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[InstCombine] reverse bitcast + bitwise-logic canonicalization (PR33138)

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There are 2 parts to this patch made simultaneously to avoid a regression.

We're reversing the canonicalization that moves bitwise vector ops before bitcasts. 
We're moving bitwise vector ops *after* bitcasts instead. That's the 1st and 3rd hunks 
of the patch. The motivation is that there's only one fold that currently depends on 
the existing canonicalization (see next), but there are many folds that would 
automatically benefit from the new canonicalization. 
PR33138 ( https://bugs.llvm.org/show_bug.cgi?id=33138 ) shows why/how we have these 
patterns in IR.

There's an or(and,andn) pattern that requires an adjustment in order to continue matching
to 'select' because the bitcast changes position. This match is unfortunately complicated 
because it requires 4 logic ops with optional bitcast and sext ops.

Test diffs:

  1. The bitcast.ll and bitcast-bigendian.ll changes show the most basic difference - 
     bitcast comes before logic.
  2. There are also tests with no diffs in bitcast.ll that verify that we're still doing 
     folds that were enabled by the previous canonicalization.
  3. icmp-xor-signbit.ll shows the payoff. We don't need to adjust existing icmp patterns 
     to look through bitcasts.
  4. logical-select.ll contains several tests for the or(and,andn) --> select fold to 
     verify that we are still handling those cases. The lone diff shows the movement of 
     the bitcast from the new canonicalization rule.

Differential Revision: https://reviews.llvm.org/D33517



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306011 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjay Patel 2017-06-22 15:46:54 +00:00
parent 3a93e4af81
commit 4c45e36dd8
6 changed files with 52 additions and 55 deletions
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26
lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -1097,20 +1097,11 @@ static Instruction *foldLogicCastConstant(BinaryOperator &Logic, CastInst *Cast,
Type *DestTy = Logic.getType();
Type *SrcTy = Cast->getSrcTy();
// If the first operand is bitcast, move the logic operation ahead of the
// bitcast (do the logic operation in the original type). This can eliminate
// bitcasts and allow combines that would otherwise be impeded by the bitcast.
// Move the logic operation ahead of a zext if the constant is unchanged in
// the smaller source type. Performing the logic in a smaller type may provide
// more information to later folds, and the smaller logic instruction may be
// cheaper (particularly in the case of vectors).
Value *X;
if (match(Cast, m_BitCast(m_Value(X)))) {
Value *NewConstant = ConstantExpr::getBitCast(C, SrcTy);
Value *NewOp = Builder->CreateBinOp(LogicOpc, X, NewConstant);
return CastInst::CreateBitOrPointerCast(NewOp, DestTy);
}
// Similarly, move the logic operation ahead of a zext if the constant is
// unchanged in the smaller source type. Performing the logic in a smaller
// type may provide more information to later folds, and the smaller logic
// instruction may be cheaper (particularly in the case of vectors).
if (match(Cast, m_OneUse(m_ZExt(m_Value(X))))) {
Constant *TruncC = ConstantExpr::getTrunc(C, SrcTy);
Constant *ZextTruncC = ConstantExpr::getZExt(TruncC, DestTy);
@ -1579,11 +1570,14 @@ static Value *getSelectCondition(Value *A, Value *B,
// If A and B are sign-extended, look through the sexts to find the booleans.
Value *Cond;
Value *NotB;
if (match(A, m_SExt(m_Value(Cond))) &&
Cond->getType()->getScalarType()->isIntegerTy(1) &&
match(B, m_CombineOr(m_Not(m_SExt(m_Specific(Cond))),
m_SExt(m_Not(m_Specific(Cond))))))
return Cond;
match(B, m_OneUse(m_Not(m_Value(NotB))))) {
NotB = peekThroughBitcast(NotB, true);
if (match(NotB, m_SExt(m_Specific(Cond))))
return Cond;
}
// All scalar (and most vector) possibilities should be handled now.
// Try more matches that only apply to non-splat constant vectors.

