diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp index e11522db79e..df86064d282 100644 --- a/lib/Target/X86/X86ISelLowering.cpp +++ b/lib/Target/X86/X86ISelLowering.cpp @@ -10074,10 +10074,27 @@ SDValue X86TargetLowering::EmitTest(SDValue Op, unsigned X86CC, SDLoc dl, break; case X86::COND_G: case X86::COND_GE: case X86::COND_L: case X86::COND_LE: - case X86::COND_O: case X86::COND_NO: - NeedOF = true; + case X86::COND_O: case X86::COND_NO: { + // Check if we really need to set the + // Overflow flag. If NoSignedWrap is present + // that is not actually needed. + switch (Op->getOpcode()) { + case ISD::ADD: + case ISD::SUB: + case ISD::MUL: + case ISD::SHL: { + const BinaryWithFlagsSDNode *BinNode = + cast(Op.getNode()); + if (BinNode->hasNoSignedWrap()) + break; + } + default: + NeedOF = true; + break; + } break; } + } // See if we can use the EFLAGS value from the operand instead of // doing a separate TEST. TEST always sets OF and CF to 0, so unless // we prove that the arithmetic won't overflow, we can't use OF or CF. diff --git a/test/CodeGen/X86/2014-05-29-factorial.ll b/test/CodeGen/X86/2014-05-29-factorial.ll new file mode 100644 index 00000000000..70255bd3219 --- /dev/null +++ b/test/CodeGen/X86/2014-05-29-factorial.ll @@ -0,0 +1,24 @@ +; RUN: llc < %s -march=x86-64 | FileCheck %s +; CHECK: decq %rdi +; CHECK-NOT: testq %rdi, %rdi + +define i64 @fact2(i64 %x) { +entry: + br label %while.body + +while.body: + %result.06 = phi i64 [ %mul, %while.body ], [ 1, %entry ] + %x.addr.05 = phi i64 [ %dec, %while.body ], [ %x, %entry ] + %mul = mul nsw i64 %result.06, %x.addr.05 + %dec = add nsw i64 %x.addr.05, -1 + %cmp = icmp sgt i64 %dec, 0 + br i1 %cmp, label %while.body, label %while.end.loopexit + +while.end.loopexit: + %mul.lcssa = phi i64 [ %mul, %while.body ] + br label %while.end + +while.end: + %result.0.lcssa = phi i64 [ %mul.lcssa, %while.end.loopexit ] + ret i64 %result.0.lcssa +}