Generate ftst instructions for comparison against zero
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11098 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelSimple.cpp b/lib/Target/X86/X86ISelSimple.cpp
index abfcad1..45df829 100644
--- a/lib/Target/X86/X86ISelSimple.cpp
+++ b/lib/Target/X86/X86ISelSimple.cpp
@@ -702,6 +702,15 @@
return OpNum;
}
+ // Special case handling of comparison against +/- 0.0
+ if (ConstantFP *CFP = dyn_cast<ConstantFP>(Op1))
+ if (CFP->isExactlyValue(+0.0) || CFP->isExactlyValue(-0.0)) {
+ BMI(MBB, IP, X86::FTST, 1).addReg(Op0r);
+ BMI(MBB, IP, X86::FNSTSWr8, 0);
+ BMI(MBB, IP, X86::SAHF, 1);
+ return OpNum;
+ }
+
unsigned Op1r = getReg(Op1, MBB, IP);
switch (Class) {
default: assert(0 && "Unknown type class!");