12
lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -1896,6 +1896,18 @@ static Instruction *foldBitCastBitwiseLogic(BitCastInst &BitCast,
return BinaryOperator::Create(BO->getOpcode(), CastedOp0, X);
}
// Canonicalize vector bitcasts to come before vector bitwise logic with a
// constant. This eases recognition of special constants for later ops.
// Example:
// icmp u/s (a ^ signmask), (b ^ signmask) --> icmp s/u a, b
Constant *C;
if (match(BO->getOperand(1), m_Constant(C))) {
// bitcast (logic X, C) --> logic (bitcast X, C')
Value *CastedOp0 = Builder.CreateBitCast(BO->getOperand(0), DestTy);
Value *CastedC = ConstantExpr::getBitCast(C, DestTy);
return BinaryOperator::Create(BO->getOpcode(), CastedOp0, CastedC);
}
return nullptr;
}

18
test/Transforms/InstCombine/bitcast-bigendian.ll
View File

@ -92,12 +92,12 @@ define <2 x float> @test6(float %A){
ret <2 x float> %tmp35
}
; Verify that 'xor' of vector and constant is done as a vector bitwise op before the bitcast.
; No change. Bitcasts are canonicalized above bitwise logic.
define <2 x i32> @xor_bitcast_vec_to_vec(<1 x i64> %a) {
; CHECK-LABEL: @xor_bitcast_vec_to_vec(
; CHECK-NEXT: [[TMP1:%.*]] = xor <1 x i64> [[A:%.*]], <i64 4294967298>
; CHECK-NEXT: [[T2:%.*]] = bitcast <1 x i64> [[TMP1]] to <2 x i32>
; CHECK-NEXT: [[T1:%.*]] = bitcast <1 x i64> [[A:%.*]] to <2 x i32>
; CHECK-NEXT: [[T2:%.*]] = xor <2 x i32> [[T1]], <i32 1, i32 2>
; CHECK-NEXT: ret <2 x i32> [[T2]]
;
%t1 = bitcast <1 x i64> %a to <2 x i32>
@ -105,12 +105,12 @@ define <2 x i32> @xor_bitcast_vec_to_vec(<1 x i64> %a) {
ret <2 x i32> %t2
}
; Verify that 'and' of integer and constant is done as a vector bitwise op before the bitcast.
; No change. Bitcasts are canonicalized above bitwise logic.
define i64 @and_bitcast_vec_to_int(<2 x i32> %a) {
; CHECK-LABEL: @and_bitcast_vec_to_int(
; CHECK-NEXT: [[TMP1:%.*]] = and <2 x i32> [[A:%.*]], <i32 0, i32 3>
; CHECK-NEXT: [[T2:%.*]] = bitcast <2 x i32> [[TMP1]] to i64
; CHECK-NEXT: [[T1:%.*]] = bitcast <2 x i32> [[A:%.*]] to i64
; CHECK-NEXT: [[T2:%.*]] = and i64 [[T1]], 3
; CHECK-NEXT: ret i64 [[T2]]
;
%t1 = bitcast <2 x i32> %a to i64
@ -118,12 +118,12 @@ define i64 @and_bitcast_vec_to_int(<2 x i32> %a) {
ret i64 %t2
}
; Verify that 'or' of vector and constant is done as an integer bitwise op before the bitcast.
; No change. Bitcasts are canonicalized above bitwise logic.
define <2 x i32> @or_bitcast_int_to_vec(i64 %a) {
; CHECK-LABEL: @or_bitcast_int_to_vec(
; CHECK-NEXT: [[TMP1:%.*]] = or i64 [[A:%.*]], 4294967298
; CHECK-NEXT: [[T2:%.*]] = bitcast i64 [[TMP1]] to <2 x i32>
; CHECK-NEXT: [[T1:%.*]] = bitcast i64 [[A:%.*]] to <2 x i32>
; CHECK-NEXT: [[T2:%.*]] = or <2 x i32> [[T1]], <i32 1, i32 2>
; CHECK-NEXT: ret <2 x i32> [[T2]]
;
%t1 = bitcast i64 %a to <2 x i32>

