Index: llvm/lib/Target/X86/X86ISelDAGToDAG.cpp =================================================================== --- llvm/lib/Target/X86/X86ISelDAGToDAG.cpp +++ llvm/lib/Target/X86/X86ISelDAGToDAG.cpp @@ -1906,6 +1906,35 @@ break; } + case ISD::ZERO_EXTEND: { + // Try to widen a zexted shift left to the same size as its use, so we can + // match the shift as a scale factor. + if (N.getOperand(0).getOpcode() != ISD::SHL || !N.getOperand(0).hasOneUse()) + break; + + SDValue Shl = N.getOperand(0); + auto *ShAmtC = dyn_cast(Shl.getOperand(1)); + if (!ShAmtC) + break; + + // All of the bits that would have been shifted out must be 0 (nuw). That + // way, the wider shift can't preserve any 1 bits that should get killed. + APInt HighZeros = APInt::getHighBitsSet(Shl.getValueSizeInBits(), + ShAmtC->getZExtValue()); + if (!CurDAG->MaskedValueIsZero(Shl.getOperand(0), HighZeros)) + break; + + // zext (shl X, C) --> shl (zext X), C + MVT VT = N.getSimpleValueType(); + SDLoc DL(N); + SDValue Zext = CurDAG->getNode(ISD::ZERO_EXTEND, DL, VT, Shl.getOperand(0)); + insertDAGNode(*CurDAG, Shl.getOperand(0), Zext); + SDValue NewShl = CurDAG->getNode(ISD::SHL, DL, VT, Zext, Shl.getOperand(1)); + insertDAGNode(*CurDAG, N, NewShl); + if (!matchAddressRecursively(NewShl, AM, Depth + 1)) + return false; + break; + } } return matchAddressBase(N, AM); Index: llvm/test/CodeGen/X86/lea-dagdag.ll =================================================================== --- llvm/test/CodeGen/X86/lea-dagdag.ll +++ llvm/test/CodeGen/X86/lea-dagdag.ll @@ -21,10 +21,10 @@ define i16 @and_i8_shl_zext_add_i16(i16 %t0, i8 %t1) { ; CHECK-LABEL: and_i8_shl_zext_add_i16: ; CHECK: # %bb.0: +; CHECK-NEXT: # kill: def $edi killed $edi def $rdi ; CHECK-NEXT: andb $8, %sil -; CHECK-NEXT: shlb $2, %sil ; CHECK-NEXT: movzbl %sil, %eax -; CHECK-NEXT: addl %edi, %eax +; CHECK-NEXT: leal (%rdi,%rax,4), %eax ; CHECK-NEXT: # kill: def $ax killed $ax killed $eax ; CHECK-NEXT: retq %t4 = and i8 %t1, 8 @@ -52,10 +52,10 @@ define i32 @and_i8_shl_zext_add_i32(i32 %t0, i8 %t1) { ; CHECK-LABEL: and_i8_shl_zext_add_i32: ; CHECK: # %bb.0: +; CHECK-NEXT: # kill: def $edi killed $edi def $rdi ; CHECK-NEXT: andb $8, %sil -; CHECK-NEXT: shlb $2, %sil ; CHECK-NEXT: movzbl %sil, %eax -; CHECK-NEXT: addl %edi, %eax +; CHECK-NEXT: leal (%rdi,%rax,4), %eax ; CHECK-NEXT: retq %t4 = and i8 %t1, 8 %sh = shl i8 %t4, 2 @@ -112,9 +112,8 @@ ; CHECK-LABEL: and_i8_shl_zext_add_i64: ; CHECK: # %bb.0: ; CHECK-NEXT: andb $8, %sil -; CHECK-NEXT: shlb $2, %sil ; CHECK-NEXT: movzbl %sil, %eax -; CHECK-NEXT: addq %rdi, %rax +; CHECK-NEXT: leaq (%rdi,%rax,4), %rax ; CHECK-NEXT: retq %t4 = and i8 %t1, 8 %sh = shl i8 %t4, 2 @@ -142,8 +141,7 @@ ; CHECK: # %bb.0: ; CHECK-NEXT: # kill: def $esi killed $esi def $rsi ; CHECK-NEXT: andl $8, %esi -; CHECK-NEXT: leal (,%rsi,4), %eax -; CHECK-NEXT: addq %rdi, %rax +; CHECK-NEXT: leaq (%rdi,%rsi,4), %rax ; CHECK-NEXT: retq %t4 = and i32 %t1, 8 %sh = shl i32 %t4, 2