diff options
| -rw-r--r-- | lib/CodeGen/SelectionDAG/TargetLowering.cpp | 22 | ||||
| -rw-r--r-- | lib/Target/X86/README.txt | 17 | ||||
| -rw-r--r-- | test/CodeGen/X86/isnan.ll | 11 |
3 files changed, 33 insertions, 17 deletions
diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp index eb08bba..ad33273 100644 --- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp +++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp @@ -1280,6 +1280,28 @@ TargetLowering::SimplifySetCC(MVT::ValueType VT, SDOperand N0, SDOperand N1, // Constant fold or commute setcc. SDOperand O = DAG.FoldSetCC(VT, N0, N1, Cond); if (O.Val) return O; + } else if (ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(N1.Val)) { + // If the RHS of an FP comparison is a constant, simplify it away in + // some cases. + if (CFP->getValueAPF().isNaN()) { + // If an operand is known to be a nan, we can fold it. + switch (ISD::getUnorderedFlavor(Cond)) { + default: assert(0 && "Unknown flavor!"); + case 0: // Known false. + return DAG.getConstant(0, VT); + case 1: // Known true. + return DAG.getConstant(1, VT); + case 2: // undefind. + return DAG.getNode(ISD::UNDEF, VT); + } + } + + // Otherwise, we know the RHS is not a NaN. Simplify the node to drop the + // constant if knowing that the operand is non-nan is enough. We prefer to + // have SETO(x,x) instead of SETO(x, 0.0) because this avoids having to + // materialize 0.0. + if (Cond == ISD::SETO || Cond == ISD::SETUO) + return DAG.getSetCC(VT, N0, N0, Cond); } if (N0 == N1) { diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt index 08b5875..759c7ac 100644 --- a/lib/Target/X86/README.txt +++ b/lib/Target/X86/README.txt @@ -816,23 +816,6 @@ _add_zf: //===---------------------------------------------------------------------===// -This: -#include <math.h> -int foo(double X) { return isnan(X); } - -compiles to (-m64): - -_foo: - pxor %xmm1, %xmm1 - ucomisd %xmm1, %xmm0 - setp %al - movzbl %al, %eax - ret - -the pxor is not needed, we could compare the value against itself. - -//===---------------------------------------------------------------------===// - These two functions have identical effects: unsigned int f(unsigned int i, unsigned int n) {++i; if (i == n) ++i; return i;} diff --git a/test/CodeGen/X86/isnan.ll b/test/CodeGen/X86/isnan.ll new file mode 100644 index 0000000..18fe29a --- /dev/null +++ b/test/CodeGen/X86/isnan.ll @@ -0,0 +1,11 @@ +; RUN: llvm-as < %s | llc -march=x86 -mcpu=yonah | not grep pxor + +; This should not need to materialize 0.0 to evaluate the condition. + +define i32 @test(double %X) nounwind { +entry: + %tmp6 = fcmp uno double %X, 0.000000e+00 ; <i1> [#uses=1] + %tmp67 = zext i1 %tmp6 to i32 ; <i32> [#uses=1] + ret i32 %tmp67 +} + |