diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/CodeGen/LowerSubregs.cpp | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/lib/CodeGen/LowerSubregs.cpp b/lib/CodeGen/LowerSubregs.cpp index 9af276fad6..14acb71eeb 100644 --- a/lib/CodeGen/LowerSubregs.cpp +++ b/lib/CodeGen/LowerSubregs.cpp @@ -165,11 +165,12 @@ bool LowerSubregsInstructionPass::LowerSubregToReg(MachineInstr *MI) { unsigned DstReg = MI->getOperand(0).getReg(); unsigned InsReg = MI->getOperand(2).getReg(); - unsigned SubIdx = MI->getOperand(3).getImm(); + unsigned InsSIdx = MI->getOperand(2).getSubReg(); + unsigned SubIdx = MI->getOperand(3).getImm(); assert(SubIdx != 0 && "Invalid index for insert_subreg"); unsigned DstSubReg = TRI.getSubReg(DstReg, SubIdx); - + assert(TargetRegisterInfo::isPhysicalRegister(DstReg) && "Insert destination must be in a physical register"); assert(TargetRegisterInfo::isPhysicalRegister(InsReg) && @@ -177,8 +178,13 @@ bool LowerSubregsInstructionPass::LowerSubregToReg(MachineInstr *MI) { DOUT << "subreg: CONVERTING: " << *MI; - if (DstSubReg == InsReg) { + if (DstSubReg == InsReg && InsSIdx == 0) { // No need to insert an identify copy instruction. + // Watch out for case like this: + // %RAX<def> = ... + // %RAX<def> = SUBREG_TO_REG 0, %EAX:3<kill>, 3 + // The first def is defining RAX, not EAX so the top bits were not + // zero extended. DOUT << "subreg: eliminated!"; } else { // Insert sub-register copy |