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add ARM cmd line option to force always using virtual base regs when possible.

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Intended to help ease reproducing problems by increasing base register usage
after heuristics for only using the when needed are in place.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111930 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jim Grosbach 2010-08-24 18:04:52 +00:00
parent a69e6701a4
commit cd59dc5e81
1 changed files with 16 additions and 4 deletions
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20
lib/Target/ARM/ARMBaseRegisterInfo.cpp
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@ -43,6 +43,9 @@ namespace llvm {
cl::opt<bool>
ReuseFrameIndexVals("arm-reuse-frame-index-vals", cl::Hidden, cl::init(true),
cl::desc("Reuse repeated frame index values"));
cl::opt<bool>
ForceAllBaseRegAlloc("arm-force-base-reg-alloc", cl::Hidden, cl::init(true),
cl::desc("Force use of virtual base registers for stack load/store"));
}
using namespace llvm;
@ -1436,10 +1439,9 @@ needsFrameBaseReg(MachineInstr *MI, unsigned operand) const {
// we don't know everything for certain yet) whether this offset is likely
// to be out of range of the immediate. Return true if so.
// FIXME: For testing, return true for all loads/stores and false for
// everything else. We want to create lots of base regs to shake out bugs.
// We only generate virtual base registers for loads and stores, so
// return false for everything else.
unsigned Opc = MI->getOpcode();
switch (Opc) {
case ARM::LDR: case ARM::LDRH: case ARM::LDRB:
case ARM::STR: case ARM::STRH: case ARM::STRB:
@ -1448,10 +1450,20 @@ needsFrameBaseReg(MachineInstr *MI, unsigned operand) const {
case ARM::VLDRS: case ARM::VLDRD:
case ARM::VSTRS: case ARM::VSTRD:
case ARM::tSTRspi: case ARM::tLDRspi:
return true;
if (ForceAllBaseRegAlloc)
return true;
break;
default:
return false;
}
// FIXME: TODO
// Without a virtual base register, if the function has variable sized
// objects, all fixed-size local references will be via the frame pointer,
// otherwise via the stack pointer. Approximate the offset and see if it's
// legal for the instruction.
return true;
}
/// materializeFrameBaseRegister - Insert defining instruction(s) for