Fix a minor code-quality issue. When passing 8 and 16-bit integer constants
to function calls, we would emit dead code, like this:
int Y(int, short, double);
int X() {
Y(4, 123, 4);
}
--- Old
X:
sub %ESP, 20
mov %EAX, 4
mov DWORD PTR [%ESP], %EAX
*** mov %AX, 123
mov %AX, 123
movsx %EAX, %AX
mov DWORD PTR [%ESP + 4], %EAX
fld QWORD PTR [.CPIX_0]
fstp QWORD PTR [%ESP + 8]
call Y
mov %EAX, 0
# IMPLICIT_USE %EAX %ESP
add %ESP, 20
ret
Now we emit:
X:
sub %ESP, 20
mov %EAX, 4
mov DWORD PTR [%ESP], %EAX
mov %AX, 123
movsx %EAX, %AX
mov DWORD PTR [%ESP + 4], %EAX
fld QWORD PTR [.CPIX_0]
fstp QWORD PTR [%ESP + 8]
call Y
mov %EAX, 0
# IMPLICIT_USE %EAX %ESP
add %ESP, 20
ret
Next up, eliminate the mov AX and movsx entirely!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12026 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/InstSelectSimple.cpp b/lib/Target/X86/InstSelectSimple.cpp
index 0aa4ef9..b779664 100644
--- a/lib/Target/X86/InstSelectSimple.cpp
+++ b/lib/Target/X86/InstSelectSimple.cpp
@@ -1098,7 +1098,7 @@
// Arguments go on the stack in reverse order, as specified by the ABI.
unsigned ArgOffset = 0;
for (unsigned i = 0, e = Args.size(); i != e; ++i) {
- unsigned ArgReg = Args[i].Val ? getReg(Args[i].Val) : Args[i].Reg;
+ unsigned ArgReg;
switch (getClassB(Args[i].Ty)) {
case cByte:
case cShort: {
@@ -1110,10 +1110,12 @@
break;
}
case cInt:
+ ArgReg = Args[i].Val ? getReg(Args[i].Val) : Args[i].Reg;
addRegOffset(BuildMI(BB, X86::MOV32mr, 5),
X86::ESP, ArgOffset).addReg(ArgReg);
break;
case cLong:
+ ArgReg = Args[i].Val ? getReg(Args[i].Val) : Args[i].Reg;
addRegOffset(BuildMI(BB, X86::MOV32mr, 5),
X86::ESP, ArgOffset).addReg(ArgReg);
addRegOffset(BuildMI(BB, X86::MOV32mr, 5),
@@ -1122,6 +1124,7 @@
break;
case cFP:
+ ArgReg = Args[i].Val ? getReg(Args[i].Val) : Args[i].Reg;
if (Args[i].Ty == Type::FloatTy) {
addRegOffset(BuildMI(BB, X86::FST32m, 5),
X86::ESP, ArgOffset).addReg(ArgReg);