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[InstCombine] fold select X, (ext X), C

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If we're going to canonicalize IR towards select of constants, try harder to create those.
Also, don't lose the metadata.

This is actually 4 related transforms in one patch:
      // select X, (sext X), C --> select X, -1, C
      // select X, (zext X), C --> select X,  1, C
      // select X, C, (sext X) --> select X, C, 0
      // select X, C, (zext X) --> select X, C, 0

Differential Revision: https://reviews.llvm.org/D25126


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283575 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjay Patel 2016-10-07 17:53:07 +00:00
parent db695f404d
commit 7a0dadb15b
2 changed files with 29 additions and 17 deletions
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22
lib/Transforms/InstCombine/InstCombineSelect.cpp
View File

@ -939,11 +939,11 @@ Instruction *InstCombiner::foldSelectExtConst(SelectInst &Sel) {
// If the constant is the same after truncation to the smaller type and
// extension to the original type, we can narrow the select.
Value *Cond = Sel.getCondition();
Type *SelType = Sel.getType();
Constant *TruncC = ConstantExpr::getTrunc(C, SmallType);
Constant *ExtC = ConstantExpr::getCast(ExtOpcode, TruncC, SelType);
if (ExtC == C) {
Value *Cond = Sel.getCondition();
Value *TruncCVal = cast<Value>(TruncC);
if (ExtInst == Sel.getFalseValue())
std::swap(X, TruncCVal);
@ -954,6 +954,26 @@ Instruction *InstCombiner::foldSelectExtConst(SelectInst &Sel) {
return CastInst::Create(Instruction::CastOps(ExtOpcode), NewSel, SelType);
}
// If one arm of the select is the extend of the condition, replace that arm
// with the extension of the appropriate known bool value.
if (Cond == X) {
SelectInst *NewSel;
if (ExtInst == Sel.getTrueValue()) {
// select X, (sext X), C --> select X, -1, C
// select X, (zext X), C --> select X, 1, C
Constant *One = ConstantInt::getTrue(SmallType);
Constant *AllOnesOrOne = ConstantExpr::getCast(ExtOpcode, One, SelType);
NewSel = SelectInst::Create(Cond, AllOnesOrOne, C);
} else {
// select X, C, (sext X) --> select X, C, 0
// select X, C, (zext X) --> select X, C, 0
Constant *Zero = ConstantInt::getNullValue(SelType);
NewSel = SelectInst::Create(Cond, C, Zero);
}
NewSel->copyMetadata(Sel);
return NewSel;
}
return nullptr;
}

