forked from OSchip/llvm-project
[InstCombine] PR37603: low bit mask canonicalization
Summary: This is [[ https://bugs.llvm.org/show_bug.cgi?id=37603 | PR37603 ]]. https://godbolt.org/g/VCMNpS https://rise4fun.com/Alive/idM When doing bit manipulations, it is quite common to calculate some bit mask, and apply it to some value via `and`. The typical C code looks like: ``` int mask_signed_add(int nbits) { return (1 << nbits) - 1; } ``` which is translated into (with `-O3`) ``` define dso_local i32 @mask_signed_add(int)(i32) local_unnamed_addr #0 { %2 = shl i32 1, %0 %3 = add nsw i32 %2, -1 ret i32 %3 } ``` But there is a second, less readable variant: ``` int mask_signed_xor(int nbits) { return ~(-(1 << nbits)); } ``` which is translated into (with `-O3`) ``` define dso_local i32 @mask_signed_xor(int)(i32) local_unnamed_addr #0 { %2 = shl i32 -1, %0 %3 = xor i32 %2, -1 ret i32 %3 } ``` Since we created such a mask, it is quite likely that we will use it in `and` next. And then we may get rid of `not` op by folding into `andn`. But now that i have actually looked: https://godbolt.org/g/VTUDmU _some_ backend changes will be needed too. We clearly loose `bzhi` recognition. Reviewers: spatel, craig.topper, RKSimon Reviewed By: spatel Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D47428 llvm-svn: 334127
This commit is contained in:
Roman Lebedev
parent
4771bc6c35
commit
cbf8446359
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@ -1096,6 +1096,30 @@ Value *InstCombiner::SimplifyAddWithRemainder(BinaryOperator &I) {
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return nullptr;
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}
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/// Fold
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/// (1 << NBits) - 1
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/// Into:
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/// ~(-(1 << NBits))
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/// Because a 'not' is better for bit-tracking analysis and other transforms
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/// than an 'add'. The new shl is always nsw, and is nuw if old `and` was.
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static Instruction *canonicalizeLowbitMask(BinaryOperator &I,
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InstCombiner::BuilderTy &Builder) {
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Value *NBits;
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if (!match(&I, m_Add(m_OneUse(m_Shl(m_One(), m_Value(NBits))), m_AllOnes())))
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return nullptr;
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Constant *MinusOne = Constant::getAllOnesValue(NBits->getType());
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Value *NotMask = Builder.CreateShl(MinusOne, NBits, "notmask");
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// Be wary of constant folding.
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if (auto *BOp = dyn_cast<BinaryOperator>(NotMask)) {
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// Always NSW. But NUW propagates from `add`.
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BOp->setHasNoSignedWrap();
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BOp->setHasNoUnsignedWrap(I.hasNoUnsignedWrap());
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}
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return BinaryOperator::CreateNot(NotMask, I.getName());
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}
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Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
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bool Changed = SimplifyAssociativeOrCommutative(I);
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Value *LHS = I.getOperand(0), *RHS = I.getOperand(1);
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@ -1347,6 +1371,9 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
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I.setHasNoUnsignedWrap(true);
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}
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if (Instruction *V = canonicalizeLowbitMask(I, Builder))
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return V;
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return Changed ? &I : nullptr;
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}
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@ -314,8 +314,8 @@ define i64 @test14(i64 %x, i32 %y) {
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define i64 @test15(i32 %x, i32 %y) {
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; CHECK-LABEL: @test15(
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; CHECK-NEXT: [[SHL:%.*]] = shl nuw i32 1, [[Y:%.*]]
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; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[SHL]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nsw i32 -1, [[Y:%.*]]
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; CHECK-NEXT: [[TMP1:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: [[TMP2:%.*]] = and i32 [[TMP1]], [[X:%.*]]
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; CHECK-NEXT: [[UREM:%.*]] = zext i32 [[TMP2]] to i64
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; CHECK-NEXT: ret i64 [[UREM]]
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@ -17,8 +17,8 @@
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define i32 @shl_add(i32 %NBits) {
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; CHECK-LABEL: @shl_add(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl i32 1, %NBits
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@ -28,8 +28,8 @@ define i32 @shl_add(i32 %NBits) {
