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https://github.com/c64scene-ar/llvm-6502.git
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7e32aa1015
System memory allocation functions, which are identified at the IR level by the noalias attribute on the return value, must return a pointer into a memory region disjoint from any other memory accessible to the caller. We can use this property to simplify pointer comparisons between allocated memory and local stack addresses and the addresses of global variables. Neither the stack nor global variables can overlap with the region used by the memory allocator. Fixes PR21556. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223093 91177308-0d34-0410-b5e6-96231b3b80d8
109 lines
3.1 KiB
LLVM
109 lines
3.1 KiB
LLVM
; RUN: opt -instsimplify -S < %s | FileCheck %s
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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@g1 = global i32 0, align 4
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; Make sure we can simplify away a pointer comparison between
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; dynamically-allocated memory and a local stack allocation.
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; void p()
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; {
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; int *mData;
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; int mStackData[10];
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; mData = new int[12];
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; if (mData != mStackData) {
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; delete[] mData;
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; }
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; }
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define void @_Z2p1v() #0 {
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%mStackData = alloca [10 x i32], align 16
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%1 = bitcast [10 x i32]* %mStackData to i8*
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%2 = tail call noalias i8* @_Znam(i64 48) #4
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%3 = bitcast i8* %2 to i32*
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%4 = getelementptr inbounds [10 x i32]* %mStackData, i64 0, i64 0
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%5 = icmp eq i32* %3, %4
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br i1 %5, label %7, label %6
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; CHECK-LABEL: @_Z2p1v
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; CHECK-NOT: icmp
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; CHECK: ret void
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; <label>:6 ; preds = %0
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call void @_ZdaPv(i8* %2) #5
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br label %7
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; <label>:7 ; preds = %0, %6
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ret void
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}
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; Also check a more-complicated case with multiple underlying objects.
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define void @_Z2p2bb(i1 zeroext %b1, i1 zeroext %b2) #0 {
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%mStackData = alloca [10 x i32], align 16
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%1 = bitcast [10 x i32]* %mStackData to i8*
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%2 = getelementptr inbounds [10 x i32]* %mStackData, i64 0, i64 0
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%3 = select i1 %b1, i32* %2, i32* @g1
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%4 = tail call noalias i8* @_Znam(i64 48) #4
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%5 = tail call noalias i8* @_Znam(i64 48) #4
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%.v = select i1 %b2, i8* %4, i8* %5
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%6 = bitcast i8* %.v to i32*
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%7 = icmp eq i32* %6, %3
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br i1 %7, label %9, label %8
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; CHECK-LABEL: @_Z2p2bb
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; CHECK-NOT: icmp
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; CHECK: ret void
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; <label>:8 ; preds = %0
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call void @_ZdaPv(i8* %4) #5
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call void @_ZdaPv(i8* %5) #5
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br label %9
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; <label>:9 ; preds = %0, %8
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ret void
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}
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; Here's another case involving multiple underlying objects, but this time we
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; must keep the comparison (it might involve a regular pointer-typed function
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; argument).
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define void @_Z4nopebbPi(i1 zeroext %b1, i1 zeroext %b2, i32* readnone %q) #0 {
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%mStackData = alloca [10 x i32], align 16
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%1 = bitcast [10 x i32]* %mStackData to i8*
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%2 = getelementptr inbounds [10 x i32]* %mStackData, i64 0, i64 0
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%3 = select i1 %b1, i32* %2, i32* %q
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%4 = tail call noalias i8* @_Znam(i64 48) #4
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%5 = tail call noalias i8* @_Znam(i64 48) #4
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%.v = select i1 %b2, i8* %4, i8* %5
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%6 = bitcast i8* %.v to i32*
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%7 = icmp eq i32* %6, %3
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br i1 %7, label %9, label %8
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; CHECK-LABEL: @_Z4nopebbPi
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; CHECK: icmp
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; CHECK: ret void
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; <label>:8 ; preds = %0
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call void @_ZdaPv(i8* %4) #5
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call void @_ZdaPv(i8* %5) #5
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br label %9
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; <label>:9 ; preds = %0, %8
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ret void
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}
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; Function Attrs: nobuiltin
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declare noalias i8* @_Znam(i64) #2
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; Function Attrs: nobuiltin nounwind
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declare void @_ZdaPv(i8*) #3
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attributes #0 = { uwtable }
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attributes #1 = { nounwind }
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attributes #2 = { nobuiltin }
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attributes #3 = { nobuiltin nounwind }
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attributes #4 = { builtin }
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attributes #5 = { builtin nounwind }
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