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[CGP] Fix handling of null pointer values in optimizeMemoryInst

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The current way that trivial addressing modes are detected incorrectly thinks
that null pointers are non-trivial, leading to an infinite loop where we keep
duplicating the same select. Fix this by aware of null when deciding if an
addressing mode is trivial.

Differential Revision: https://reviews.llvm.org/D40447

llvm-svn: 319019
This commit is contained in:
John Brawn 2017-11-27 11:29:15 +00:00
parent f3c0aec971
commit 4b476488ba
2 changed files with 59 additions and 9 deletions
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16
llvm/lib/CodeGen/CodeGenPrepare.cpp
View File

@ -2080,16 +2080,14 @@ struct ExtAddrMode : public TargetLowering::AddrMode {
return static_cast<FieldName>(Result);
}
// AddrModes with a baseReg or gv where the reg/gv is
// the only populated field are trivial.
// An AddrMode is trivial if it involves no calculation i.e. it is just a base
// with no offset.
bool isTrivial() {
if (BaseGV && !BaseOffs && !Scale && !BaseReg)
return true;
if (!BaseGV && !BaseOffs && !Scale && BaseReg)
return true;
return false;
// An AddrMode is (BaseGV + BaseReg + BaseOffs + ScaleReg * Scale) so it is
// trivial if at most one of these terms is nonzero, except that BaseGV and
// BaseReg both being zero actually means a null pointer value, which we
// consider to be 'non-zero' here.
return !BaseOffs && !Scale && !(BaseGV && BaseReg);
}
Value *GetFieldAsValue(FieldName Field, Type *IntPtrTy) {

52
llvm/test/Transforms/CodeGenPrepare/ARM/sink-addrmode.ll
View File

@ -366,3 +366,55 @@ entey:
store i32 %value, i32* %select, align 4
ret void
}
; Same for a select between a value and global variable
; CHECK-LABEL: @test_select_trivial_ptr_gv
; CHECK: select i1 %cmp, i32* %ptr, i32* @gv2
define void @test_select_trivial_ptr_gv(i32* %ptr, i32 %value) {
entry:
%cmp = icmp sgt i32 %value, 0
%select = select i1 %cmp, i32* %ptr, i32* @gv2
store i32 %value, i32* %select, align 4
ret void
}
; Same for a select between a global variable and null, though the test needs to
; be a little more complicated to avoid dereferencing a potential null pointer
; CHECK-LABEL: @test_select_trivial_gv_null
; CHECK: select i1 %cmp.i, i32* @gv1, i32* null
define void @test_select_trivial_gv_null(){
entry:
%gv1_val = load i32, i32* @gv1, align 4
%cmp.i = icmp eq i32 %gv1_val, 0
%spec.select.i = select i1 %cmp.i, i32* @gv1, i32* null
br i1 %cmp.i, label %if.then, label %if.end
if.then:
%val = load i32, i32* %spec.select.i, align 4
%inc = add nsw i32 %val, 1
store i32 %inc, i32* %spec.select.i, align 4
br label %if.end
if.end:
ret void
}
; Same for a select between a value and null
; CHECK-LABEL: @test_select_trivial_ptr_null
; CHECK: select i1 %cmp.i, i32* %ptr, i32* null
define void @test_select_trivial_ptr_null(i32* %ptr){
entry:
%gv1_val = load i32, i32* %ptr, align 4
%cmp.i = icmp eq i32 %gv1_val, 0
%spec.select.i = select i1 %cmp.i, i32* %ptr, i32* null
br i1 %cmp.i, label %if.then, label %if.end
if.then:
%val = load i32, i32* %spec.select.i, align 4
%inc = add nsw i32 %val, 1
store i32 %inc, i32* %spec.select.i, align 4
br label %if.end
if.end:
ret void
}