Add a -disable-16bit flag and associated support for experimenting with
disabling the use of 16-bit operations on x86. This doesn't yet work for
inline asms with 16-bit constraints, vectors with 16-bit elements,
trampoline code, and perhaps other obscurities, but it's enough to try
some experiments.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80930 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index c0999f5..6ada5da 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -47,6 +47,14 @@
static cl::opt<bool>
DisableMMX("disable-mmx", cl::Hidden, cl::desc("Disable use of MMX"));
+// Disable16Bit - 16-bit operations typically have a larger encoding than
+// corresponding 32-bit instructions, and 16-bit code is slow on some
+// processors. This is an experimental flag to disable 16-bit operations
+// (which forces them to be Legalized to 32-bit operations).
+static cl::opt<bool>
+Disable16Bit("disable-16bit", cl::Hidden,
+ cl::desc("Disable use of 16-bit instructions"));
+
// Forward declarations.
static SDValue getMOVL(SelectionDAG &DAG, DebugLoc dl, EVT VT, SDValue V1,
SDValue V2);
@@ -99,7 +107,8 @@
// Set up the register classes.
addRegisterClass(MVT::i8, X86::GR8RegisterClass);
- addRegisterClass(MVT::i16, X86::GR16RegisterClass);
+ if (!Disable16Bit)
+ addRegisterClass(MVT::i16, X86::GR16RegisterClass);
addRegisterClass(MVT::i32, X86::GR32RegisterClass);
if (Subtarget->is64Bit())
addRegisterClass(MVT::i64, X86::GR64RegisterClass);
@@ -108,9 +117,11 @@
// We don't accept any truncstore of integer registers.
setTruncStoreAction(MVT::i64, MVT::i32, Expand);
- setTruncStoreAction(MVT::i64, MVT::i16, Expand);
+ if (!Disable16Bit)
+ setTruncStoreAction(MVT::i64, MVT::i16, Expand);
setTruncStoreAction(MVT::i64, MVT::i8 , Expand);
- setTruncStoreAction(MVT::i32, MVT::i16, Expand);
+ if (!Disable16Bit)
+ setTruncStoreAction(MVT::i32, MVT::i16, Expand);
setTruncStoreAction(MVT::i32, MVT::i8 , Expand);
setTruncStoreAction(MVT::i16, MVT::i8, Expand);
@@ -261,8 +272,13 @@
setOperationAction(ISD::CTTZ , MVT::i8 , Custom);
setOperationAction(ISD::CTLZ , MVT::i8 , Custom);
setOperationAction(ISD::CTPOP , MVT::i16 , Expand);
- setOperationAction(ISD::CTTZ , MVT::i16 , Custom);
- setOperationAction(ISD::CTLZ , MVT::i16 , Custom);
+ if (Disable16Bit) {
+ setOperationAction(ISD::CTTZ , MVT::i16 , Expand);
+ setOperationAction(ISD::CTLZ , MVT::i16 , Expand);
+ } else {
+ setOperationAction(ISD::CTTZ , MVT::i16 , Custom);
+ setOperationAction(ISD::CTLZ , MVT::i16 , Custom);
+ }
setOperationAction(ISD::CTPOP , MVT::i32 , Expand);
setOperationAction(ISD::CTTZ , MVT::i32 , Custom);
setOperationAction(ISD::CTLZ , MVT::i32 , Custom);
@@ -279,13 +295,19 @@
setOperationAction(ISD::SELECT , MVT::i1 , Promote);
// X86 wants to expand cmov itself.
setOperationAction(ISD::SELECT , MVT::i8 , Custom);
- setOperationAction(ISD::SELECT , MVT::i16 , Custom);
+ if (Disable16Bit)
+ setOperationAction(ISD::SELECT , MVT::i16 , Expand);
+ else
+ setOperationAction(ISD::SELECT , MVT::i16 , Custom);
setOperationAction(ISD::SELECT , MVT::i32 , Custom);
setOperationAction(ISD::SELECT , MVT::f32 , Custom);
setOperationAction(ISD::SELECT , MVT::f64 , Custom);
setOperationAction(ISD::SELECT , MVT::f80 , Custom);
setOperationAction(ISD::SETCC , MVT::i8 , Custom);
- setOperationAction(ISD::SETCC , MVT::i16 , Custom);
+ if (Disable16Bit)
+ setOperationAction(ISD::SETCC , MVT::i16 , Expand);
+ else
+ setOperationAction(ISD::SETCC , MVT::i16 , Custom);
setOperationAction(ISD::SETCC , MVT::i32 , Custom);
setOperationAction(ISD::SETCC , MVT::f32 , Custom);
setOperationAction(ISD::SETCC , MVT::f64 , Custom);
@@ -1085,7 +1107,7 @@
SmallVector<SDValue, 6> RetOps;
RetOps.push_back(Chain); // Operand #0 = Chain (updated below)
// Operand #1 = Bytes To Pop
- RetOps.push_back(DAG.getConstant(getBytesToPopOnReturn(), MVT::i16));
+ RetOps.push_back(DAG.getTargetConstant(getBytesToPopOnReturn(), MVT::i16));
// Copy the result values into the output registers.
for (unsigned i = 0; i != RVLocs.size(); ++i) {