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author | Duncan Sands <baldrick@free.fr> | 2011-01-18 09:24:58 +0000 |
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committer | Duncan Sands <baldrick@free.fr> | 2011-01-18 09:24:58 +0000 |
commit | fe02c69f84ad52d42be934e4fe702f03e4991a6a (patch) | |
tree | aa3ac73de8b775633dc315afb6b202b8ed74770e /test/Transforms/InstSimplify/2010-12-20-Distribute.ll | |
parent | 908d8e82b5cc19d1a0a55a5fbc9dfd87359d726e (diff) | |
download | llvm-fe02c69f84ad52d42be934e4fe702f03e4991a6a.tar.gz llvm-fe02c69f84ad52d42be934e4fe702f03e4991a6a.tar.bz2 llvm-fe02c69f84ad52d42be934e4fe702f03e4991a6a.tar.xz |
Simplify (X<<1)-X into X. According to my auto-simplier this is the most common missed
simplification in fully optimized code. It occurs sporadically in the testsuite, and
many times in 403.gcc: the final bitcode has 131 fewer subtractions after this change.
The reason that the multiplies are not eliminated is the same reason that instcombine
did not catch this: they are used by other instructions (instcombine catches this with
a more general transform which in general is only profitable if the operands have only
one use).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123754 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'test/Transforms/InstSimplify/2010-12-20-Distribute.ll')
-rw-r--r-- | test/Transforms/InstSimplify/2010-12-20-Distribute.ll | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/test/Transforms/InstSimplify/2010-12-20-Distribute.ll b/test/Transforms/InstSimplify/2010-12-20-Distribute.ll index 60cef48446..d20abd68c2 100644 --- a/test/Transforms/InstSimplify/2010-12-20-Distribute.ll +++ b/test/Transforms/InstSimplify/2010-12-20-Distribute.ll @@ -31,6 +31,26 @@ define i32 @factorize3(i32 %x, i32 %a, i32 %b) { ; CHECK: ret i32 %r } +define i32 @factorize4(i32 %x, i32 %y) { +; CHECK: @factorize4 + %sh = shl i32 %y, 1 + %ml = mul i32 %sh, %x + %mr = mul i32 %x, %y + %s = sub i32 %ml, %mr + ret i32 %s +; CHECK: ret i32 %mr +} + +define i32 @factorize5(i32 %x, i32 %y) { +; CHECK: @factorize5 + %sh = mul i32 %y, 2 + %ml = mul i32 %sh, %x + %mr = mul i32 %x, %y + %s = sub i32 %ml, %mr + ret i32 %s +; CHECK: ret i32 %mr +} + define i32 @expand(i32 %x) { ; CHECK: @expand ; ((X & 1) | 2) & 1 -> ((X & 1) & 1) | (2 & 1) -> (X & 1) | 0 -> X & 1 |