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Summary:
SPE passes doubles the same as soft-float, in register pairs as i32
types. This is all handled by the target-independent layer. However,
this is not optimal when splitting or reforming the doubles, as it
pushes to the stack and loads from, on either side.
For instance, to pass a double argument to a function, assuming the
double value is in r5, the sequence currently looks like this:
evstdd 5, X(1)
lwz 3, X(1)
lwz 4, X+4(1)
Likewise, to form a double into r5 from args in r3 and r4:
stw 3, X(1)
stw 4, X+4(1)
evldd 5, X(1)
This optimizes the fence to use SPE instructions. Now, to pass a double
to a function:
mr 4, 5
evmergehi 3, 5, 5
And to form a double into r5 from args in r3 and r4:
evmergelo 5, 3, 4
This is comparable to the way that gcc generates the double splits.
This also fixes a bug with expanding builtins to libcalls, where the
LowerCallTo() code path was generating intermediate illegal type nodes.
Reviewers: nemanjai, hfinkel, joerg
Subscribers: kbarton, jfb, jsji, llvm-commits
Differential Revision: https://reviews.llvm.org/D54583
llvm-svn: 363526
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