[PeepholeOpt] Don't stop simplifying copies on sequence of subregs
This patch removes an overly conservative check that would prevent
simplifying copies when the value we were tracking would go through
several subregister indices.
Indeed, the intend of this check was to not track values whenever
we have to compose subregister, but actually what the check was
doing was bailing anytime we see a second subreg, even if that
second subreg would actually be the new source of truth (as opposed
to a part of that subreg).
Differential Revision: https://reviews.llvm.org/D59891
llvm-svn: 357095
diff --git a/llvm/lib/CodeGen/PeepholeOptimizer.cpp b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
index f527749..2307e99 100644
--- a/llvm/lib/CodeGen/PeepholeOptimizer.cpp
+++ b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
@@ -1900,13 +1900,8 @@
// Def = REG_SEQUENCE v0, sub0, v1, sub1, ...
// Check if one of the operand defines the subreg we are interested in.
for (const RegSubRegPairAndIdx &RegSeqInput : RegSeqInputRegs) {
- if (RegSeqInput.SubIdx == DefSubReg) {
- if (RegSeqInput.SubReg)
- // Bail if we have to compose sub registers.
- return ValueTrackerResult();
-
+ if (RegSeqInput.SubIdx == DefSubReg)
return ValueTrackerResult(RegSeqInput.Reg, RegSeqInput.SubReg);
- }
}
// If the subreg we are tracking is super-defined by another subreg,