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[ConstantFolding] improve folding of binops with vector undef operand

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A non-undef operand may still have undef constant elements, 
so we should always propagate the vector results per-lane.

llvm-svn: 340194
This commit is contained in:
Sanjay Patel 2018-08-20 18:19:02 +00:00
parent 8e1b93caef
commit c684399bd3
2 changed files with 17 additions and 17 deletions
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18
lib/IR/ConstantFold.cpp
View File

@ -916,13 +916,14 @@ Constant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg,
return ConstantVector::get(Result);
}
Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
Constant *C1, Constant *C2) {
Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, Constant *C1,
Constant *C2) {
assert(Instruction::isBinaryOp(Opcode) && "Non-binary instruction detected");
// Handle UndefValue up front.
if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
// Handle scalar UndefValue. Vectors are always evaluated per element.
bool HasScalarUndef = !C1->getType()->isVectorTy() &&
(isa<UndefValue>(C1) || isa<UndefValue>(C2));
if (HasScalarUndef) {
switch (static_cast<Instruction::BinaryOps>(Opcode)) {
case Instruction::Xor:
if (isa<UndefValue>(C1) && isa<UndefValue>(C2))
@ -1024,9 +1025,8 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
}
}
// At this point neither constant should be an UndefValue.
assert(!isa<UndefValue>(C1) && !isa<UndefValue>(C2) &&
"Unexpected UndefValue");
// Neither constant should be UndefValue, unless these are vector constants.
assert(!HasScalarUndef && "Unexpected UndefValue");
// Handle simplifications when the RHS is a constant int.
if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) {
@ -1218,7 +1218,7 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
}
}
} else if (VectorType *VTy = dyn_cast<VectorType>(C1->getType())) {
// Perform elementwise folding.
// Fold each element and create a vector constant from those constants.
SmallVector<Constant*, 16> Result;
Type *Ty = IntegerType::get(VTy->getContext(), 32);
for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) {

16
test/Analysis/ConstantFolding/vector-undef-elts.ll
View File

@ -1,11 +1,11 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -constprop -S -o - | FileCheck %s
; FIXME: When both operands are undef in a lane, that lane should produce an undef result.
; When both operands are undef in a lane, that lane should produce an undef result.
define <3 x i8> @shl() {
; CHECK-LABEL: @shl(
; CHECK-NEXT: ret <3 x i8> zeroinitializer
; CHECK-NEXT: ret <3 x i8> <i8 undef, i8 0, i8 0>
;
%c = shl <3 x i8> undef, <i8 undef, i8 4, i8 1>
ret <3 x i8> %c
@ -13,7 +13,7 @@ define <3 x i8> @shl() {
define <3 x i8> @and() {
; CHECK-LABEL: @and(
; CHECK-NEXT: ret <3 x i8> zeroinitializer
; CHECK-NEXT: ret <3 x i8> <i8 undef, i8 0, i8 undef>
;
%c = and <3 x i8> <i8 undef, i8 42, i8 undef>, undef
ret <3 x i8> %c
@ -21,7 +21,7 @@ define <3 x i8> @and() {
define <3 x i8> @and_commute() {
; CHECK-LABEL: @and_commute(
; CHECK-NEXT: ret <3 x i8> zeroinitializer
; CHECK-NEXT: ret <3 x i8> <i8 0, i8 0, i8 undef>
;
%c = and <3 x i8> undef, <i8 -42, i8 42, i8 undef>
ret <3 x i8> %c
@ -29,7 +29,7 @@ define <3 x i8> @and_commute() {
define <3 x i8> @or() {
; CHECK-LABEL: @or(
; CHECK-NEXT: ret <3 x i8> <i8 -1, i8 -1, i8 -1>
; CHECK-NEXT: ret <3 x i8> <i8 undef, i8 -1, i8 undef>
;
%c = or <3 x i8> <i8 undef, i8 42, i8 undef>, undef
ret <3 x i8> %c
@ -37,7 +37,7 @@ define <3 x i8> @or() {
define <3 x i8> @or_commute() {
; CHECK-LABEL: @or_commute(
; CHECK-NEXT: ret <3 x i8> <i8 -1, i8 -1, i8 -1>
; CHECK-NEXT: ret <3 x i8> <i8 -1, i8 -1, i8 undef>
;
%c = or <3 x i8> undef, <i8 -42, i8 42, i8 undef>
ret <3 x i8> %c
@ -45,7 +45,7 @@ define <3 x i8> @or_commute() {
define <3 x float> @fadd() {
; CHECK-LABEL: @fadd(
; CHECK-NEXT: ret <3 x float> <float 0x7FF8000000000000, float 0x7FF8000000000000, float 0x7FF8000000000000>
; CHECK-NEXT: ret <3 x float> <float undef, float 0x7FF8000000000000, float undef>
;
%c = fadd <3 x float> <float undef, float 42.0, float undef>, undef
ret <3 x float> %c
@ -53,7 +53,7 @@ define <3 x float> @fadd() {
define <3 x float> @fadd_commute() {
; CHECK-LABEL: @fadd_commute(
; CHECK-NEXT: ret <3 x float> <float 0x7FF8000000000000, float 0x7FF8000000000000, float 0x7FF8000000000000>
; CHECK-NEXT: ret <3 x float> <float 0x7FF8000000000000, float 0x7FF8000000000000, float undef>
;
%c = fadd <3 x float> undef, <float -42.0, float 42.0, float undef>
ret <3 x float> %c