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[InstSimplify] fold funnel shifts with undef operands 

Splitting these off from the D54666.

Patch by: nikic (Nikita Popov)

llvm-svn: 347332
This commit is contained in:
Sanjay Patel 2018-11-20 17:34:59 +00:00
parent 2778f56a40
commit 14ab9170b8
2 changed files with 14 additions and 9 deletions
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11
llvm/lib/Analysis/InstructionSimplify.cpp
View File

@ -5042,7 +5042,16 @@ static Value *simplifyIntrinsic(Function *F, IterTy ArgBegin, IterTy ArgEnd,
}
case Intrinsic::fshl:
case Intrinsic::fshr: {
Value *ShAmtArg = ArgBegin[2];
Value *Op0 = ArgBegin[0], *Op1 = ArgBegin[1], *ShAmtArg = ArgBegin[2];
// If both operands are undef, the result is undef.
if (match(Op0, m_Undef()) && match(Op1, m_Undef()))
return UndefValue::get(F->getReturnType());
// If shift amount is undef, assume it is zero.
if (match(ShAmtArg, m_Undef()))
return ArgBegin[IID == Intrinsic::fshl ? 0 : 1];
const APInt *ShAmtC;
if (match(ShAmtArg, m_APInt(ShAmtC))) {
// If there's effectively no shift, return the 1st arg or 2nd arg.

12
llvm/test/Transforms/InstSimplify/call.ll
View File

@ -632,8 +632,7 @@ define <2 x i8> @fshr_zero_shift_guard_splat(<2 x i8> %x, <2 x i8> %y, <2 x i8>
define i8 @fshl_ops_undef(i8 %shamt) {
; CHECK-LABEL: @fshl_ops_undef(
; CHECK-NEXT: [[R:%.*]] = call i8 @llvm.fshl.i8(i8 undef, i8 undef, i8 [[SHAMT:%.*]])
; CHECK-NEXT: ret i8 [[R]]
; CHECK-NEXT: ret i8 undef
;
%r = call i8 @llvm.fshl.i8(i8 undef, i8 undef, i8 %shamt)
ret i8 %r
@ -641,8 +640,7 @@ define i8 @fshl_ops_undef(i8 %shamt) {
define i9 @fshr_ops_undef(i9 %shamt) {
; CHECK-LABEL: @fshr_ops_undef(
; CHECK-NEXT: [[R:%.*]] = call i9 @llvm.fshr.i9(i9 undef, i9 undef, i9 [[SHAMT:%.*]])
; CHECK-NEXT: ret i9 [[R]]
; CHECK-NEXT: ret i9 undef
;
%r = call i9 @llvm.fshr.i9(i9 undef, i9 undef, i9 %shamt)
ret i9 %r
@ -652,8 +650,7 @@ define i9 @fshr_ops_undef(i9 %shamt) {
define i8 @fshl_shift_undef(i8 %x, i8 %y) {
; CHECK-LABEL: @fshl_shift_undef(
; CHECK-NEXT: [[R:%.*]] = call i8 @llvm.fshl.i8(i8 [[X:%.*]], i8 [[Y:%.*]], i8 undef)
; CHECK-NEXT: ret i8 [[R]]
; CHECK-NEXT: ret i8 [[X:%.*]]
;
%r = call i8 @llvm.fshl.i8(i8 %x, i8 %y, i8 undef)
ret i8 %r
@ -661,8 +658,7 @@ define i8 @fshl_shift_undef(i8 %x, i8 %y) {
define i9 @fshr_shift_undef(i9 %x, i9 %y) {
; CHECK-LABEL: @fshr_shift_undef(
; CHECK-NEXT: [[R:%.*]] = call i9 @llvm.fshr.i9(i9 [[X:%.*]], i9 [[Y:%.*]], i9 undef)
; CHECK-NEXT: ret i9 [[R]]
; CHECK-NEXT: ret i9 [[Y:%.*]]
;
%r = call i9 @llvm.fshr.i9(i9 %x, i9 %y, i9 undef)
ret i9 %r