diff options
Diffstat (limited to 'lib/Target/X86/PeepholeOptimizer.cpp')
| -rw-r--r-- | lib/Target/X86/PeepholeOptimizer.cpp | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/lib/Target/X86/PeepholeOptimizer.cpp b/lib/Target/X86/PeepholeOptimizer.cpp index 559baeeae9..efb6cc3e6a 100644 --- a/lib/Target/X86/PeepholeOptimizer.cpp +++ b/lib/Target/X86/PeepholeOptimizer.cpp @@ -51,6 +51,46 @@ bool PH::PeepholeOptimize(MachineBasicBlock &MBB, } return false; + // A large number of X86 instructions have forms which take an 8-bit + // immediate despite the fact that the operands are 16 or 32 bits. Because + // this can save three bytes of code size (and icache space), we want to + // shrink them if possible. + case X86::ADDri16: case X86::ADDri32: + case X86::SUBri16: case X86::SUBri32: + case X86::IMULri16: case X86::IMULri32: + case X86::ANDri16: case X86::ANDri32: + case X86::ORri16: case X86::ORri32: + case X86::XORri16: case X86::XORri32: + assert(MI->getNumOperands() == 3 && "These should all have 3 operands!"); + if (MI->getOperand(2).isImmediate()) { + int Val = MI->getOperand(2).getImmedValue(); + // If the value is the same when signed extended from 8 bits... + if (Val == (signed int)(signed char)Val) { + unsigned Opcode; + switch (MI->getOpcode()) { + default: assert(0 && "Unknown opcode value!"); + case X86::ADDri16: Opcode = X86::ADDri16b; break; + case X86::ADDri32: Opcode = X86::ADDri32b; break; + case X86::SUBri16: Opcode = X86::SUBri16b; break; + case X86::SUBri32: Opcode = X86::SUBri32b; break; + case X86::IMULri16: Opcode = X86::IMULri16b; break; + case X86::IMULri32: Opcode = X86::IMULri32b; break; + case X86::ANDri16: Opcode = X86::ANDri16b; break; + case X86::ANDri32: Opcode = X86::ANDri32b; break; + case X86::ORri16: Opcode = X86::ORri16b; break; + case X86::ORri32: Opcode = X86::ORri32b; break; + case X86::XORri16: Opcode = X86::XORri16b; break; + case X86::XORri32: Opcode = X86::XORri32b; break; + } + unsigned R0 = MI->getOperand(0).getReg(); + unsigned R1 = MI->getOperand(1).getReg(); + *I = BuildMI(Opcode, 2, R0).addReg(R1).addZImm((char)Val); + delete MI; + return true; + } + } + return false; + #if 0 case X86::MOVir32: Size++; case X86::MOVir16: Size++; |