Implement rdar://7415680 - Twine integer support lacks greatness
Microoptimize Twine's with unsigned and int to not pin their value to
the stack. This saves stack space in common cases and allows mem2reg
in the caller. A simple example is:
void foo(const Twine &);
void bar(int x) {
foo("xyz: " + Twine(x));
}
Before:
__Z3bari:
subq $40, %rsp
movl %edi, 36(%rsp)
leaq L_.str3(%rip), %rax
leaq 36(%rsp), %rcx
leaq 8(%rsp), %rdi
movq %rax, 8(%rsp)
movq %rcx, 16(%rsp)
movb $3, 24(%rsp)
movb $7, 25(%rsp)
callq __Z3fooRKN4llvm5TwineE
addq $40, %rsp
ret
After:
__Z3bari:
subq $24, %rsp
leaq L_.str3(%rip), %rax
movq %rax, (%rsp)
movslq %edi, %rax
movq %rax, 8(%rsp)
movb $3, 16(%rsp)
movb $7, 17(%rsp)
leaq (%rsp), %rdi
callq __Z3fooRKN4llvm5TwineE
addq $24, %rsp
ret
It saves 16 bytes of stack and one instruction in this case.
llvm-svn: 103107
diff --git a/llvm/include/llvm/ADT/Twine.h b/llvm/include/llvm/ADT/Twine.h
index 97e9df4..b519a3e 100644
--- a/llvm/include/llvm/ADT/Twine.h
+++ b/llvm/include/llvm/ADT/Twine.h
@@ -99,11 +99,12 @@
/// A pointer to a StringRef instance.
StringRefKind,
- /// A pointer to an unsigned int value, to render as an unsigned decimal
- /// integer.
+ /// An unsigned int value reinterpreted as a pointer, to render as an
+ /// unsigned decimal integer.
DecUIKind,
- /// A pointer to an int value, to render as a signed decimal integer.
+ /// An int value reinterpreted as a pointer, to render as a signed
+ /// decimal integer.
DecIKind,
/// A pointer to an unsigned long value, to render as an unsigned decimal
@@ -259,13 +260,13 @@
}
/// Construct a twine to print \arg Val as an unsigned decimal integer.
- explicit Twine(const unsigned int &Val)
- : LHS(&Val), LHSKind(DecUIKind), RHSKind(EmptyKind) {
+ explicit Twine(unsigned Val)
+ : LHS((void*)(intptr_t)Val), LHSKind(DecUIKind), RHSKind(EmptyKind) {
}
/// Construct a twine to print \arg Val as a signed decimal integer.
- explicit Twine(const int &Val)
- : LHS(&Val), LHSKind(DecIKind), RHSKind(EmptyKind) {
+ explicit Twine(int Val)
+ : LHS((void*)(intptr_t)Val), LHSKind(DecIKind), RHSKind(EmptyKind) {
}
/// Construct a twine to print \arg Val as an unsigned decimal integer.
diff --git a/llvm/lib/Support/Twine.cpp b/llvm/lib/Support/Twine.cpp
index 21504e9..b3ea013 100644
--- a/llvm/lib/Support/Twine.cpp
+++ b/llvm/lib/Support/Twine.cpp
@@ -48,10 +48,10 @@
OS << *static_cast<const StringRef*>(Ptr);
break;
case Twine::DecUIKind:
- OS << *static_cast<const unsigned int*>(Ptr);
+ OS << (unsigned)(uintptr_t)Ptr;
break;
case Twine::DecIKind:
- OS << *static_cast<const int*>(Ptr);
+ OS << (int)(intptr_t)Ptr;
break;
case Twine::DecULKind:
OS << *static_cast<const unsigned long*>(Ptr);
@@ -95,10 +95,10 @@
<< static_cast<const StringRef*>(Ptr) << "\"";
break;
case Twine::DecUIKind:
- OS << "decUI:\"" << *static_cast<const unsigned int*>(Ptr) << "\"";
+ OS << "decUI:\"" << (unsigned)(uintptr_t)Ptr << "\"";
break;
case Twine::DecIKind:
- OS << "decI:\"" << *static_cast<const int*>(Ptr) << "\"";
+ OS << "decI:\"" << (int)(intptr_t)Ptr << "\"";
break;
case Twine::DecULKind:
OS << "decUL:\"" << *static_cast<const unsigned long*>(Ptr) << "\"";