implement rdar://6653118 - fastisel should fold loads where possible.
Since mem2reg isn't run at -O0, we get a ton of reloads from the stack,
for example, before, this code:
int foo(int x, int y, int z) {
return x+y+z;
}
used to compile into:
_foo: ## @foo
subq $12, %rsp
movl %edi, 8(%rsp)
movl %esi, 4(%rsp)
movl %edx, (%rsp)
movl 8(%rsp), %edx
movl 4(%rsp), %esi
addl %edx, %esi
movl (%rsp), %edx
addl %esi, %edx
movl %edx, %eax
addq $12, %rsp
ret
Now we produce:
_foo: ## @foo
subq $12, %rsp
movl %edi, 8(%rsp)
movl %esi, 4(%rsp)
movl %edx, (%rsp)
movl 8(%rsp), %edx
addl 4(%rsp), %edx ## Folded load
addl (%rsp), %edx ## Folded load
movl %edx, %eax
addq $12, %rsp
ret
Fewer instructions and less register use = faster compiles.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113102 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86FastISel.cpp b/lib/Target/X86/X86FastISel.cpp
index 0c70eec..9390ba9 100644
--- a/lib/Target/X86/X86FastISel.cpp
+++ b/lib/Target/X86/X86FastISel.cpp
@@ -63,6 +63,13 @@
virtual bool TargetSelectInstruction(const Instruction *I);
+ /// TryToFoldLoad - The specified machine instr operand is a vreg, and that
+ /// vreg is being provided by the specified load instruction. If possible,
+ /// try to fold the load as an operand to the instruction, returning true if
+ /// possible.
+ virtual bool TryToFoldLoad(MachineInstr *MI, unsigned OpNo,
+ const LoadInst *LI);
+
#include "X86GenFastISel.inc"
private:
@@ -1941,6 +1948,34 @@
return ResultReg;
}
+/// TryToFoldLoad - The specified machine instr operand is a vreg, and that
+/// vreg is being provided by the specified load instruction. If possible,
+/// try to fold the load as an operand to the instruction, returning true if
+/// possible.
+bool X86FastISel::TryToFoldLoad(MachineInstr *MI, unsigned OpNo,
+ const LoadInst *LI) {
+ X86AddressMode AM;
+ if (!X86SelectAddress(LI->getOperand(0), AM))
+ return false;
+
+ X86InstrInfo &XII = (X86InstrInfo&)TII;
+
+ unsigned Size = TD.getTypeAllocSize(LI->getType());
+ unsigned Alignment = LI->getAlignment();
+
+ SmallVector<MachineOperand, 8> AddrOps;
+ AM.getFullAddress(AddrOps);
+
+ MachineInstr *Result =
+ XII.foldMemoryOperandImpl(*FuncInfo.MF, MI, OpNo, AddrOps, Size, Alignment);
+ if (Result == 0) return false;
+
+ MI->getParent()->insert(MI, Result);
+ MI->eraseFromParent();
+ return true;
+}
+
+
namespace llvm {
llvm::FastISel *X86::createFastISel(FunctionLoweringInfo &funcInfo) {
return new X86FastISel(funcInfo);
diff --git a/lib/Target/X86/X86InstrBuilder.h b/lib/Target/X86/X86InstrBuilder.h
index 2a6a71d..407b97e 100644
--- a/lib/Target/X86/X86InstrBuilder.h
+++ b/lib/Target/X86/X86InstrBuilder.h
@@ -56,6 +56,31 @@
: BaseType(RegBase), Scale(1), IndexReg(0), Disp(0), GV(0), GVOpFlags(0) {
Base.Reg = 0;
}
+
+
+ void getFullAddress(SmallVectorImpl<MachineOperand> &MO) {
+ assert(Scale == 1 || Scale == 2 || Scale == 4 || Scale == 8);
+
+ if (BaseType == X86AddressMode::RegBase)
+ MO.push_back(MachineOperand::CreateReg(Base.Reg, false, false,
+ false, false, false, 0, false));
+ else {
+ assert(BaseType == X86AddressMode::FrameIndexBase);
+ MO.push_back(MachineOperand::CreateFI(Base.FrameIndex));
+ }
+
+ MO.push_back(MachineOperand::CreateImm(Scale));
+ MO.push_back(MachineOperand::CreateReg(IndexReg, false, false,
+ false, false, false, 0, false));
+
+ if (GV)
+ MO.push_back(MachineOperand::CreateGA(GV, Disp, GVOpFlags));
+ else
+ MO.push_back(MachineOperand::CreateImm(Disp));
+
+ MO.push_back(MachineOperand::CreateReg(0, false, false,
+ false, false, false, 0, false));
+ }
};
/// addDirectMem - This function is used to add a direct memory reference to the
@@ -101,10 +126,11 @@
if (AM.BaseType == X86AddressMode::RegBase)
MIB.addReg(AM.Base.Reg);
- else if (AM.BaseType == X86AddressMode::FrameIndexBase)
+ else {
+ assert(AM.BaseType == X86AddressMode::FrameIndexBase);
MIB.addFrameIndex(AM.Base.FrameIndex);
- else
- assert (0);
+ }
+
MIB.addImm(AM.Scale).addReg(AM.IndexReg);
if (AM.GV)
MIB.addGlobalAddress(AM.GV, AM.Disp, AM.GVOpFlags);
diff --git a/lib/Target/X86/X86InstrInfo.h b/lib/Target/X86/X86InstrInfo.h
index f336206..eb0e4b8 100644
--- a/lib/Target/X86/X86InstrInfo.h
+++ b/lib/Target/X86/X86InstrInfo.h
@@ -845,18 +845,18 @@
/// SetSSEDomain - Set the SSEDomain of MI.
void SetSSEDomain(MachineInstr *MI, unsigned Domain) const;
+ MachineInstr* foldMemoryOperandImpl(MachineFunction &MF,
+ MachineInstr* MI,
+ unsigned OpNum,
+ const SmallVectorImpl<MachineOperand> &MOs,
+ unsigned Size, unsigned Alignment) const;
+
private:
MachineInstr * convertToThreeAddressWithLEA(unsigned MIOpc,
MachineFunction::iterator &MFI,
MachineBasicBlock::iterator &MBBI,
LiveVariables *LV) const;
- MachineInstr* foldMemoryOperandImpl(MachineFunction &MF,
- MachineInstr* MI,
- unsigned OpNum,
- const SmallVectorImpl<MachineOperand> &MOs,
- unsigned Size, unsigned Alignment) const;
-
/// isFrameOperand - Return true and the FrameIndex if the specified
/// operand and follow operands form a reference to the stack frame.
bool isFrameOperand(const MachineInstr *MI, unsigned int Op,