From 7d6d4b360fb8c1895b57eeb1284e792f953ea7ee Mon Sep 17 00:00:00 2001 From: Evan Cheng Date: Mon, 23 Mar 2009 07:19:58 +0000 Subject: Do not fold away subreg_to_reg if the source register has a sub-register index. That means the source register is taking a sub-register of a larger register. e.g. On x86 %RAX = ... %RAX = SUBREG_TO_REG 0, %EAX:3, 3 The first def is defining RAX, not EAX so the top bits were not zero-extended. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67511 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/LowerSubregs.cpp | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) (limited to 'lib/CodeGen/LowerSubregs.cpp') 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 = ... + // %RAX = SUBREG_TO_REG 0, %EAX:3, 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 -- cgit v1.2.3-70-g09d2