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Teach loop-reduce to see into nested loops, to pull out immediate values

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pushed down by SCEV.

In a nested loop case, this allows us to emit this:

        lis r3, ha16(L_A$non_lazy_ptr)
        lwz r3, lo16(L_A$non_lazy_ptr)(r3)
        add r2, r2, r3
        li r3, 1
.LBB_foo_2:     ; no_exit.1
        lfd f0, 8(r2)        ;; Uses offset of 8 instead of 0
        stfd f0, 0(r2)
        addi r4, r3, 1
        addi r2, r2, 8
        cmpwi cr0, r3, 100
        or r3, r4, r4
        bne .LBB_foo_2  ; no_exit.1

instead of this:

        lis r3, ha16(L_A$non_lazy_ptr)
        lwz r3, lo16(L_A$non_lazy_ptr)(r3)
        add r2, r2, r3
        addi r3, r3, 8
        li r4, 1
.LBB_foo_2:     ; no_exit.1
        lfd f0, 0(r3)
        stfd f0, 0(r2)
        addi r5, r4, 1
        addi r2, r2, 8
        addi r3, r3, 8
        cmpwi cr0, r4, 100
        or r4, r5, r5
        bne .LBB_foo_2  ; no_exit.1


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@22639 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2005-08-03 23:44:42 +00:00
parent be3e5212e2
commit 7a65839f41
1 changed files with 4 additions and 2 deletions
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6
lib/Transforms/Scalar/LoopStrengthReduce.cpp
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@ -483,8 +483,7 @@ static SCEVHandle GetImmediateValues(SCEVHandle Val, bool isAddress) {
if (isTargetConstant(Val))
return Val;
SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val);
if (SAE) {
if (SCEVAddExpr *SAE = dyn_cast<SCEVAddExpr>(Val)) {
unsigned i = 0;
for (; i != SAE->getNumOperands(); ++i)
if (isTargetConstant(SAE->getOperand(i))) {
@ -497,6 +496,9 @@ static SCEVHandle GetImmediateValues(SCEVHandle Val, bool isAddress) {
ImmVal = SCEVAddExpr::get(ImmVal, SAE->getOperand(i));
return ImmVal;
}
} else if (SCEVAddRecExpr *SARE = dyn_cast<SCEVAddRecExpr>(Val)) {
// Try to pull immediates out of the start value of nested addrec's.
return GetImmediateValues(SARE->getStart(), isAddress);
}
return SCEVUnknown::getIntegerSCEV(0, Val->getType());