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define i32 @shl_add_nsw(i32 %NBits) {
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; CHECK-LABEL: @shl_add_nsw(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add nsw i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl i32 1, %NBits
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@ -39,8 +39,8 @@ define i32 @shl_add_nsw(i32 %NBits) {
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define i32 @shl_add_nuw(i32 %NBits) {
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; CHECK-LABEL: @shl_add_nuw(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add nuw i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nuw nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl i32 1, %NBits
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@ -50,8 +50,8 @@ define i32 @shl_add_nuw(i32 %NBits) {
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define i32 @shl_add_nsw_nuw(i32 %NBits) {
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; CHECK-LABEL: @shl_add_nsw_nuw(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add nuw nsw i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nuw nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl i32 1, %NBits
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@ -63,8 +63,8 @@ define i32 @shl_add_nsw_nuw(i32 %NBits) {
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define i32 @shl_nsw_add(i32 %NBits) {
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; CHECK-LABEL: @shl_nsw_add(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl nsw i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl nsw i32 1, %NBits
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@ -74,8 +74,8 @@ define i32 @shl_nsw_add(i32 %NBits) {
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define i32 @shl_nsw_add_nsw(i32 %NBits) {
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; CHECK-LABEL: @shl_nsw_add_nsw(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl nsw i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add nsw i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl nsw i32 1, %NBits
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@ -85,8 +85,8 @@ define i32 @shl_nsw_add_nsw(i32 %NBits) {
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define i32 @shl_nsw_add_nuw(i32 %NBits) {
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; CHECK-LABEL: @shl_nsw_add_nuw(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl nsw i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add nuw i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nuw nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl nsw i32 1, %NBits
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@ -96,8 +96,8 @@ define i32 @shl_nsw_add_nuw(i32 %NBits) {
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define i32 @shl_nsw_add_nsw_nuw(i32 %NBits) {
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; CHECK-LABEL: @shl_nsw_add_nsw_nuw(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl nsw i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add nuw nsw i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nuw nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl nsw i32 1, %NBits
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@ -109,8 +109,8 @@ define i32 @shl_nsw_add_nsw_nuw(i32 %NBits) {
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define i32 @shl_nuw_add(i32 %NBits) {
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; CHECK-LABEL: @shl_nuw_add(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl nuw i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl nuw i32 1, %NBits
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@ -120,8 +120,8 @@ define i32 @shl_nuw_add(i32 %NBits) {
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define i32 @shl_nuw_add_nsw(i32 %NBits) {
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; CHECK-LABEL: @shl_nuw_add_nsw(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl nuw i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add nsw i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl nuw i32 1, %NBits
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@ -131,8 +131,8 @@ define i32 @shl_nuw_add_nsw(i32 %NBits) {
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define i32 @shl_nuw_add_nuw(i32 %NBits) {
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; CHECK-LABEL: @shl_nuw_add_nuw(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl nuw i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add nuw i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nuw nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl nuw i32 1, %NBits
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@ -142,8 +142,8 @@ define i32 @shl_nuw_add_nuw(i32 %NBits) {
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define i32 @shl_nuw_add_nsw_nuw(i32 %NBits) {
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; CHECK-LABEL: @shl_nuw_add_nsw_nuw(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl nuw i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add nuw nsw i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nuw nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl nuw i32 1, %NBits
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@ -155,8 +155,8 @@ define i32 @shl_nuw_add_nsw_nuw(i32 %NBits) {
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define i32 @shl_nsw_nuw_add(i32 %NBits) {
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; CHECK-LABEL: @shl_nsw_nuw_add(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl nuw nsw i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl nuw nsw i32 1, %NBits
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@ -166,8 +166,8 @@ define i32 @shl_nsw_nuw_add(i32 %NBits) {
