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Push isDereferenceableAndAlignedPointer down into isSafeToLoadUnconditionally

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Reviewed By: reames

Differential Revision: http://reviews.llvm.org/D16226


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@258010 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Artur Pilipenko 2016-01-17 12:35:29 +00:00
parent e74c24049c
commit ae316aa098
6 changed files with 78 additions and 17 deletions
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3
lib/Analysis/Loads.cpp
View File

@ -71,6 +71,9 @@ bool llvm::isSafeToLoadUnconditionally(Value *V, unsigned Align,
Align = DL.getABITypeAlignment(V->getType()->getPointerElementType());
assert(isPowerOf2_32(Align));
if (isDereferenceableAndAlignedPointer(V, Align, DL))
return true;
int64_t ByteOffset = 0;
Value *Base = V;
Base = GetPointerBaseWithConstantOffset(V, ByteOffset, DL);

11
lib/Transforms/Scalar/SROA.cpp
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@ -1192,8 +1192,7 @@ static bool isSafePHIToSpeculate(PHINode &PN) {
// If this pointer is always safe to load, or if we can prove that there
// is already a load in the block, then we can move the load to the pred
// block.
if (isDereferenceablePointer(InVal, DL) ||
isSafeToLoadUnconditionally(InVal, MaxAlign, TI))
if (isSafeToLoadUnconditionally(InVal, MaxAlign, TI))
continue;
return false;
@ -1262,8 +1261,6 @@ static bool isSafeSelectToSpeculate(SelectInst &SI) {
Value *TValue = SI.getTrueValue();
Value *FValue = SI.getFalseValue();
const DataLayout &DL = SI.getModule()->getDataLayout();
bool TDerefable = isDereferenceablePointer(TValue, DL);
bool FDerefable = isDereferenceablePointer(FValue, DL);
for (User *U : SI.users()) {
LoadInst *LI = dyn_cast<LoadInst>(U);
@ -1273,11 +1270,9 @@ static bool isSafeSelectToSpeculate(SelectInst &SI) {
// Both operands to the select need to be dereferencable, either
// absolutely (e.g. allocas) or at this point because we can see other
// accesses to it.
if (!TDerefable &&
!isSafeToLoadUnconditionally(TValue, LI->getAlignment(), LI))
if (!isSafeToLoadUnconditionally(TValue, LI->getAlignment(), LI))
return false;
if (!FDerefable &&
!isSafeToLoadUnconditionally(FValue, LI->getAlignment(), LI))
if (!isSafeToLoadUnconditionally(FValue, LI->getAlignment(), LI))
return false;
}

11
lib/Transforms/Scalar/ScalarReplAggregates.cpp
View File

@ -1141,8 +1141,6 @@ public:
/// the select can be loaded unconditionally.
static bool isSafeSelectToSpeculate(SelectInst *SI) {
const DataLayout &DL = SI->getModule()->getDataLayout();
bool TDerefable = isDereferenceablePointer(SI->getTrueValue(), DL);
bool FDerefable = isDereferenceablePointer(SI->getFalseValue(), DL);
for (User *U : SI->users()) {
LoadInst *LI = dyn_cast<LoadInst>(U);
@ -1150,12 +1148,10 @@ static bool isSafeSelectToSpeculate(SelectInst *SI) {
// Both operands to the select need to be dereferencable, either absolutely
// (e.g. allocas) or at this point because we can see other accesses to it.
if (!TDerefable &&
!isSafeToLoadUnconditionally(SI->getTrueValue(), LI->getAlignment(),
if (!isSafeToLoadUnconditionally(SI->getTrueValue(), LI->getAlignment(),
LI))
return false;
if (!FDerefable &&
!isSafeToLoadUnconditionally(SI->getFalseValue(), LI->getAlignment(),
if (!isSafeToLoadUnconditionally(SI->getFalseValue(), LI->getAlignment(),
LI))
return false;
}
@ -1229,8 +1225,7 @@ static bool isSafePHIToSpeculate(PHINode *PN) {
// If this pointer is always safe to load, or if we can prove that there is
// already a load in the block, then we can move the load to the pred block.
if (isDereferenceablePointer(InVal, DL) ||
isSafeToLoadUnconditionally(InVal, MaxAlign, Pred->getTerminator()))
if (isSafeToLoadUnconditionally(InVal, MaxAlign, Pred->getTerminator()))
continue;
return false;

