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JIT: more optimizing of float ops based on known input characteristics

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If the inputs are both float singles, and the top half is known to be identical
to the bottom half, we can use packed arithmetic instead of scalar to skip
the movddup.

This is slower on a few rather old CPUs, plus the Atom+Silvermont, so detect
Atom and disable it in that case.

Also avoid PPC_FP on stores if we know that the output came from a float op.
This commit is contained in:
Fiora
2014-10-11 14:22:44 -07:00
parent 4e0591cdf1
commit 72c96c20d3
9 changed files with 154 additions and 39 deletions
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39
Source/Core/Core/PowerPC/PPCAnalyst.cpp
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@@ -830,18 +830,45 @@ u32 PPCAnalyzer::Analyze(u32 address, CodeBlock *block, CodeBuffer *buffer, u32
fprInUse[code[i].fregOut] = true;
}
// Forward scan, for flags that need the other direction for calculation
BitSet32 fprIsSingle;
// Forward scan, for flags that need the other direction for calculation.
BitSet32 fprIsSingle, fprIsDuplicated, fprIsStoreSafe;
for (u32 i = 0; i < block->m_num_instructions; i++)
{
code[i].fprIsSingle = fprIsSingle;
code[i].fprIsDuplicated = fprIsDuplicated;
code[i].fprIsStoreSafe = fprIsStoreSafe;
if (code[i].fregOut >= 0)
{
// This instruction outputs float, so we can omit the special rounding done in fmuls/fmadds
if (code[i].opinfo->type == OPTYPE_SINGLEFP || code[i].opinfo->type == OPTYPE_PS || strncmp(code[i].opinfo->opname, "lfs", 3))
fprIsSingle[code[i].fregOut] = false;
fprIsDuplicated[code[i].fregOut] = false;
fprIsStoreSafe[code[i].fregOut] = false;
// Single, duplicated, and doesn't need PPC_FP.
if (code[i].opinfo->type == OPTYPE_SINGLEFP)
{
fprIsSingle[code[i].fregOut] = true;
else
fprIsSingle[code[i].fregOut] = false;
fprIsDuplicated[code[i].fregOut] = true;
fprIsStoreSafe[code[i].fregOut] = true;
}
// Single and duplicated, but might be a denormal (not safe to skip PPC_FP).
// TODO: if we go directly from a load to store, skip conversion entirely?
// TODO: if we go directly from a load to a float instruction, and the value isn't used
// for anything else, we can skip PPC_FP on a load too.
if (!strncmp(code[i].opinfo->opname, "lfs", 3))
{
fprIsSingle[code[i].fregOut] = true;
fprIsDuplicated[code[i].fregOut] = true;
}
// Paired are still floats, but the top/bottom halves may differ.
if (code[i].opinfo->type == OPTYPE_PS || code[i].opinfo->type == OPTYPE_LOADPS)
{
fprIsSingle[code[i].fregOut] = true;
fprIsStoreSafe[code[i].fregOut] = true;
}
// Careful: changing the float mode in a block breaks this optimization, since
// a previous float op might have had had FTZ off while the later store has FTZ
// on. So, discard all information we have.
if (!strncmp(code[i].opinfo->opname, "mtfs", 4))
fprIsStoreSafe = BitSet32(0);
}
}
return address;