24
test/Transforms/InstCombine/select-bitext.ll
View File

@ -223,8 +223,7 @@ define <2 x i32> @scalar_select_of_vectors_zext(<2 x i1> %cca, i1 %ccb) {
define i32 @sext_true_val_must_be_all_ones(i1 %x) {
; CHECK-LABEL: @sext_true_val_must_be_all_ones(
; CHECK-NEXT: [[EXT:%.*]] = sext i1 %x to i32
; CHECK-NEXT: [[SEL:%.*]] = select i1 %x, i32 [[EXT]], i32 42, !prof !0
; CHECK-NEXT: [[SEL:%.*]] = select i1 %x, i32 -1, i32 42, !prof !0
; CHECK-NEXT: ret i32 [[SEL]]
;
%ext = sext i1 %x to i32
@ -234,8 +233,7 @@ define i32 @sext_true_val_must_be_all_ones(i1 %x) {
define <2 x i32> @sext_true_val_must_be_all_ones_vec(<2 x i1> %x) {
; CHECK-LABEL: @sext_true_val_must_be_all_ones_vec(
; CHECK-NEXT: [[EXT:%.*]] = sext <2 x i1> %x to <2 x i32>
; CHECK-NEXT: [[SEL:%.*]] = select <2 x i1> %x, <2 x i32> [[EXT]], <2 x i32> <i32 42, i32 12>, !prof !0
; CHECK-NEXT: [[SEL:%.*]] = select <2 x i1> %x, <2 x i32> <i32 -1, i32 -1>, <2 x i32> <i32 42, i32 12>, !prof !0
; CHECK-NEXT: ret <2 x i32> [[SEL]]
;
%ext = sext <2 x i1> %x to <2 x i32>
@ -245,8 +243,7 @@ define <2 x i32> @sext_true_val_must_be_all_ones_vec(<2 x i1> %x) {
define i32 @zext_true_val_must_be_one(i1 %x) {
; CHECK-LABEL: @zext_true_val_must_be_one(
; CHECK-NEXT: [[EXT:%.*]] = zext i1 %x to i32
; CHECK-NEXT: [[SEL:%.*]] = select i1 %x, i32 [[EXT]], i32 42, !prof !0
; CHECK-NEXT: [[SEL:%.*]] = select i1 %x, i32 1, i32 42, !prof !0
; CHECK-NEXT: ret i32 [[SEL]]
;
%ext = zext i1 %x to i32
@ -256,8 +253,7 @@ define i32 @zext_true_val_must_be_one(i1 %x) {
define <2 x i32> @zext_true_val_must_be_one_vec(<2 x i1> %x) {
; CHECK-LABEL: @zext_true_val_must_be_one_vec(
; CHECK-NEXT: [[EXT:%.*]] = zext <2 x i1> %x to <2 x i32>
; CHECK-NEXT: [[SEL:%.*]] = select <2 x i1> %x, <2 x i32> [[EXT]], <2 x i32> <i32 42, i32 12>, !prof !0
; CHECK-NEXT: [[SEL:%.*]] = select <2 x i1> %x, <2 x i32> <i32 1, i32 1>, <2 x i32> <i32 42, i32 12>, !prof !0
; CHECK-NEXT: ret <2 x i32> [[SEL]]
;
%ext = zext <2 x i1> %x to <2 x i32>
@ -267,8 +263,7 @@ define <2 x i32> @zext_true_val_must_be_one_vec(<2 x i1> %x) {
define i32 @sext_false_val_must_be_zero(i1 %x) {
; CHECK-LABEL: @sext_false_val_must_be_zero(
; CHECK-NEXT: [[EXT:%.*]] = sext i1 %x to i32
; CHECK-NEXT: [[SEL:%.*]] = select i1 %x, i32 42, i32 [[EXT]], !prof !0
; CHECK-NEXT: [[SEL:%.*]] = select i1 %x, i32 42, i32 0, !prof !0
; CHECK-NEXT: ret i32 [[SEL]]
;
%ext = sext i1 %x to i32
@ -278,8 +273,7 @@ define i32 @sext_false_val_must_be_zero(i1 %x) {
define <2 x i32> @sext_false_val_must_be_zero_vec(<2 x i1> %x) {
; CHECK-LABEL: @sext_false_val_must_be_zero_vec(
; CHECK-NEXT: [[EXT:%.*]] = sext <2 x i1> %x to <2 x i32>
; CHECK-NEXT: [[SEL:%.*]] = select <2 x i1> %x, <2 x i32> <i32 42, i32 12>, <2 x i32> [[EXT]], !prof !0
; CHECK-NEXT: [[SEL:%.*]] = select <2 x i1> %x, <2 x i32> <i32 42, i32 12>, <2 x i32> zeroinitializer, !prof !0
; CHECK-NEXT: ret <2 x i32> [[SEL]]
;
%ext = sext <2 x i1> %x to <2 x i32>
@ -289,8 +283,7 @@ define <2 x i32> @sext_false_val_must_be_zero_vec(<2 x i1> %x) {
define i32 @zext_false_val_must_be_zero(i1 %x) {
; CHECK-LABEL: @zext_false_val_must_be_zero(
; CHECK-NEXT: [[EXT:%.*]] = zext i1 %x to i32
; CHECK-NEXT: [[SEL:%.*]] = select i1 %x, i32 42, i32 [[EXT]], !prof !0
; CHECK-NEXT: [[SEL:%.*]] = select i1 %x, i32 42, i32 0, !prof !0
; CHECK-NEXT: ret i32 [[SEL]]
;
%ext = zext i1 %x to i32
@ -300,8 +293,7 @@ define i32 @zext_false_val_must_be_zero(i1 %x) {
define <2 x i32> @zext_false_val_must_be_zero_vec(<2 x i1> %x) {
; CHECK-LABEL: @zext_false_val_must_be_zero_vec(
; CHECK-NEXT: [[EXT:%.*]] = zext <2 x i1> %x to <2 x i32>
; CHECK-NEXT: [[SEL:%.*]] = select <2 x i1> %x, <2 x i32> <i32 42, i32 12>, <2 x i32> [[EXT]], !prof !0
; CHECK-NEXT: [[SEL:%.*]] = select <2 x i1> %x, <2 x i32> <i32 42, i32 12>, <2 x i32> zeroinitializer, !prof !0
; CHECK-NEXT: ret <2 x i32> [[SEL]]
;
%ext = zext <2 x i1> %x to <2 x i32>