mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-21 18:29:46 +00:00
Teach ValueTracking a new way to analyze PHI nodes, and and teach
Instcombine to be more aggressive about using SimplifyDemandedBits on shift nodes. This allows a shift to be simplified to zero in the included test case. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72204 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
parent
4a4ea14f7d
commit
9004c8afd4
@ -48,8 +48,9 @@ static unsigned getOpcode(const Value *V) {
|
||||
void llvm::ComputeMaskedBits(Value *V, const APInt &Mask,
|
||||
APInt &KnownZero, APInt &KnownOne,
|
||||
TargetData *TD, unsigned Depth) {
|
||||
const unsigned MaxDepth = 6;
|
||||
assert(V && "No Value?");
|
||||
assert(Depth <= 6 && "Limit Search Depth");
|
||||
assert(Depth <= MaxDepth && "Limit Search Depth");
|
||||
unsigned BitWidth = Mask.getBitWidth();
|
||||
assert((V->getType()->isInteger() || isa<PointerType>(V->getType())) &&
|
||||
"Not integer or pointer type!");
|
||||
@ -88,7 +89,7 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask,
|
||||
|
||||
KnownZero.clear(); KnownOne.clear(); // Start out not knowing anything.
|
||||
|
||||
if (Depth == 6 || Mask == 0)
|
||||
if (Depth == MaxDepth || Mask == 0)
|
||||
return; // Limit search depth.
|
||||
|
||||
User *I = dyn_cast<User>(V);
|
||||
@ -522,6 +523,30 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask,
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Otherwise take the unions of the known bit sets of the operands,
|
||||
// taking conservative care to avoid excessive recursion.
|
||||
if (Depth < MaxDepth - 1 && !KnownZero && !KnownOne) {
|
||||
KnownZero = APInt::getAllOnesValue(BitWidth);
|
||||
KnownOne = APInt::getAllOnesValue(BitWidth);
|
||||
for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i) {
|
||||
// Skip direct self references.
|
||||
if (P->getIncomingValue(i) == P) continue;
|
||||
|
||||
KnownZero2 = APInt(BitWidth, 0);
|
||||
KnownOne2 = APInt(BitWidth, 0);
|
||||
// Recurse, but cap the recursion to one level, because we don't
|
||||
// want to waste time spinning around in loops.
|
||||
ComputeMaskedBits(P->getIncomingValue(i), KnownZero | KnownOne,
|
||||
KnownZero2, KnownOne2, TD, MaxDepth-1);
|
||||
KnownZero &= KnownZero2;
|
||||
KnownOne &= KnownOne2;
|
||||
// If all bits have been ruled out, there's no need to check
|
||||
// more operands.
|
||||
if (!KnownZero && !KnownOne)
|
||||
break;
|
||||
}
|
||||
}
|
||||
break;
|
||||
}
|
||||
case Instruction::Call:
|
||||
|
@ -7152,6 +7152,10 @@ Instruction *InstCombiner::commonShiftTransforms(BinaryOperator &I) {
|
||||
return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
|
||||
}
|
||||
|
||||
// See if we can fold away this shift.
|
||||
if (!isa<VectorType>(I.getType()) && SimplifyDemandedInstructionBits(I))
|
||||
return &I;
|
||||
|
||||
// Try to fold constant and into select arguments.
|
||||
if (isa<Constant>(Op0))
|
||||
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
|
||||
@ -7171,8 +7175,6 @@ Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
|
||||
// See if we can simplify any instructions used by the instruction whose sole
|
||||
// purpose is to compute bits we don't care about.
|
||||
uint32_t TypeBits = Op0->getType()->getPrimitiveSizeInBits();
|
||||
if (SimplifyDemandedInstructionBits(I))
|
||||
return &I;
|
||||
|
||||
// shl uint X, 32 = 0 and shr ubyte Y, 9 = 0, ... just don't eliminate shr
|
||||
// of a signed value.
|
||||
|
35
test/Transforms/InstCombine/lshr-phi.ll
Normal file
35
test/Transforms/InstCombine/lshr-phi.ll
Normal file
@ -0,0 +1,35 @@
|
||||
; RUN: llvm-as < %s | opt -instcombine | llvm-dis > %t
|
||||
; RUN: not grep lshr %t
|
||||
; RUN: grep add %t | count 1
|
||||
|
||||
; Instcombine should be able to eliminate the lshr, because only
|
||||
; bits in the operand which might be non-zero will be shifted
|
||||
; off the end.
|
||||
|
||||
define i32 @hash_string(i8* nocapture %key) nounwind readonly {
|
||||
entry:
|
||||
%t0 = load i8* %key, align 1 ; <i8> [#uses=1]
|
||||
%t1 = icmp eq i8 %t0, 0 ; <i1> [#uses=1]
|
||||
br i1 %t1, label %bb2, label %bb
|
||||
|
||||
bb: ; preds = %bb, %entry
|
||||
%indvar = phi i64 [ 0, %entry ], [ %tmp, %bb ] ; <i64> [#uses=2]
|
||||
%k.04 = phi i32 [ 0, %entry ], [ %t8, %bb ] ; <i32> [#uses=2]
|
||||
%cp.05 = getelementptr i8* %key, i64 %indvar ; <i8*> [#uses=1]
|
||||
%t2 = shl i32 %k.04, 1 ; <i32> [#uses=1]
|
||||
%t3 = lshr i32 %k.04, 14 ; <i32> [#uses=1]
|
||||
%t4 = add i32 %t2, %t3 ; <i32> [#uses=1]
|
||||
%t5 = load i8* %cp.05, align 1 ; <i8> [#uses=1]
|
||||
%t6 = sext i8 %t5 to i32 ; <i32> [#uses=1]
|
||||
%t7 = xor i32 %t6, %t4 ; <i32> [#uses=1]
|
||||
%t8 = and i32 %t7, 16383 ; <i32> [#uses=2]
|
||||
%tmp = add i64 %indvar, 1 ; <i64> [#uses=2]
|
||||
%scevgep = getelementptr i8* %key, i64 %tmp ; <i8*> [#uses=1]
|
||||
%t9 = load i8* %scevgep, align 1 ; <i8> [#uses=1]
|
||||
%t10 = icmp eq i8 %t9, 0 ; <i1> [#uses=1]
|
||||
br i1 %t10, label %bb2, label %bb
|
||||
|
||||
bb2: ; preds = %bb, %entry
|
||||
%k.0.lcssa = phi i32 [ 0, %entry ], [ %t8, %bb ] ; <i32> [#uses=1]
|
||||
ret i32 %k.0.lcssa
|
||||
}
|
Loading…
Reference in New Issue
Block a user