27
test/Transforms/InstCombine/select.ll
View File

@ -1296,6 +1296,20 @@ entry:
ret i32 %v
}
define i32 @test78_deref(i1 %flag, i32* dereferenceable(4) %x, i32* dereferenceable(4) %y, i32* %z) {
; Test that we can speculate the loads around the select even when we can't
; fold the load completely away.
; CHECK-LABEL: @test78_deref(
; CHECK: %[[V1:.*]] = load i32, i32* %x
; CHECK-NEXT: %[[V2:.*]] = load i32, i32* %y
; CHECK-NEXT: %[[S:.*]] = select i1 %flag, i32 %[[V1]], i32 %[[V2]]
; CHECK-NEXT: ret i32 %[[S]]
entry:
%p = select i1 %flag, i32* %x, i32* %y
%v = load i32, i32* %p
ret i32 %v
}
define i32 @test78_neg(i1 %flag, i32* %x, i32* %y, i32* %z) {
; The same as @test78 but we can't speculate the load because it can trap
; if under-aligned.
@ -1313,6 +1327,19 @@ entry:
ret i32 %v
}
define i32 @test78_deref_neg(i1 %flag, i32* dereferenceable(2) %x, i32* dereferenceable(4) %y, i32* %z) {
; The same as @test78_deref but we can't speculate the load because
; one of the arguments is not sufficiently dereferenceable.
; CHECK-LABEL: @test78_deref_neg(
; CHECK: %p = select i1 %flag, i32* %x, i32* %y
; CHECK-NEXT: %v = load i32, i32* %p
; CHECK-NEXT: ret i32 %v
entry:
%p = select i1 %flag, i32* %x, i32* %y
%v = load i32, i32* %p
ret i32 %v
}
define float @test79(i1 %flag, float* %x, i32* %y, i32* %z) {
; Test that we can speculate the loads around the select even when we can't
; fold the load completely away.

20
test/Transforms/TailCallElim/dont_reorder_load.ll
View File

@ -1,4 +1,4 @@
; RUN: opt < %s -tailcallelim -S | grep call | count 3
; RUN: opt < %s -tailcallelim -S | grep call | count 4
; PR4323
; Several cases where tail call elimination should not move the load above the
@ -62,3 +62,21 @@ else: ; preds = %entry
%tmp10 = add i32 %tmp9, %tmp8 ; <i32> [#uses=1]
ret i32 %tmp10
}
; This load can NOT be moved above the call because the a_arg is not
; sufficiently dereferenceable.
define fastcc i32 @no_tailrecelim_4(i32* dereferenceable(2) %a_arg, i32 %a_len_arg, i32 %start_arg) readonly {
entry:
%tmp2 = icmp sge i32 %start_arg, %a_len_arg ; <i1> [#uses=1]
br i1 %tmp2, label %if, label %else
if: ; preds = %entry
ret i32 0
else: ; preds = %entry
%tmp7 = add i32 %start_arg, 1 ; <i32> [#uses=1]
%tmp8 = call fastcc i32 @no_tailrecelim_4(i32* %a_arg, i32 %a_len_arg, i32 %tmp7) ; <i32> [#uses=1]
%tmp9 = load i32, i32* %a_arg ; <i32> [#uses=1]
%tmp10 = add i32 %tmp9, %tmp8 ; <i32> [#uses=1]
ret i32 %tmp10
}

23
test/Transforms/TailCallElim/reorder_load.ll
View File

@ -122,3 +122,26 @@ recurse: ; preds = %else
%tmp10 = add i32 %second, %tmp8 ; <i32> [#uses=1]
ret i32 %tmp10
}
; This load can be moved above the call because the function won't write to it
; and the a_arg is dereferenceable.
define fastcc i32 @raise_load_5(i32* dereferenceable(4) %a_arg, i32 %a_len_arg, i32 %start_arg) readonly {
; CHECK-LABEL: @raise_load_5(
; CHECK-NOT: call
; CHECK: load i32, i32*
; CHECK-NOT: call
; CHECK: }
entry:
%tmp2 = icmp sge i32 %start_arg, %a_len_arg ; <i1> [#uses=1]
br i1 %tmp2, label %if, label %else
if: ; preds = %entry
ret i32 0
else: ; preds = %entry
%tmp7 = add i32 %start_arg, 1 ; <i32> [#uses=1]
%tmp8 = call fastcc i32 @raise_load_5(i32* %a_arg, i32 %a_len_arg, i32 %tmp7) ; <i32> [#uses=1]
%tmp9 = load i32, i32* %a_arg ; <i32> [#uses=1]
%tmp10 = add i32 %tmp9, %tmp8 ; <i32> [#uses=1]
ret i32 %tmp10
}