
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ret i32 0
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else: ; preds = %entry
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%nullcheck = icmp eq i32* %a_arg, null ; <i1> [#uses=1]
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br i1 %nullcheck, label %unwind, label %recurse
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unwind: ; preds = %else
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unreachable
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recurse: ; preds = %else
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%tmp7 = add i32 %start_arg, 1 ; <i32> [#uses=1]
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%tmp8 = call fastcc i32 @raise_load_2(i32* %a_arg, i32 %a_len_arg, i32 %tmp7) ; <i32> [#uses=1]
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%tmp9 = load i32* @global ; <i32> [#uses=1]
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%tmp10 = add i32 %tmp9, %tmp8 ; <i32> [#uses=1]
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ret i32 %tmp10
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}
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; This load can be safely moved above the call (even though it's from an
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; extern_weak global) because the call has no side effects.
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define fastcc i32 @raise_load_3(i32* %a_arg, i32 %a_len_arg, i32 %start_arg) nounwind readonly {
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; CHECK-LABEL: @raise_load_3(
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; CHECK-NOT: call
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; CHECK: load i32*
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; CHECK-NOT: call
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; CHECK: }
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entry:
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%tmp2 = icmp sge i32 %start_arg, %a_len_arg ; <i1> [#uses=1]
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br i1 %tmp2, label %if, label %else
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if: ; preds = %entry
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ret i32 0
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else: ; preds = %entry
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%tmp7 = add i32 %start_arg, 1 ; <i32> [#uses=1]
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%tmp8 = call fastcc i32 @raise_load_3(i32* %a_arg, i32 %a_len_arg, i32 %tmp7) ; <i32> [#uses=1]
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%tmp9 = load i32* @extern_weak_global ; <i32> [#uses=1]
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%tmp10 = add i32 %tmp9, %tmp8 ; <i32> [#uses=1]
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ret i32 %tmp10
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}
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; The second load can be safely moved above the call even though it's from an
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; unknown pointer (which normally means it might trap) because the first load
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; proves it doesn't trap.
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define fastcc i32 @raise_load_4(i32* %a_arg, i32 %a_len_arg, i32 %start_arg) readonly {
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; CHECK-LABEL: @raise_load_4(
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; CHECK-NOT: call
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; CHECK: load i32*
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; CHECK-NEXT: load i32*
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; CHECK-NOT: call
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; CHECK: }
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entry:
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%tmp2 = icmp sge i32 %start_arg, %a_len_arg ; <i1> [#uses=1]
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br i1 %tmp2, label %if, label %else
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if: ; preds = %entry
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ret i32 0
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else: ; preds = %entry
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%nullcheck = icmp eq i32* %a_arg, null ; <i1> [#uses=1]
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br i1 %nullcheck, label %unwind, label %recurse
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unwind: ; preds = %else
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unreachable
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recurse: ; preds = %else
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%tmp7 = add i32 %start_arg, 1 ; <i32> [#uses=1]
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%first = load i32* %a_arg ; <i32> [#uses=1]
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%tmp8 = call fastcc i32 @raise_load_4(i32* %a_arg, i32 %first, i32 %tmp7) ; <i32> [#uses=1]
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%second = load i32* %a_arg ; <i32> [#uses=1]
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%tmp10 = add i32 %second, %tmp8 ; <i32> [#uses=1]
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ret i32 %tmp10
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}
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