[Nouveau] [PATCH 4/4] nv50/ir: allow OP_SET to merge with OP_SET_AND/etc as well as a neg
Ilia Mirkin
imirkin at alum.mit.edu
Fri May 8 22:35:07 PDT 2015
This covers the pattern where a KILL_IF is used, which triggers a
comparison of -x to 0. This can usually be folded into the comparison whose
result is being compared to 0, however it may, itself, have already been
combined with another comparison. That shouldn't impact the logic of
this pass however. With this and the & 1.0 change, code like
00000020: 001c0001 80081df4 set b32 $r0 lt f32 $r0 0x3e800000
00000028: 001c0000 201fc000 and b32 $r0 $r0 0x3f800000
00000030: 7f9c001e dd885c00 set $p0 0x1 lt f32 neg $r0 0x0
00000038: 0000003c 19800000 $p0 discard
becomes
00000020: 001c001d b5881df4 set $p0 0x1 lt f32 $r0 0x3e800000
00000028: 0000003c 19800000 $p0 discard
Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
---
.../drivers/nouveau/codegen/nv50_ir_peephole.cpp | 51 ++++++++++++++--------
1 file changed, 33 insertions(+), 18 deletions(-)
diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
index d8af19a..43a2fe9 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_peephole.cpp
@@ -278,7 +278,6 @@ private:
void tryCollapseChainedMULs(Instruction *, const int s, ImmediateValue&);
- // TGSI 'true' is converted to -1 by F2I(NEG(SET)), track back to SET
CmpInstruction *findOriginForTestWithZero(Value *);
unsigned int foldCount;
@@ -337,16 +336,10 @@ ConstantFolding::findOriginForTestWithZero(Value *value)
return NULL;
Instruction *insn = value->getInsn();
- while (insn && insn->op != OP_SET) {
+ while (insn && insn->op != OP_SET && insn->op != OP_SET_AND &&
+ insn->op != OP_SET_OR && insn->op != OP_SET_XOR) {
Instruction *next = NULL;
switch (insn->op) {
- case OP_NEG:
- case OP_ABS:
- case OP_CVT:
- next = insn->getSrc(0)->getInsn();
- if (insn->sType != next->dType)
- return NULL;
- break;
case OP_MOV:
next = insn->getSrc(0)->getInsn();
break;
@@ -946,29 +939,51 @@ ConstantFolding::opnd(Instruction *i, ImmediateValue &imm0, int s)
case OP_SET: // TODO: SET_AND,OR,XOR
{
+ /* This optimizes the case where the output of a set is being compared
+ * to zero. Since the set can only produce 0/-1 (int) or 0/1 (float), we
+ * can be a lot cleverer in our comparison.
+ */
CmpInstruction *si = findOriginForTestWithZero(i->getSrc(t));
CondCode cc, ccZ;
- if (i->src(t).mod != Modifier(0))
- return;
- if (imm0.reg.data.u32 != 0 || !si || si->op != OP_SET)
+ if (imm0.reg.data.u32 != 0 || !si)
return;
cc = si->setCond;
ccZ = (CondCode)((unsigned int)i->asCmp()->setCond & ~CC_U);
+ // We do everything assuming var (cmp) 0, reverse the condition if 0 is
+ // first.
if (s == 0)
ccZ = reverseCondCode(ccZ);
+ // If there is a negative modifier, we need to undo that, by flipping
+ // the comparison to zero.
+ if (i->src(t).mod.neg())
+ ccZ = reverseCondCode(ccZ);
+ // If this is a signed comparison, we expect the input to be a regular
+ // boolean, i.e. 0/-1. However the rest of the logic assumes that true
+ // is positive, so just flip the sign.
+ if (i->sType == TYPE_S32) {
+ assert(!isFloatType(si->dType));
+ ccZ = reverseCondCode(ccZ);
+ }
switch (ccZ) {
- case CC_LT: cc = CC_FL; break;
- case CC_GE: cc = CC_TR; break;
- case CC_EQ: cc = inverseCondCode(cc); break;
- case CC_LE: cc = inverseCondCode(cc); break;
- case CC_GT: break;
- case CC_NE: break;
+ case CC_LT: cc = CC_FL; break; // bool < 0 -- this is never true
+ case CC_GE: cc = CC_TR; break; // bool >= 0 -- this is always true
+ case CC_EQ: cc = inverseCondCode(cc); break; // bool == 0 -- !bool
+ case CC_LE: cc = inverseCondCode(cc); break; // bool <= 0 -- !bool
+ case CC_GT: break; // bool > 0 -- bool
+ case CC_NE: break; // bool != 0 -- bool
default:
return;
}
+
+ // Update the condition of this SET to be identical to the origin set,
+ // but with the updated condition code. The original SET should get
+ // DCE'd, ideally.
+ i->op = si->op;
i->asCmp()->setCond = cc;
i->setSrc(0, si->src(0));
i->setSrc(1, si->src(1));
+ if (si->srcExists(2))
+ i->setSrc(2, si->src(2));
i->sType = si->sType;
}
break;
--
2.3.6
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