SimplifyDemandedBits. The idea is that some operations can be simplified if
not all of the computed elements are needed. Some targets (like x86) have a
large number of intrinsics that operate on a single element, but pass other
elts through unmodified. If those other elements are not needed, the
intrinsics can be simplified to scalar operations, and insertelement ops can
be removed.
This turns (f.e.):
ushort %Convert_sse(float %f) {
%tmp = insertelement <4 x float> undef, float %f, uint 0 ; <<4 x float>> [#uses=1]
%tmp10 = insertelement <4 x float> %tmp, float 0.000000e+00, uint 1 ; <<4 x float>> [#uses=1]
%tmp11 = insertelement <4 x float> %tmp10, float 0.000000e+00, uint 2 ; <<4 x float>> [#uses=1]
%tmp12 = insertelement <4 x float> %tmp11, float 0.000000e+00, uint 3 ; <<4 x float>> [#uses=1]
%tmp28 = tail call <4 x float> %llvm.x86.sse.sub.ss( <4 x float> %tmp12, <4 x float> < float 1.000000e+00, float 0.000000e+00, float 0.000000e+00, float 0.000000e+00 > ) ; <<4 x float>> [#uses=1]
%tmp37 = tail call <4 x float> %llvm.x86.sse.mul.ss( <4 x float> %tmp28, <4 x float> < float 5.000000e-01, float 0.000000e+00, float 0.000000e+00, float 0.000000e+00 > ) ; <<4 x float>> [#uses=1]
%tmp48 = tail call <4 x float> %llvm.x86.sse.min.ss( <4 x float> %tmp37, <4 x float> < float 6.553500e+04, float 0.000000e+00, float 0.000000e+00, float 0.000000e+00 > ) ; <<4 x float>> [#uses=1]
%tmp59 = tail call <4 x float> %llvm.x86.sse.max.ss( <4 x float> %tmp48, <4 x float> zeroinitializer ) ; <<4 x float>> [#uses=1]
%tmp = tail call int %llvm.x86.sse.cvttss2si( <4 x float> %tmp59 ) ; <int> [#uses=1]
%tmp69 = cast int %tmp to ushort ; <ushort> [#uses=1]
ret ushort %tmp69
}
into:
ushort %Convert_sse(float %f) {
entry:
%tmp28 = sub float %f, 1.000000e+00 ; <float> [#uses=1]
%tmp37 = mul float %tmp28, 5.000000e-01 ; <float> [#uses=1]
%tmp375 = insertelement <4 x float> undef, float %tmp37, uint 0 ; <<4 x float>> [#uses=1]
%tmp48 = tail call <4 x float> %llvm.x86.sse.min.ss( <4 x float> %tmp375, <4 x float> < float 6.553500e+04, float undef, float undef, float undef > ) ; <<4 x float>> [#uses=1]
%tmp59 = tail call <4 x float> %llvm.x86.sse.max.ss( <4 x float> %tmp48, <4 x float> < float 0.000000e+00, float undef, float undef, float undef > ) ; <<4 x float>> [#uses=1]
%tmp = tail call int %llvm.x86.sse.cvttss2si( <4 x float> %tmp59 ) ; <int> [#uses=1]
%tmp69 = cast int %tmp to ushort ; <ushort> [#uses=1]
ret ushort %tmp69
}
which improves codegen from:
_Convert_sse:
movss LCPI1_0, %xmm0
movss 4(%esp), %xmm1
subss %xmm0, %xmm1
movss LCPI1_1, %xmm0
mulss %xmm0, %xmm1
movss LCPI1_2, %xmm0
minss %xmm0, %xmm1
xorps %xmm0, %xmm0
maxss %xmm0, %xmm1
cvttss2si %xmm1, %eax
andl $65535, %eax
ret
to:
_Convert_sse:
movss 4(%esp), %xmm0
subss LCPI1_0, %xmm0
mulss LCPI1_1, %xmm0
movss LCPI1_2, %xmm1
minss %xmm1, %xmm0
xorps %xmm1, %xmm1
maxss %xmm1, %xmm0
cvttss2si %xmm0, %eax
andl $65535, %eax
ret
This is just a first step, it can be extended in many ways. Testcase here:
Transforms/InstCombine/vec_demanded_elts.ll
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30752 91177308-0d34-0410-b5e6-96231b3b80d8
Ensure that we copy KnownProperties before calling visitBasicBlock, else
we may leak properties into blocks where they don't belong.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30705 91177308-0d34-0410-b5e6-96231b3b80d8
that we can't modify the CFG any more, at least not until it's possible
to update the dominator tree (PR217).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30469 91177308-0d34-0410-b5e6-96231b3b80d8
operations (like findProperties) should be faster, at the expense of
unionSets being slower in cases that are rare in practise.
Don't erase a dead Instruction. This fixes a memory corruption issue.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30235 91177308-0d34-0410-b5e6-96231b3b80d8
Reorder operations to remove duplicated work.
Fix to leave floating-point types out of the optimization.
Add tests to predsimplify.ll for SwitchInst and SelectInst handling.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30055 91177308-0d34-0410-b5e6-96231b3b80d8
another Value) weren't being found by findProperties.
This fixes predsimplify.ll test6, a missed optimization opportunity.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29991 91177308-0d34-0410-b5e6-96231b3b80d8
If a branch's condition has become a ConstantBool, simplify it immediately.
Removing the edge saves work and exposes up more optimization opportunities
in the pass.
Add support for SelectInst.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29970 91177308-0d34-0410-b5e6-96231b3b80d8
exit blocks. The output is dependent on addresses of basic block.
Add and use Loop::getUniqueExitBlocks.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29966 91177308-0d34-0410-b5e6-96231b3b80d8
