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Implement rdar://7415680 - Twine integer support lacks greatness

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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.




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103107 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner committed 2010-05-05 18:40:33 +00:00
1 parent 15cdda259a
commit ea03e10fac
2 files changed
+12 -11
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lib/Support/Twine.cpp
+4 -4
View File
@@ -48,10 +48,10 @@ void Twine::printOneChild(raw_ostream &OS, const void *Ptr,
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 @@ void Twine::printOneChildRepr(raw_ostream &OS, const void *Ptr,
<< 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) << "\"";