[llvm] r224213 - [PowerPC] Handle cmp op promotion for SELECT[_CC] nodes in PPCTL::DAGCombineExtBoolTrunc
Hal Finkel
hfinkel at anl.gov
Sat Dec 13 21:53:19 PST 2014
Author: hfinkel
Date: Sat Dec 13 23:53:19 2014
New Revision: 224213
URL: http://llvm.org/viewvc/llvm-project?rev=224213&view=rev
Log:
[PowerPC] Handle cmp op promotion for SELECT[_CC] nodes in PPCTL::DAGCombineExtBoolTrunc
PPCTargetLowering::DAGCombineExtBoolTrunc contains logic to remove unwanted
truncations and extensions when dealing with nodes of the form:
zext(binary-ops(binary-ops(trunc(x), trunc(y)), ...)
There was a FIXME in the implementation (now removed) regarding the fact that
the function would abort the transformations if any of the non-output operands
of a SELECT or SELECT_CC node would need to be promoted (because they were
also output operands, for example). As a result, we continued to generate
unnecessary zero-extends for code such as this:
unsigned foo(unsigned a, unsigned b) {
return (a <= b) ? a : b;
}
which would produce:
cmplw 0, 3, 4
isel 3, 4, 3, 1
rldicl 3, 3, 0, 32
blr
and now we produce:
cmplw 0, 3, 4
isel 3, 4, 3, 1
blr
which is better in the obvious way.
Modified:
llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp
llvm/trunk/test/CodeGen/PowerPC/rm-zext.ll
Modified: llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp?rev=224213&r1=224212&r2=224213&view=diff
==============================================================================
--- llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp Sat Dec 13 23:53:19 2014
@@ -8127,6 +8127,10 @@ SDValue PPCTargetLowering::DAGCombineExt
}
}
+ // The operands of a select that must be truncated when the select is
+ // promoted because the operand is actually part of the to-be-promoted set.
+ DenseMap<SDNode *, EVT> SelectTruncOp[2];
+
// Make sure that this is a self-contained cluster of operations (which
// is not quite the same thing as saying that everything has only one
// use).
@@ -8141,18 +8145,19 @@ SDValue PPCTargetLowering::DAGCombineExt
if (User != N && !Visited.count(User))
return SDValue();
- // Make sure that we're not going to promote the non-output-value
- // operand(s) or SELECT or SELECT_CC.
- // FIXME: Although we could sometimes handle this, and it does occur in
- // practice that one of the condition inputs to the select is also one of
- // the outputs, we currently can't deal with this.
+ // If we're going to promote the non-output-value operand(s) or SELECT or
+ // SELECT_CC, record them for truncation.
if (User->getOpcode() == ISD::SELECT) {
if (User->getOperand(0) == Inputs[i])
- return SDValue();
+ SelectTruncOp[0].insert(std::make_pair(User,
+ User->getOperand(0).getValueType()));
} else if (User->getOpcode() == ISD::SELECT_CC) {
- if (User->getOperand(0) == Inputs[i] ||
- User->getOperand(1) == Inputs[i])
- return SDValue();
+ if (User->getOperand(0) == Inputs[i])
+ SelectTruncOp[0].insert(std::make_pair(User,
+ User->getOperand(0).getValueType()));
+ if (User->getOperand(1) == Inputs[i])
+ SelectTruncOp[1].insert(std::make_pair(User,
+ User->getOperand(1).getValueType()));
}
}
}
@@ -8165,18 +8170,19 @@ SDValue PPCTargetLowering::DAGCombineExt
if (User != N && !Visited.count(User))
return SDValue();
- // Make sure that we're not going to promote the non-output-value
- // operand(s) or SELECT or SELECT_CC.
- // FIXME: Although we could sometimes handle this, and it does occur in
- // practice that one of the condition inputs to the select is also one of
- // the outputs, we currently can't deal with this.
