[llvmgcc] C front-end does not emit 'zeroinitializer' when possible

[lattner]

Bugzilla Link	205
Resolution	FIXED
Resolved on	Feb 22, 2010 12:50
Version	1.0
OS	All

Extended Description

This is strictly a quality-of-implementation bug, but it does slow down the
C/C++ compiler needlessly.

In particular, the C front-end emits a .ll file containing an explicit list of
all of the zeros in cases like this:

---

int test[10000];

Instead, it would make the C front-end more efficient and the gccas tool parse
the result faster if it just emitted the zeroinitializer token.

-Chris

[lattner]

assigned to @lattner

[lattner]

Fixed. Testcase here:
Regression/CFrontend/2004-02-14-ZeroInitializer.c.tr

Patch here:
http://mail.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20040209/011695.html

-Chris

[lattner]

Here's another patch that helps:
http://mail.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20040209/011697.html

It is worth noting that fixing this bug allows us to reduce the size of
129.compress/harness.ll from 391M to 137K. This puts a LOT less pressure on the
.ll file parser. :)

-Chris