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authorBill Wendling <isanbard@gmail.com>2011-09-18 12:51:05 +0000
committerBill Wendling <isanbard@gmail.com>2011-09-18 12:51:05 +0000
commit88816ec96349466c8012ab1f70f8e01a7af556ce (patch)
tree9f9dbb18889cae14015716cad8f2d57b443c4ace /docs
parentea55c83e7f6e3a9b1081902ca50a4e12224894c0 (diff)
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Fix up the formating and change llvm-gcc to clang.
Note that this example doesn't work anymore! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139999 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs')
-rw-r--r--docs/LinkTimeOptimization.html57
1 files changed, 32 insertions, 25 deletions
diff --git a/docs/LinkTimeOptimization.html b/docs/LinkTimeOptimization.html
index b3bc4814fd..52ab119707 100644
--- a/docs/LinkTimeOptimization.html
+++ b/docs/LinkTimeOptimization.html
@@ -79,7 +79,7 @@ conservative escape analysis.
<p>The following example illustrates the advantages of LTO's integrated
approach and clean interface. This example requires a system linker which
supports LTO through the interface described in this document. Here,
- llvm-gcc transparently invokes system linker. </p>
+ clang transparently invokes system linker. </p>
<ul>
<li> Input source file <tt>a.c</tt> is compiled into LLVM bitcode form.
<li> Input source file <tt>main.c</tt> is compiled into native object code.
@@ -89,27 +89,29 @@ conservative escape analysis.
extern int foo1(void);
extern void foo2(void);
extern void foo4(void);
+
--- a.c ---
#include "a.h"
static signed int i = 0;
void foo2(void) {
- i = -1;
+ i = -1;
}
static int foo3() {
-foo4();
-return 10;
+ foo4();
+ return 10;
}
int foo1(void) {
-int data = 0;
+ int data = 0;
-if (i &lt; 0) { data = foo3(); }
+ if (i &lt; 0)
+ data = foo3();
-data = data + 42;
-return data;
+ data = data + 42;
+ return data;
}
--- main.c ---
@@ -117,30 +119,35 @@ return data;
#include "a.h"
void foo4(void) {
- printf ("Hi\n");
+ printf("Hi\n");
}
int main() {
- return foo1();
+ return foo1();
}
--- command lines ---
-$ llvm-gcc --emit-llvm -c a.c -o a.o # &lt;-- a.o is LLVM bitcode file
-$ llvm-gcc -c main.c -o main.o # &lt;-- main.o is native object file
-$ llvm-gcc a.o main.o -o main # &lt;-- standard link command without any modifications
+$ clang -emit-llvm -c a.c -o a.o # &lt;-- a.o is LLVM bitcode file
+$ clang -c main.c -o main.o # &lt;-- main.o is native object file
+$ clang a.o main.o -o main # &lt;-- standard link command without any modifications
</pre>
- <p>In this example, the linker recognizes that <tt>foo2()</tt> is an
- externally visible symbol defined in LLVM bitcode file. The linker completes
- its usual symbol resolution
- pass and finds that <tt>foo2()</tt> is not used anywhere. This information
- is used by the LLVM optimizer and it removes <tt>foo2()</tt>. As soon as
- <tt>foo2()</tt> is removed, the optimizer recognizes that condition
- <tt>i &lt; 0</tt> is always false, which means <tt>foo3()</tt> is never
- used. Hence, the optimizer removes <tt>foo3()</tt>, also. And this in turn,
- enables linker to remove <tt>foo4()</tt>. This example illustrates the
- advantage of tight integration with the linker. Here, the optimizer can not
- remove <tt>foo3()</tt> without the linker's input.
- </p>
+
+<ul>
+ <li>In this example, the linker recognizes that <tt>foo2()</tt> is an
+ externally visible symbol defined in LLVM bitcode file. The linker
+ completes its usual symbol resolution pass and finds that <tt>foo2()</tt>
+ is not used anywhere. This information is used by the LLVM optimizer and
+ it removes <tt>foo2()</tt>.</li>
+ <li>As soon as <tt>foo2()</tt> is removed, the optimizer recognizes that condition
+ <tt>i &lt; 0</tt> is always false, which means <tt>foo3()</tt> is never
+ used. Hence, the optimizer also removes <tt>foo3()</tt>.</li>
+ <li>And this in turn, enables linker to remove <tt>foo4()</tt>.</li>
+</ul>
+
+<p>This example illustrates the advantage of tight integration with the
+ linker. Here, the optimizer can not remove <tt>foo3()</tt> without the
+ linker's input.</p>
+
</div>
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