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[X86] Prefer andl to andb to save one byte encoding when using with bzhi or bextr #86921

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[X86] Prefer andl to andb to save one byte encoding when using with bzhi or bextr #86921

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21 changes: 18 additions & 3 deletions llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3928,9 +3928,17 @@ bool X86DAGToDAGISel::matchBitExtract(SDNode *Node) {

SDLoc DL(Node);

// Truncate the shift amount.
NBits = CurDAG->getNode(ISD::TRUNCATE, DL, MVT::i8, NBits);
insertDAGNode(*CurDAG, SDValue(Node, 0), NBits);
if (NBits.getSimpleValueType() != MVT::i8) {
// Truncate the shift amount.
NBits = CurDAG->getNode(ISD::TRUNCATE, DL, MVT::i8, NBits);
insertDAGNode(*CurDAG, SDValue(Node, 0), NBits);
}

// Turn (i32)(x & imm8) into (i32)x & imm32.
ConstantSDNode *Imm = nullptr;
if (NBits->getOpcode() == ISD::AND)
if ((Imm = dyn_cast<ConstantSDNode>(NBits->getOperand(1))))
NBits = NBits->getOperand(0);

// Insert 8-bit NBits into lowest 8 bits of 32-bit register.
// All the other bits are undefined, we do not care about them.
Expand All @@ -3945,6 +3953,13 @@ bool X86DAGToDAGISel::matchBitExtract(SDNode *Node) {
0);
insertDAGNode(*CurDAG, SDValue(Node, 0), NBits);

if (Imm) {
NBits =
CurDAG->getNode(ISD::AND, DL, MVT::i32, NBits,
CurDAG->getConstant(Imm->getZExtValue(), DL, MVT::i32));
insertDAGNode(*CurDAG, SDValue(Node, 0), NBits);
}

// We might have matched the amount of high bits to be cleared,
// but we want the amount of low bits to be kept, so negate it then.
if (NegateNBits) {
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4 changes: 2 additions & 2 deletions llvm/test/CodeGen/X86/extract-lowbits.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -439,14 +439,14 @@ define i64 @bzhi64_a0_masked(i64 %val, i64 %numlowbits) nounwind {
;
; X64-BMI1-LABEL: bzhi64_a0_masked:
; X64-BMI1: # %bb.0:
; X64-BMI1-NEXT: andb $63, %sil
; X64-BMI1-NEXT: andl $63, %esi
; X64-BMI1-NEXT: shll $8, %esi
; X64-BMI1-NEXT: bextrq %rsi, %rdi, %rax
; X64-BMI1-NEXT: retq
;
; X64-BMI2-LABEL: bzhi64_a0_masked:
; X64-BMI2: # %bb.0:
; X64-BMI2-NEXT: andb $63, %sil
; X64-BMI2-NEXT: andl $63, %esi
; X64-BMI2-NEXT: bzhiq %rsi, %rdi, %rax
; X64-BMI2-NEXT: retq
%numlowbits.masked = and i64 %numlowbits, 63
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