+ // If we're going to promote the non-output-value operand(s) or SELECT or
+ // SELECT_CC, record them for truncation.
if (User->getOpcode() == ISD::SELECT) {
if (User->getOperand(0) == PromOps[i])
- return SDValue();
+ SelectTruncOp[0].insert(std::make_pair(User,
+ User->getOperand(0).getValueType()));
} else if (User->getOpcode() == ISD::SELECT_CC) {
- if (User->getOperand(0) == PromOps[i] ||
- User->getOperand(1) == PromOps[i])
- return SDValue();
+ if (User->getOperand(0) == PromOps[i])
+ SelectTruncOp[0].insert(std::make_pair(User,
+ User->getOperand(0).getValueType()));
+ if (User->getOperand(1) == PromOps[i])
+ SelectTruncOp[1].insert(std::make_pair(User,
+ User->getOperand(1).getValueType()));
}
}
}
@@ -8257,6 +8263,19 @@ SDValue PPCTargetLowering::DAGCombineExt
continue;
}
+ // For SELECT and SELECT_CC nodes, we do a similar check for any
+ // to-be-promoted comparison inputs.
+ if (PromOp.getOpcode() == ISD::SELECT ||
+ PromOp.getOpcode() == ISD::SELECT_CC) {
+ if ((SelectTruncOp[0].count(PromOp.getNode()) &&
+ PromOp.getOperand(0).getValueType() != N->getValueType(0)) ||
+ (SelectTruncOp[1].count(PromOp.getNode()) &&
+ PromOp.getOperand(1).getValueType() != N->getValueType(0))) {
+ PromOps.insert(PromOps.begin(), PromOp);
+ continue;
+ }
+ }
+
SmallVector<SDValue, 3> Ops(PromOp.getNode()->op_begin(),
PromOp.getNode()->op_end());
@@ -8275,6 +8294,18 @@ SDValue PPCTargetLowering::DAGCombineExt
Ops[C+i] = DAG.getAnyExtOrTrunc(Ops[C+i], dl, N->getValueType(0));
}
+ // If we've promoted the comparison inputs of a SELECT or SELECT_CC,
+ // truncate them again to the original value type.
+ if (PromOp.getOpcode() == ISD::SELECT ||
+ PromOp.getOpcode() == ISD::SELECT_CC) {
+ auto SI0 = SelectTruncOp[0].find(PromOp.getNode());
+ if (SI0 != SelectTruncOp[0].end())
+ Ops[0] = DAG.getNode(ISD::TRUNCATE, dl, SI0->second, Ops[0]);
+ auto SI1 = SelectTruncOp[1].find(PromOp.getNode());
+ if (SI1 != SelectTruncOp[1].end())
+ Ops[1] = DAG.getNode(ISD::TRUNCATE, dl, SI1->second, Ops[1]);
+ }
+
DAG.ReplaceAllUsesOfValueWith(PromOp,
DAG.getNode(PromOp.getOpcode(), dl, N->getValueType(0), Ops));
}
Modified: llvm/trunk/test/CodeGen/PowerPC/rm-zext.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/rm-zext.ll?rev=224213&r1=224212&r2=224213&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/PowerPC/rm-zext.ll (original)
+++ llvm/trunk/test/CodeGen/PowerPC/rm-zext.ll Sat Dec 13 23:53:19 2014
@@ -28,5 +28,16 @@ entry:
; CHECK: blr
}
+define zeroext i32 @min(i32 zeroext %a, i32 zeroext %b) #0 {
+entry:
+ %cmp = icmp ule i32 %a, %b
+ %cond = select i1 %cmp, i32 %a, i32 %b
+ ret i32 %cond
+
+; CHECK-LABEL @min
+; CHECK-NOT: rldicl 3, {{[0-9]+}}, 0, 32
+; CHECK: blr
+}
+
attributes #0 = { nounwind readnone }
More information about the llvm-commits
mailing list