Changes in directory llvm/lib/CodeGen/SelectionDAG:
DAGCombiner.cpp updated: 1.217 -> 1.218 --- Log message: Lower X%C into X/C+stuff. This allows the 'division by a constant' logic to apply to rems as well as divs. This fixes PR945: http://llvm.org/PR945 and speeds up ReedSolomon from 14.57s to 10.90s (which is now faster than gcc). It compiles CodeGen/X86/rem.ll into: _test1: subl $4, %esp movl %esi, (%esp) movl $2155905153, %ecx movl 8(%esp), %esi movl %esi, %eax imull %ecx addl %esi, %edx movl %edx, %eax shrl $31, %eax sarl $7, %edx addl %eax, %edx imull $255, %edx, %eax subl %eax, %esi movl %esi, %eax movl (%esp), %esi addl $4, %esp ret _test2: movl 4(%esp), %eax movl %eax, %ecx sarl $31, %ecx shrl $24, %ecx addl %eax, %ecx andl $4294967040, %ecx subl %ecx, %eax ret _test3: subl $4, %esp movl %esi, (%esp) movl $2155905153, %ecx movl 8(%esp), %esi movl %esi, %eax mull %ecx shrl $7, %edx imull $255, %edx, %eax subl %eax, %esi movl %esi, %eax movl (%esp), %esi addl $4, %esp ret instead of div/idiv instructions. --- Diffs of the changes: (+24 -0) DAGCombiner.cpp | 24 ++++++++++++++++++++++++ 1 files changed, 24 insertions(+) Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp diff -u llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.217 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.218 --- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.217 Thu Oct 12 15:23:19 2006 +++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Thu Oct 12 15:58:32 2006 @@ -885,6 +885,18 @@ if (TLI.MaskedValueIsZero(N1, SignBit) && TLI.MaskedValueIsZero(N0, SignBit)) return DAG.getNode(ISD::UREM, VT, N0, N1); + + // Unconditionally lower X%C -> X-X/C*C. This allows the X/C logic to hack on + // the remainder operation. + if (N1C && !N1C->isNullValue()) { + SDOperand Div = DAG.getNode(ISD::SDIV, VT, N0, N1); + SDOperand Mul = DAG.getNode(ISD::MUL, VT, Div, N1); + SDOperand Sub = DAG.getNode(ISD::SUB, VT, N0, Mul); + AddToWorkList(Div.Val); + AddToWorkList(Mul.Val); + return Sub; + } + return SDOperand(); } @@ -911,6 +923,18 @@ } } } + + // Unconditionally lower X%C -> X-X/C*C. This allows the X/C logic to hack on + // the remainder operation. + if (N1C && !N1C->isNullValue()) { + SDOperand Div = DAG.getNode(ISD::UDIV, VT, N0, N1); + SDOperand Mul = DAG.getNode(ISD::MUL, VT, Div, N1); + SDOperand Sub = DAG.getNode(ISD::SUB, VT, N0, Mul); + AddToWorkList(Div.Val); + AddToWorkList(Mul.Val); + return Sub; + } + return SDOperand(); } _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
