diff options
Diffstat (limited to 'lib/CodeGen/OptimizeExts.cpp')
| -rw-r--r-- | lib/CodeGen/OptimizeExts.cpp | 24 |
1 files changed, 22 insertions, 2 deletions
diff --git a/lib/CodeGen/OptimizeExts.cpp b/lib/CodeGen/OptimizeExts.cpp index 41fc204..dcdc243 100644 --- a/lib/CodeGen/OptimizeExts.cpp +++ b/lib/CodeGen/OptimizeExts.cpp @@ -118,6 +118,26 @@ bool OptimizeExts::OptimizeInstr(MachineInstr *MI, MachineBasicBlock *MBB, continue; } + // It's an error to translate this: + // + // %reg1025 = <sext> %reg1024 + // ... + // %reg1026 = SUBREG_TO_REG 0, %reg1024, 4 + // + // into this: + // + // %reg1025 = <sext> %reg1024 + // ... + // %reg1027 = COPY %reg1025:4 + // %reg1026 = SUBREG_TO_REG 0, %reg1027, 4 + // + // The problem here is that SUBREG_TO_REG is there to assert that an + // implicit zext occurs. It doesn't insert a zext instruction. If we allow + // the COPY here, it will give us the value after the <sext>, + // not the original value of %reg1024 before <sext>. + if (UseMI->getOpcode() == TargetOpcode::SUBREG_TO_REG) + continue; + MachineBasicBlock *UseMBB = UseMI->getParent(); if (UseMBB == MBB) { // Local uses that come after the extension. @@ -165,8 +185,8 @@ bool OptimizeExts::OptimizeInstr(MachineInstr *MI, MachineBasicBlock *MBB, continue; unsigned NewVR = MRI->createVirtualRegister(RC); BuildMI(*UseMBB, UseMI, UseMI->getDebugLoc(), - TII->get(TargetOpcode::EXTRACT_SUBREG), NewVR) - .addReg(DstReg).addImm(SubIdx); + TII->get(TargetOpcode::COPY), NewVR) + .addReg(DstReg, 0, SubIdx); UseMO->setReg(NewVR); ++NumReuse; Changed = true; |