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define i32 @shl_nsw_nuw_add_nsw(i32 %NBits) {
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; CHECK-LABEL: @shl_nsw_nuw_add_nsw(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl nuw nsw i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add nsw i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl nuw nsw i32 1, %NBits
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@ -177,8 +177,8 @@ define i32 @shl_nsw_nuw_add_nsw(i32 %NBits) {
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define i32 @shl_nsw_nuw_add_nuw(i32 %NBits) {
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; CHECK-LABEL: @shl_nsw_nuw_add_nuw(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl nuw nsw i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add nuw i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nuw nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl nuw nsw i32 1, %NBits
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@ -188,8 +188,8 @@ define i32 @shl_nsw_nuw_add_nuw(i32 %NBits) {
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define i32 @shl_nsw_nuw_add_nsw_nuw(i32 %NBits) {
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; CHECK-LABEL: @shl_nsw_nuw_add_nsw_nuw(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl nuw nsw i32 1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add nuw nsw i32 [[SETBIT]], -1
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nuw nsw i32 -1, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor i32 [[NOTMASK]], -1
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; CHECK-NEXT: ret i32 [[RET]]
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;
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%setbit = shl nuw nsw i32 1, %NBits
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@ -203,8 +203,8 @@ define i32 @shl_nsw_nuw_add_nsw_nuw(i32 %NBits) {
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define <2 x i32> @shl_add_vec(<2 x i32> %NBits) {
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; CHECK-LABEL: @shl_add_vec(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl <2 x i32> <i32 1, i32 1>, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add <2 x i32> [[SETBIT]], <i32 -1, i32 -1>
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nsw <2 x i32> <i32 -1, i32 -1>, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor <2 x i32> [[NOTMASK]], <i32 -1, i32 -1>
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; CHECK-NEXT: ret <2 x i32> [[RET]]
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;
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%setbit = shl <2 x i32> <i32 1, i32 1>, %NBits
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@ -214,8 +214,8 @@ define <2 x i32> @shl_add_vec(<2 x i32> %NBits) {
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define <3 x i32> @shl_add_vec_undef0(<3 x i32> %NBits) {
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; CHECK-LABEL: @shl_add_vec_undef0(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl <3 x i32> <i32 1, i32 undef, i32 1>, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add <3 x i32> [[SETBIT]], <i32 -1, i32 -1, i32 -1>
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nsw <3 x i32> <i32 -1, i32 -1, i32 -1>, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor <3 x i32> [[NOTMASK]], <i32 -1, i32 -1, i32 -1>
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; CHECK-NEXT: ret <3 x i32> [[RET]]
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;
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%setbit = shl <3 x i32> <i32 1, i32 undef, i32 1>, %NBits
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@ -225,8 +225,8 @@ define <3 x i32> @shl_add_vec_undef0(<3 x i32> %NBits) {
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define <3 x i32> @shl_add_vec_undef1(<3 x i32> %NBits) {
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; CHECK-LABEL: @shl_add_vec_undef1(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl <3 x i32> <i32 1, i32 1, i32 1>, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add <3 x i32> [[SETBIT]], <i32 -1, i32 undef, i32 -1>
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nsw <3 x i32> <i32 -1, i32 -1, i32 -1>, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor <3 x i32> [[NOTMASK]], <i32 -1, i32 -1, i32 -1>
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; CHECK-NEXT: ret <3 x i32> [[RET]]
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;
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%setbit = shl <3 x i32> <i32 1, i32 1, i32 1>, %NBits
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@ -236,8 +236,8 @@ define <3 x i32> @shl_add_vec_undef1(<3 x i32> %NBits) {
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define <3 x i32> @shl_add_vec_undef2(<3 x i32> %NBits) {
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; CHECK-LABEL: @shl_add_vec_undef2(
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; CHECK-NEXT: [[SETBIT:%.*]] = shl <3 x i32> <i32 1, i32 undef, i32 1>, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = add <3 x i32> [[SETBIT]], <i32 -1, i32 undef, i32 -1>
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; CHECK-NEXT: [[NOTMASK:%.*]] = shl nsw <3 x i32> <i32 -1, i32 -1, i32 -1>, [[NBITS:%.*]]
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; CHECK-NEXT: [[RET:%.*]] = xor <3 x i32> [[NOTMASK]], <i32 -1, i32 -1, i32 -1>
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; CHECK-NEXT: ret <3 x i32> [[RET]]
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;
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%setbit = shl <3 x i32> <i32 1, i32 undef, i32 1>, %NBits
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