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[ValueTracking, InstCombine] extend isKnownToBeAPowerOfTwo() to handle vector splat constants

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We could try harder to handle non-splat vector constants too, 
but that seems much rarer to me.

Note that the div test isn't resolved because there's a check
for isIntegerTy() guarding that transform.

Differential Revision: http://reviews.llvm.org/D20497

llvm-svn: 270369
This commit is contained in:
Sanjay Patel 2016-05-22 15:41:53 +00:00
parent 7450d33b3c
commit be15a9a346
4 changed files with 8 additions and 13 deletions
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7
lib/Analysis/ValueTracking.cpp
View File

@ -1500,9 +1500,10 @@ bool isKnownToBeAPowerOfTwo(Value *V, bool OrZero, unsigned Depth,
if (Constant *C = dyn_cast<Constant>(V)) {
if (C->isNullValue())
return OrZero;
if (ConstantInt *CI = dyn_cast<ConstantInt>(C))
return CI->getValue().isPowerOf2();
// TODO: Handle vector constants.
const APInt *ConstIntOrConstSplatInt;
if (match(C, m_APInt(ConstIntOrConstSplatInt)))
return ConstIntOrConstSplatInt->isPowerOf2();
}
// 1 << X is clearly a power of two if the one is not shifted off the end. If

2
test/Transforms/InstCombine/div.ll
View File

@ -374,7 +374,7 @@ define i32 @test36(i32 %A) {
define <2 x i32> @test36vec(<2 x i32> %A) {
; CHECK-LABEL: @test36vec(
; CHECK-NEXT: [[AND:%.*]] = and <2 x i32> %A, <i32 2147483647, i32 2147483647>
; CHECK-NEXT: [[SHL:%.*]] = shl nsw <2 x i32> <i32 1, i32 1>, %A
; CHECK-NEXT: [[SHL:%.*]] = shl nuw nsw <2 x i32> <i32 1, i32 1>, %A
; CHECK-NEXT: [[MUL:%.*]] = sdiv exact <2 x i32> [[AND]], [[SHL]]
; CHECK-NEXT: ret <2 x i32> [[MUL]]
;

8
test/Transforms/InstCombine/rem.ll
View File

@ -25,22 +25,18 @@ define i32 @test3(i32 %A) {
ret i32 %B
}
; FIXME: This could be an 'and' just like above.
define <2 x i32> @vec_power_of_2_constant_splat_divisor(<2 x i32> %A) {
; CHECK-LABEL: @vec_power_of_2_constant_splat_divisor(
; CHECK-NEXT: [[B:%.*]] = urem <2 x i32> %A, <i32 8, i32 8>
; CHECK-NEXT: [[B:%.*]] = and <2 x i32> %A, <i32 7, i32 7>
; CHECK-NEXT: ret <2 x i32> [[B]]
;
%B = urem <2 x i32> %A, <i32 8, i32 8>
ret <2 x i32> %B
}
; FIXME: And it shouldn't matter whether we have ConstantVector or ConstantDataVector.
define <2 x i19> @weird_vec_power_of_2_constant_splat_divisor(<2 x i19> %A) {
; CHECK-LABEL: @weird_vec_power_of_2_constant_splat_divisor(
; CHECK-NEXT: [[B:%.*]] = urem <2 x i19> %A, <i19 8, i19 8>
; CHECK-NEXT: [[B:%.*]] = and <2 x i19> %A, <i19 7, i19 7>
; CHECK-NEXT: ret <2 x i19> [[B]]
;
%B = urem <2 x i19> %A, <i19 8, i19 8>

4
test/Transforms/InstCombine/shift.ll
View File

@ -700,11 +700,9 @@ define i32 @test42(i32 %a, i32 %b) nounwind {
ret i32 %div2
}
; FIXME: Vector lshr should be treated the same as scalar.
define <2 x i32> @test42vec(<2 x i32> %a, <2 x i32> %b) {
; CHECK-LABEL: @test42vec(
; CHECK-NEXT: [[DIV:%.*]] = lshr <2 x i32> <i32 4096, i32 4096>, %b
; CHECK-NEXT: [[DIV:%.*]] = lshr exact <2 x i32> <i32 4096, i32 4096>, %b
; CHECK-NEXT: [[DIV2:%.*]] = udiv <2 x i32> %a, [[DIV]]
; CHECK-NEXT: ret <2 x i32> [[DIV2]]
;