Add an unfolded offset field to LSR's Formula record. This is used to
model constants which can be added to base registers via add-immediate
instructions which don't require an additional register to materialize
the immediate.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130743 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 5abc790..0d617bf 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -209,7 +209,12 @@
/// when AM.Scale is not zero.
const SCEV *ScaledReg;
- Formula() : ScaledReg(0) {}
+ /// UnfoldedOffset - An additional constant offset which added near the
+ /// use. This requires a temporary register, but the offset itself can
+ /// live in an add immediate field rather than a register.
+ int64_t UnfoldedOffset;
+
+ Formula() : ScaledReg(0), UnfoldedOffset(0) {}
void InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
@@ -379,6 +384,10 @@
OS << "<unknown>";
OS << ')';
}
+ if (UnfoldedOffset != 0) {
+ if (!First) OS << " + "; else First = false;
+ OS << "imm(" << UnfoldedOffset << ')';
+ }
}
void Formula::dump() const {
@@ -771,8 +780,10 @@
RatePrimaryRegister(BaseReg, Regs, L, SE, DT);
}
- if (F.BaseRegs.size() > 1)
- NumBaseAdds += F.BaseRegs.size() - 1;
+ // Determine how many (unfolded) adds we'll need inside the loop.
+ size_t NumBaseParts = F.BaseRegs.size() + (F.UnfoldedOffset != 0);
+ if (NumBaseParts > 1)
+ NumBaseAdds += NumBaseParts - 1;
// Tally up the non-zero immediates.
for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
@@ -1945,7 +1956,8 @@
if (F.BaseRegs == OrigF.BaseRegs &&
F.ScaledReg == OrigF.ScaledReg &&
F.AM.BaseGV == OrigF.AM.BaseGV &&
- F.AM.Scale == OrigF.AM.Scale) {
+ F.AM.Scale == OrigF.AM.Scale &&
+ F.UnfoldedOffset == OrigF.UnfoldedOffset) {
if (F.AM.BaseOffs == 0)
return &LU;
// This is the formula where all the registers and symbols matched;
@@ -2313,8 +2325,29 @@
if (InnerSum->isZero())
continue;
Formula F = Base;
- F.BaseRegs[i] = InnerSum;
- F.BaseRegs.push_back(*J);
+
+ // Add the remaining pieces of the add back into the new formula.
+ const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
+ if (TLI && InnerSumSC &&
+ SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
+ TLI->isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
+ InnerSumSC->getValue()->getZExtValue())) {
+ F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset +
+ InnerSumSC->getValue()->getZExtValue();
+ F.BaseRegs.erase(F.BaseRegs.begin() + i);
+ } else
+ F.BaseRegs[i] = InnerSum;
+
+ // Add J as its own register, or an unfolded immediate.
+ const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
+ if (TLI && SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
+ TLI->isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
+ SC->getValue()->getZExtValue()))
+ F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset +
+ SC->getValue()->getZExtValue();
+ else
+ F.BaseRegs.push_back(*J);
+
if (InsertFormula(LU, LUIdx, F))
// If that formula hadn't been seen before, recurse to find more like
// it.
@@ -2482,6 +2515,13 @@
continue;
}
+ // Check that multiplying with the unfolded offset doesn't overflow.
+ if (F.UnfoldedOffset != 0) {
+ F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
+ if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
+ continue;
+ }
+
// If we make it here and it's legal, add it.
(void)InsertFormula(LU, LUIdx, F);
next:;
@@ -2664,7 +2704,7 @@
// other orig regs.
ImmMapTy::const_iterator OtherImms[] = {
Imms.begin(), prior(Imms.end()),
- Imms.upper_bound((Imms.begin()->first + prior(Imms.end())->first) / 2)
+ Imms.lower_bound((Imms.begin()->first + prior(Imms.end())->first) / 2)
};
for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
ImmMapTy::const_iterator M = OtherImms[i];
@@ -2738,8 +2778,13 @@
Formula NewF = F;
NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm;
if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
- LU.Kind, LU.AccessTy, TLI))
- continue;
+ LU.Kind, LU.AccessTy, TLI)) {
+ if (!TLI ||
+ !TLI->isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
+ continue;
+ NewF = F;
+ NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
+ }
NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
// If the new formula has a constant in a register, and adding the
@@ -3488,6 +3533,14 @@
}
}
+ // Expand the unfolded offset portion.
+ int64_t UnfoldedOffset = F.UnfoldedOffset;
+ if (UnfoldedOffset != 0) {
+ // Just add the immediate values.
+ Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
+ UnfoldedOffset)));
+ }
+
// Emit instructions summing all the operands.
const SCEV *FullS = Ops.empty() ?
SE.getConstant(IntTy, 0) :