26
test/Transforms/InstCombine/bitcast.ll
View File

@ -31,12 +31,12 @@ define <2 x i32> @xor_two_vector_bitcasts(<1 x i64> %a, <1 x i64> %b) {
ret <2 x i32> %t3
}
; Verify that 'xor' of vector and constant is done as a vector bitwise op before the bitcast.
; No change. Bitcasts are canonicalized above bitwise logic.
define <2 x i32> @xor_bitcast_vec_to_vec(<1 x i64> %a) {
; CHECK-LABEL: @xor_bitcast_vec_to_vec(
; CHECK-NEXT: [[TMP1:%.*]] = xor <1 x i64> [[A:%.*]], <i64 8589934593>
; CHECK-NEXT: [[T2:%.*]] = bitcast <1 x i64> [[TMP1]] to <2 x i32>
; CHECK-NEXT: [[T1:%.*]] = bitcast <1 x i64> [[A:%.*]] to <2 x i32>
; CHECK-NEXT: [[T2:%.*]] = xor <2 x i32> [[T1]], <i32 1, i32 2>
; CHECK-NEXT: ret <2 x i32> [[T2]]
;
%t1 = bitcast <1 x i64> %a to <2 x i32>
@ -44,12 +44,12 @@ define <2 x i32> @xor_bitcast_vec_to_vec(<1 x i64> %a) {
ret <2 x i32> %t2
}
; Verify that 'and' of integer and constant is done as a vector bitwise op before the bitcast.
; No change. Bitcasts are canonicalized above bitwise logic.
define i64 @and_bitcast_vec_to_int(<2 x i32> %a) {
; CHECK-LABEL: @and_bitcast_vec_to_int(
; CHECK-NEXT: [[TMP1:%.*]] = and <2 x i32> [[A:%.*]], <i32 3, i32 0>
; CHECK-NEXT: [[T2:%.*]] = bitcast <2 x i32> [[TMP1]] to i64
; CHECK-NEXT: [[T1:%.*]] = bitcast <2 x i32> [[A:%.*]] to i64
; CHECK-NEXT: [[T2:%.*]] = and i64 [[T1]], 3
; CHECK-NEXT: ret i64 [[T2]]
;
%t1 = bitcast <2 x i32> %a to i64
@ -57,12 +57,12 @@ define i64 @and_bitcast_vec_to_int(<2 x i32> %a) {
ret i64 %t2
}
; Verify that 'or' of vector and constant is done as an integer bitwise op before the bitcast.
; No change. Bitcasts are canonicalized above bitwise logic.
define <2 x i32> @or_bitcast_int_to_vec(i64 %a) {
; CHECK-LABEL: @or_bitcast_int_to_vec(
; CHECK-NEXT: [[TMP1:%.*]] = or i64 [[A:%.*]], 8589934593
; CHECK-NEXT: [[T2:%.*]] = bitcast i64 [[TMP1]] to <2 x i32>
; CHECK-NEXT: [[T1:%.*]] = bitcast i64 [[A:%.*]] to <2 x i32>
; CHECK-NEXT: [[T2:%.*]] = or <2 x i32> [[T1]], <i32 1, i32 2>
; CHECK-NEXT: ret <2 x i32> [[T2]]
;
%t1 = bitcast i64 %a to <2 x i32>
@ -71,7 +71,7 @@ define <2 x i32> @or_bitcast_int_to_vec(i64 %a) {
}
; PR26702 - https://bugs.llvm.org//show_bug.cgi?id=26702
; Bitcast is canonicalized below logic, so we can see the not-not pattern.
; Bitcast is canonicalized above logic, so we can see the not-not pattern.
define <2 x i64> @is_negative(<4 x i32> %x) {
; CHECK-LABEL: @is_negative(
@ -102,12 +102,12 @@ define <4 x i32> @is_negative_bonus_bitcast(<4 x i32> %x) {
ret <4 x i32> %bc2
}
; Negative test: bitcasts are canonicalized below bitwise logic. No changes here.
; Bitcasts are canonicalized above bitwise logic.
define <2 x i8> @canonicalize_bitcast_logic_with_constant(<4 x i4> %x) {
; CHECK-LABEL: @canonicalize_bitcast_logic_with_constant(
; CHECK-NEXT: [[A:%.*]] = and <4 x i4> %x, <i4 0, i4 -8, i4 0, i4 -8>
; CHECK-NEXT: [[B:%.*]] = bitcast <4 x i4> [[A]] to <2 x i8>
; CHECK-NEXT: [[TMP1:%.*]] = bitcast <4 x i4> [[X:%.*]] to <2 x i8>
; CHECK-NEXT: [[B:%.*]] = and <2 x i8> [[TMP1]], <i8 -128, i8 -128>
; CHECK-NEXT: ret <2 x i8> [[B]]
;
%a = and <4 x i4> %x, <i4 0, i4 8, i4 0, i4 8>

