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Fix constant folding through bitcasts by no longer relying on undefined behaviour (converting NaN values between float and double).

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SelectionDAG::getConstantFP(double Val, EVT VT, bool isTarget);
should not be used when Val is not a simple constant (as the comment in
SelectionDAG.h indicates). This patch avoids using this function
when folding an unknown constant through a bitcast, where it cannot be
guaranteed that Val will be a simple constant.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163703 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Kristof Beyls 2012-09-12 11:25:02 +00:00
parent d76f6eadc8
commit 789efbad2a
2 changed files with 12 additions and 2 deletions
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4
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -2454,9 +2454,9 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL,
}
case ISD::BITCAST:
if (VT == MVT::f32 && C->getValueType(0) == MVT::i32)
return getConstantFP(Val.bitsToFloat(), VT);
return getConstantFP(APFloat(Val), VT);
else if (VT == MVT::f64 && C->getValueType(0) == MVT::i64)
return getConstantFP(Val.bitsToDouble(), VT);
return getConstantFP(APFloat(Val), VT);
break;
case ISD::BSWAP:
return getConstant(Val.byteSwap(), VT);

10
test/CodeGen/ARM/constants.ll
View File

@ -45,6 +45,16 @@ r:
ret void
}
define i32 @f8() nounwind {
; Check that constant propagation through (i32)-1 => (float)Nan => (i32)-1
; gives expected result
; CHECK: f8
; CHECK: mvn r0, #0
%tmp0 = bitcast i32 -1 to float
%tmp1 = bitcast float %tmp0 to i32
ret i32 %tmp1
}
%t1 = type { <3 x float>, <3 x float> }
@const1 = global %t1 { <3 x float> zeroinitializer,