diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp | 10 | ||||
| -rw-r--r-- | lib/Target/README.txt | 13 |
2 files changed, 13 insertions, 10 deletions
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp index 66b6024ba2..3a04ee1e93 100644 --- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp +++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp @@ -1727,7 +1727,8 @@ void SelectionDAGBuilder::visitBitTestCase(BitTestBlock &BB, SDValue ShiftOp = DAG.getCopyFromReg(getControlRoot(), getCurDebugLoc(), Reg, VT); SDValue Cmp; - if (CountPopulation_64(B.Mask) == 1) { + unsigned PopCount = CountPopulation_64(B.Mask); + if (PopCount == 1) { // Testing for a single bit; just compare the shift count with what it // would need to be to shift a 1 bit in that position. Cmp = DAG.getSetCC(getCurDebugLoc(), @@ -1735,6 +1736,13 @@ void SelectionDAGBuilder::visitBitTestCase(BitTestBlock &BB, ShiftOp, DAG.getConstant(CountTrailingZeros_64(B.Mask), VT), ISD::SETEQ); + } else if (PopCount == BB.Range) { + // There is only one zero bit in the range, test for it directly. + Cmp = DAG.getSetCC(getCurDebugLoc(), + TLI.getSetCCResultType(VT), + ShiftOp, + DAG.getConstant(CountTrailingOnes_64(B.Mask), VT), + ISD::SETNE); } else { // Make desired shift SDValue SwitchVal = DAG.getNode(ISD::SHL, getCurDebugLoc(), VT, diff --git a/lib/Target/README.txt b/lib/Target/README.txt index 4e382e8f8e..4cc9534089 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -1762,7 +1762,6 @@ case it choses instead to keep the max operation obvious. //===---------------------------------------------------------------------===// -Switch lowering generates less than ideal code for the following switch: define void @a(i32 %x) nounwind { entry: switch i32 %x, label %if.end [ @@ -1783,19 +1782,15 @@ declare void @foo() Generated code on x86-64 (other platforms give similar results): a: cmpl $5, %edi - ja .LBB0_2 - movl %edi, %eax - movl $47, %ecx - btq %rax, %rcx - jb .LBB0_3 + ja LBB2_2 + cmpl $4, %edi + jne LBB2_3 .LBB0_2: ret .LBB0_3: jmp foo # TAILCALL -The movl+movl+btq+jb could be simplified to a cmpl+jne. - -Or, if we wanted to be really clever, we could simplify the whole thing to +If we wanted to be really clever, we could simplify the whole thing to something like the following, which eliminates a branch: xorl $1, %edi cmpl $4, %edi |