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[InstCombine] allow vector types for constant folding / computeKnownBits (PR24942) 

computeKnownBits() already works for integer vectors, so allow vector types when calling that from InstCombine.

I don't think the change to use m_APInt in computeKnownBits is strictly necessary because we do check for 
ConstantVector later, but it's more efficient to handle the splat case without needing to loop on vector elements.

This should work with InstSimplify, but doesn't yet, so I made that a FIXME comment on the test for PR24942:
https://llvm.org/bugs/show_bug.cgi?id=24942

Differential Revision: https://reviews.llvm.org/D24677

llvm-svn: 281777
This commit is contained in:
Sanjay Patel 2016-09-16 21:20:36 +00:00
parent b2a0abdf0e
commit c96f6db246
4 changed files with 21 additions and 12 deletions
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7
llvm/lib/Analysis/ValueTracking.cpp
View File

@ -1451,9 +1451,10 @@ void computeKnownBits(const Value *V, APInt &KnownZero, APInt &KnownOne,
KnownOne.getBitWidth() == BitWidth &&
"V, KnownOne and KnownZero should have same BitWidth");
if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
// We know all of the bits for a constant!
KnownOne = CI->getValue();
const APInt *C;
if (match(V, m_APInt(C))) {
// We know all of the bits for a scalar constant or a splat vector constant!
KnownOne = *C;
KnownZero = ~KnownOne;
return;
}

7
llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
View File

@ -2859,13 +2859,14 @@ bool InstCombiner::run() {
// In general, it is possible for computeKnownBits to determine all bits in
// a value even when the operands are not all constants.
if (ExpensiveCombines && !I->use_empty() && I->getType()->isIntegerTy()) {
unsigned BitWidth = I->getType()->getScalarSizeInBits();
Type *Ty = I->getType();
if (ExpensiveCombines && !I->use_empty() && Ty->isIntOrIntVectorTy()) {
unsigned BitWidth = Ty->getScalarSizeInBits();
APInt KnownZero(BitWidth, 0);
APInt KnownOne(BitWidth, 0);
computeKnownBits(I, KnownZero, KnownOne, /*Depth*/0, I);
if ((KnownZero | KnownOne).isAllOnesValue()) {
Constant *C = ConstantInt::get(I->getContext(), KnownOne);
Constant *C = ConstantInt::get(Ty, KnownOne);
DEBUG(dbgs() << "IC: ConstFold (all bits known) to: " << *C <<
" from: " << *I << '\n');

11
llvm/test/Transforms/InstCombine/and.ll
View File

@ -414,3 +414,14 @@ define i32 @test34(i32 %A, i32 %B) {
ret i32 %tmp.4
}
; FIXME: This test should only need -instsimplify (ValueTracking / computeKnownBits), not -instcombine.
define <2 x i32> @PR24942(<2 x i32> %x) {
; CHECK-LABEL: @PR24942(
; CHECK-NEXT: ret <2 x i32> zeroinitializer
;
%lshr = lshr <2 x i32> %x, <i32 31, i32 31>
%and = and <2 x i32> %lshr, <i32 2, i32 2>
ret <2 x i32> %and
}

8
llvm/test/Transforms/InstCombine/trunc.ll
View File

@ -437,9 +437,7 @@ define <8 x i16> @trunc_shl_v8i15_v8i32_15(<8 x i32> %a) {
define <8 x i16> @trunc_shl_v8i16_v8i32_16(<8 x i32> %a) {
; CHECK-LABEL: @trunc_shl_v8i16_v8i32_16(
; CHECK-NEXT: [[SHL:%.*]] = shl <8 x i32> %a, <i32 16, i32 16, i32 16, i32 16, i32 16, i32 16, i32 16, i32 16>
; CHECK-NEXT: [[CONV:%.*]] = trunc <8 x i32> [[SHL]] to <8 x i16>
; CHECK-NEXT: ret <8 x i16> [[CONV]]
; CHECK-NEXT: ret <8 x i16> zeroinitializer
;
%shl = shl <8 x i32> %a, <i32 16, i32 16, i32 16, i32 16, i32 16, i32 16, i32 16, i32 16>
%conv = trunc <8 x i32> %shl to <8 x i16>
@ -448,9 +446,7 @@ define <8 x i16> @trunc_shl_v8i16_v8i32_16(<8 x i32> %a) {
define <8 x i16> @trunc_shl_v8i16_v8i32_17(<8 x i32> %a) {
; CHECK-LABEL: @trunc_shl_v8i16_v8i32_17(
; CHECK-NEXT: [[SHL:%.*]] = shl <8 x i32> %a, <i32 17, i32 17, i32 17, i32 17, i32 17, i32 17, i32 17, i32 17>
; CHECK-NEXT: [[CONV:%.*]] = trunc <8 x i32> [[SHL]] to <8 x i16>
; CHECK-NEXT: ret <8 x i16> [[CONV]]
; CHECK-NEXT: ret <8 x i16> zeroinitializer
;
%shl = shl <8 x i32> %a, <i32 17, i32 17, i32 17, i32 17, i32 17, i32 17, i32 17, i32 17>
%conv = trunc <8 x i32> %shl to <8 x i16>