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Disable ARM partial flag dependency optimization at -Oz

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To not over constrain the scheduler for ARM in thumb mode, some optimizations  for code size reduction, specific to ARM thumb, are blocked when they add a dependency (like write after read dependency).

Disables this check when code size is the priority, i.e., code is compiled with -Oz.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170462 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Quentin Colombet 2012-12-18 22:47:16 +00:00
parent bd7b36e780
commit b519351b87
2 changed files with 44 additions and 2 deletions
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12
lib/Target/ARM/Thumb2SizeReduction.cpp
View File

@ -22,6 +22,7 @@
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Function.h" // To access Function attributes
using namespace llvm;
STATISTIC(NumNarrows, "Number of 32-bit instrs reduced to 16-bit ones");
@ -182,11 +183,14 @@ namespace {
/// ReduceMBB - Reduce width of instructions in the specified basic block.
bool ReduceMBB(MachineBasicBlock &MBB);
bool MinimizeSize;
};
char Thumb2SizeReduce::ID = 0;
}
Thumb2SizeReduce::Thumb2SizeReduce() : MachineFunctionPass(ID) {
MinimizeSize = false;
for (unsigned i = 0, e = array_lengthof(ReduceTable); i != e; ++i) {
unsigned FromOpc = ReduceTable[i].WideOpc;
if (!ReduceOpcodeMap.insert(std::make_pair(FromOpc, i)).second)
@ -221,8 +225,8 @@ static bool HasImplicitCPSRDef(const MCInstrDesc &MCID) {
bool
Thumb2SizeReduce::canAddPseudoFlagDep(MachineInstr *Def, MachineInstr *Use,
bool FirstInSelfLoop) {
// FIXME: Disable check for -Oz (aka OptimizeForSizeHarder).
if (!STI->avoidCPSRPartialUpdate())
// Disable the check for -Oz (aka OptimizeForSizeHarder).
if (MinimizeSize || !STI->avoidCPSRPartialUpdate())
return false;
if (!Def)
@ -942,6 +946,10 @@ bool Thumb2SizeReduce::runOnMachineFunction(MachineFunction &MF) {
TII = static_cast<const Thumb2InstrInfo*>(TM.getInstrInfo());
STI = &TM.getSubtarget<ARMSubtarget>();
// When -Oz is set, the function carries MinSize attribute.
MinimizeSize =
MF.getFunction()->getFnAttributes().hasAttribute(Attributes::MinSize);
bool Modified = false;
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
Modified |= ReduceMBB(*I);

34
test/CodeGen/ARM/avoid-cpsr-rmw.ll
View File

@ -49,3 +49,37 @@ while.body:
while.end:
ret void
}
; Allow partial CPSR dependency when code size is the priority.
; rdar://12878928
define void @t3(i32* nocapture %ptr1, i32* %ptr2, i32 %c) nounwind minsize {
entry:
; CHECK: t3:
%tobool7 = icmp eq i32* %ptr2, null
br i1 %tobool7, label %while.end, label %while.body
while.body:
; CHECK: while.body
; CHECK: mul r{{[0-9]+}}
; CHECK: muls
%ptr1.addr.09 = phi i32* [ %add.ptr, %while.body ], [ %ptr1, %entry ]
%ptr2.addr.08 = phi i32* [ %incdec.ptr, %while.body ], [ %ptr2, %entry ]
%0 = load i32* %ptr1.addr.09, align 4
%arrayidx1 = getelementptr inbounds i32* %ptr1.addr.09, i32 1
%1 = load i32* %arrayidx1, align 4
%arrayidx3 = getelementptr inbounds i32* %ptr1.addr.09, i32 2
%2 = load i32* %arrayidx3, align 4
%arrayidx4 = getelementptr inbounds i32* %ptr1.addr.09, i32 3
%3 = load i32* %arrayidx4, align 4
%add.ptr = getelementptr inbounds i32* %ptr1.addr.09, i32 4
%mul = mul i32 %1, %0
%mul5 = mul i32 %mul, %2
%mul6 = mul i32 %mul5, %3
store i32 %mul6, i32* %ptr2.addr.08, align 4
%incdec.ptr = getelementptr inbounds i32* %ptr2.addr.08, i32 -1
%tobool = icmp eq i32* %incdec.ptr, null
br i1 %tobool, label %while.end, label %while.body
while.end:
ret void
}