21
test/Transforms/InstCombine/icmp-xor-signbit.ll
View File

@ -188,16 +188,13 @@ define <2 x i1> @uge_to_slt_splat(<2 x i8> %x) {
}
; PR33138, part 2: https://bugs.llvm.org/show_bug.cgi?id=33138
; TODO: We could look through vector bitcasts for icmp folds,
; or we could canonicalize bitcast ahead of logic ops with constants.
; Bitcast canonicalization ensures that we recognize the signbit constant.
define <8 x i1> @sgt_to_ugt_bitcasted_splat(<2 x i32> %x, <2 x i32> %y) {
; CHECK-LABEL: @sgt_to_ugt_bitcasted_splat(
; CHECK-NEXT: [[A:%.*]] = xor <2 x i32> %x, <i32 -2139062144, i32 -2139062144>
; CHECK-NEXT: [[B:%.*]] = xor <2 x i32> %y, <i32 -2139062144, i32 -2139062144>
; CHECK-NEXT: [[C:%.*]] = bitcast <2 x i32> [[A]] to <8 x i8>
; CHECK-NEXT: [[D:%.*]] = bitcast <2 x i32> [[B]] to <8 x i8>
; CHECK-NEXT: [[E:%.*]] = icmp sgt <8 x i8> [[C]], [[D]]
; CHECK-NEXT: [[TMP1:%.*]] = bitcast <2 x i32> %x to <8 x i8>
; CHECK-NEXT: [[TMP2:%.*]] = bitcast <2 x i32> %y to <8 x i8>
; CHECK-NEXT: [[E:%.*]] = icmp ugt <8 x i8> [[TMP1]], [[TMP2]]
; CHECK-NEXT: ret <8 x i1> [[E]]
;
%a = xor <2 x i32> %x, <i32 2155905152, i32 2155905152> ; 0x80808080
@ -208,17 +205,11 @@ define <8 x i1> @sgt_to_ugt_bitcasted_splat(<2 x i32> %x, <2 x i32> %y) {
ret <8 x i1> %e
}
; TODO: This is false (little-endian). How should that be recognized?
; Ie, should InstSimplify know this directly, should InstCombine canonicalize
; this so InstSimplify can know this, or is that not something that we want
; either pass to recognize?
; Bitcast canonicalization ensures that we recognize the signbit constant.
define <2 x i1> @negative_simplify_splat(<4 x i8> %x) {
; CHECK-LABEL: @negative_simplify_splat(
; CHECK-NEXT: [[A:%.*]] = or <4 x i8> %x, <i8 0, i8 -128, i8 0, i8 -128>
; CHECK-NEXT: [[B:%.*]] = bitcast <4 x i8> [[A]] to <2 x i16>
; CHECK-NEXT: [[C:%.*]] = icmp sgt <2 x i16> [[B]], zeroinitializer
; CHECK-NEXT: ret <2 x i1> [[C]]
; CHECK-NEXT: ret <2 x i1> zeroinitializer
;
%a = or <4 x i8> %x, <i8 0, i8 128, i8 0, i8 128>
%b = bitcast <4 x i8> %a to <2 x i16>

4
test/Transforms/InstCombine/logical-select.ll
View File

@ -342,8 +342,8 @@ define <2 x i64> @bitcast_select_multi_uses(<4 x i1> %cmp, <2 x i64> %a, <2 x i6
; CHECK-NEXT: [[SEXT:%.*]] = sext <4 x i1> %cmp to <4 x i32>
; CHECK-NEXT: [[BC1:%.*]] = bitcast <4 x i32> [[SEXT]] to <2 x i64>
; CHECK-NEXT: [[AND1:%.*]] = and <2 x i64> [[BC1]], %a
; CHECK-NEXT: [[NEG:%.*]] = xor <4 x i32> [[SEXT]], <i32 -1, i32 -1, i32 -1, i32 -1>
; CHECK-NEXT: [[BC2:%.*]] = bitcast <4 x i32> [[NEG]] to <2 x i64>
; CHECK-NEXT: [[TMP1:%.*]] = bitcast <4 x i32> [[SEXT]] to <2 x i64>
; CHECK-NEXT: [[BC2:%.*]] = xor <2 x i64> [[TMP1]], <i64 -1, i64 -1>
; CHECK-NEXT: [[AND2:%.*]] = and <2 x i64> [[BC2]], %b
; CHECK-NEXT: [[OR:%.*]] = or <2 x i64> [[AND2]], [[AND1]]
; CHECK-NEXT: [[ADD:%.*]] = add <2 x i64> [[AND2]], [[BC2]]