when we know the signbit of an input to uint_to_fp is zero,
change it to sint_to_fp on targets where that is cheaper (and
visaversa of course). This allows us to compile uint_to_fp to:
_test:
movl 4(%esp), %eax
shrl $23, %eax
cvtsi2ss %eax, %xmm0
movl 8(%esp), %eax
movss %xmm0, (%eax)
ret
instead of:
.align 3
LCPI1_0: ## double
.long 0 ## double least significant word 4.5036e+15
.long 1127219200 ## double most significant word 4.5036e+15
.text
.align 4,0x90
.globl _test
_test:
subl $12, %esp
movl 16(%esp), %eax
shrl $23, %eax
movl %eax, (%esp)
movl $1127219200, 4(%esp)
movsd (%esp), %xmm0
subsd LCPI1_0, %xmm0
cvtsd2ss %xmm0, %xmm0
movl 20(%esp), %eax
movss %xmm0, (%eax)
addl $12, %esp
ret
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52747 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index c07ad27..d39d43e 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3844,10 +3844,22 @@
SDOperand N0 = N->getOperand(0);
ConstantSDNode *N0C = dyn_cast<ConstantSDNode>(N0);
MVT VT = N->getValueType(0);
-
+ MVT OpVT = N0.getValueType();
+
// fold (sint_to_fp c1) -> c1fp
- if (N0C && N0.getValueType() != MVT::ppcf128)
+ if (N0C && OpVT != MVT::ppcf128)
return DAG.getNode(ISD::SINT_TO_FP, VT, N0);
+
+ // If the input is a legal type, and SINT_TO_FP is not legal on this target,
+ // but UINT_TO_FP is legal on this target, try to convert.
+ if (TLI.isTypeLegal(OpVT) && !TLI.isOperationLegal(ISD::SINT_TO_FP, OpVT) &&
+ TLI.isOperationLegal(ISD::UINT_TO_FP, OpVT)) {
+ // If the sign bit is known to be zero, we can change this to UINT_TO_FP.
+ if (DAG.SignBitIsZero(N0))
+ return DAG.getNode(ISD::UINT_TO_FP, VT, N0);
+ }
+
+
return SDOperand();
}
@@ -3855,10 +3867,21 @@
SDOperand N0 = N->getOperand(0);
ConstantSDNode *N0C = dyn_cast<ConstantSDNode>(N0);
MVT VT = N->getValueType(0);
+ MVT OpVT = N0.getValueType();
// fold (uint_to_fp c1) -> c1fp
- if (N0C && N0.getValueType() != MVT::ppcf128)
+ if (N0C && OpVT != MVT::ppcf128)
return DAG.getNode(ISD::UINT_TO_FP, VT, N0);
+
+ // If the input is a legal type, and UINT_TO_FP is not legal on this target,
+ // but SINT_TO_FP is legal on this target, try to convert.
+ if (TLI.isTypeLegal(OpVT) && !TLI.isOperationLegal(ISD::UINT_TO_FP, OpVT) &&
+ TLI.isOperationLegal(ISD::SINT_TO_FP, OpVT)) {
+ // If the sign bit is known to be zero, we can change this to SINT_TO_FP.
+ if (DAG.SignBitIsZero(N0))
+ return DAG.getNode(ISD::SINT_TO_FP, VT, N0);
+ }
+
return SDOperand();
}