[llvm-dev] Potential bug in SelectionDAGLegalize::ConvertNodeToLibcall()?

Justin Hibbits via llvm-dev llvm-dev at lists.llvm.org
Wed Jan 2 07:53:53 PST 2019


I have a custom lowering operation on ISD::BITCAST for the PowerPC/SPE
target, to convert 'f64 bitcast (i64 build_pair i32, i32)' into a 'f64
BUILD_SPE64 i32, i32' node, which can be seen at
https://reviews.llvm.org/D54583. However, when building compiler-rt's
lib/builtins/divdc3.c an assertion is triggered that BUILD_PAIR is not
legal on line 24.  There should be no bitcast(buildpair) anywhere in
the generation, as it should all be lowered.  However, this is not the
case when lowering to a libcall it seems.  The relevant debug output,
is here:

Creating new node: t118: i64 = build_pair t117,t116, /home/chmeee/freebsd/contrib/compiler-rt/lib/builtins/divdc3.c:24:22
Creating new node: t119: f64 = bitcast t118, /home/chmeee/freebsd/contrib/compiler-rt/lib/builtins/divdc3.c:24:22
Created libcall: t119: f64 = bitcast t118, /home/chmeee/freebsd/contrib/compiler-rt/lib/builtins/divdc3.c:24:22
Successfully converted node to libcall
 ... replacing: t38: f64 = fmaxnum t36, t37, /home/chmeee/freebsd/contrib/compiler-rt/lib/builtins/divdc3.c:24:22
     with:      t119: f64 = bitcast t118, /home/chmeee/freebsd/contrib/compiler-rt/lib/builtins/divdc3.c:24:22

Is this a real bug, or am I missing something in my patch?  After
spending quite a while on it I'm at a loss.


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