The library call simplifier folds memcmp calls with all constant arguments
to a constant. For example:
memcmp("foo", "foo", 3) -> 0
memcmp("hel", "foo", 3) -> 1
memcmp("foo", "hel", 3) -> -1
The folding is implemented in terms of the system memcmp that LLVM gets
linked with. It currently just blindly uses the value returned from
the system memcmp as the folded constant.
This patch normalizes the values returned from the system memcmp to
(-1, 0, 1) so that we get consistent results across multiple platforms.
The test cases were adjusted accordingly.
llvm-svn: 167726
Transforms/InstCombine/memcmp-1.ll has a test case that looks like:
@foo = constant [4 x i8] c"foo\00"
@hel = constant [4 x i8] c"hel\00"
...
%mem1 = getelementptr [4 x i8]* @hel, i32 0, i32 0
%mem2 = getelementptr [4 x i8]* @foo, i32 0, i32 0
%ret = call i32 @memcmp(i8* %mem1, i8* %mem2, i32 3)
ret i32 %ret
; CHECK: ret i32 2
The folded return value (2 above) is computed using the system memcmp
that the compiler is linked with. This can return different values on
different systems. The test was originally written on an OS X 10.7.5
x86-64 box and passed. However, it failed on one of the x86-64 FreeBSD
buildbots because the system memcpy on that machine returned a different
value (1 instead of 2).
I fixed the test by checking the folding constants with regexes.
llvm-svn: 167691
Several of the simplifiers migrated from the simplify-libcalls pass to
the instcombine pass were not correctly checking the target library
information to gate the simplifications. This patch ensures that the
check is made.
llvm-svn: 167660
getIntPtrType support for multiple address spaces via a pointer type,
and also introduced a crasher bug in the constant folder reported in
PR14233.
These commits also contained several problems that should really be
addressed before they are re-committed. I have avoided reverting various
cleanups to the DataLayout APIs that are reasonable to have moving
forward in order to reduce the amount of churn, and minimize the number
of commits that were reverted. I've also manually updated merge
conflicts and manually arranged for the getIntPtrType function to stay
in DataLayout and to be defined in a plausible way after this revert.
Thanks to Duncan for working through this exact strategy with me, and
Nick Lewycky for tracking down the really annoying crasher this
triggered. (Test case to follow in its own commit.)
After discussing with Duncan extensively, and based on a note from
Micah, I'm going to continue to back out some more of the more
problematic patches in this series in order to ensure we go into the
LLVM 3.2 branch with a reasonable story here. I'll send a note to
llvmdev explaining what's going on and why.
Summary of reverted revisions:
r166634: Fix a compiler warning with an unused variable.
r166607: Add some cleanup to the DataLayout changes requested by
Chandler.
r166596: Revert "Back out r166591, not sure why this made it through
since I cancelled the command. Bleh, sorry about this!
r166591: Delete a directory that wasn't supposed to be checked in yet.
r166578: Add in support for getIntPtrType to get the pointer type based
on the address space.
llvm-svn: 167221
This patch migrates the stpcpy optimizations from the simplify-libcalls
pass into the instcombine library call simplifier. Note that the
__stpcpy_chk simplifications were migrated in a previous commit.
llvm-svn: 167083
r166198 migrated the strcpy optimization to instcombine. The strcpy
simplifier that was migrated from Transforms/Scalar/SimplifyLibCalls.cpp
was also doing some __strcpy_chk simplifications. Those fortified
simplifications were migrated as well, but introduced a bug in the
__stpcpy_chk simplifier in the process. This happened because the
__strcpy_chk and __stpcpy_chk simplifiers were both mapped to StrCpyChkOpt
which was updated with simplifications that worked for __strcpy_chk, but
not __stpcpy_chk.
This patch fixes the problem by adding proper test coverage and creating a
new simplifier for __stpcpy_chk (instead of sharing one with __strcpy_chk).
llvm-svn: 167082
%V = mul i64 %N, 4
%t = getelementptr i8* bitcast (i32* %arr to i8*), i32 %V
into
%t1 = getelementptr i32* %arr, i32 %N
%t = bitcast i32* %t1 to i8*
incorporating the multiplication into the getelementptr.
This happens all the time in dragonegg, for example for
int foo(int *A, int N) {
return A[N];
}
because gcc turns this into byte pointer arithmetic before it hits the plugin:
D.1590_2 = (long unsigned int) N_1(D);
D.1591_3 = D.1590_2 * 4;
D.1592_5 = A_4(D) + D.1591_3;
D.1589_6 = *D.1592_5;
return D.1589_6;
The D.1592_5 line is a POINTER_PLUS_EXPR, which is turned into a getelementptr
on a bitcast of A_4 to i8*, so this becomes exactly the kind of IR that the
transform fires on.
An analogous transform (with no testcases!) already existed for bitcasts of
arrays, so I rewrote it to share code with this one.
llvm-svn: 166474
This patch migrates the strcpy optimizations from the simplify-libcalls pass
into the instcombine library call simplifier. Note also that StrCpyChkOpt
has been updated with a few simplifications that were being done in the
simplify-libcalls version of StrCpyOpt, but not in the migrated implementation
of StrCpyOpt. There is no reason to overload StrCpyOpt with fortified and
regular simplifications in the new model since there is already a dedicated
simplifier for __strcpy_chk.
llvm-svn: 166198
An obfuscated splat is where the frontend poorly generates code for a splat
using several different shuffles to create the splat, i.e.,
%A = load <4 x float>* %in_ptr, align 16
%B = shufflevector <4 x float> %A, <4 x float> undef, <4 x i32> <i32 0, i32 0, i32 undef, i32 undef>
%C = shufflevector <4 x float> %B, <4 x float> %A, <4 x i32> <i32 0, i32 1, i32 4, i32 undef>
%D = shufflevector <4 x float> %C, <4 x float> %A, <4 x i32> <i32 0, i32 1, i32 2, i32 4>
llvm-svn: 166061
This patch migrates the strcmp and strncmp optimizations from the
simplify-libcalls pass into the instcombine library call simplifier.
llvm-svn: 165915
This patch migrates the strchr and strrchr optimizations from the
simplify-libcalls pass into the instcombine library call simplifier.
llvm-svn: 165875
This patch migrates the strcat and strncat optimizations from the
simplify-libcalls pass into the instcombine library call simplifier.
llvm-svn: 165874
