[PowerPC] Fix handling of undefs in the PPC::isSplatShuffleMask query #145149
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@llvm/pr-subscribers-backend-powerpc Author: Wael Yehia (w2yehia) ChangesCurrently, the query assumes that a single undef bit implies the rest of the Full diff: https://github.com/llvm/llvm-project/pull/145149.diff 2 Files Affected:
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index f502d8570425a..d1b17f227a684 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -2242,8 +2242,13 @@ bool PPC::isSplatShuffleMask(ShuffleVectorSDNode *N, unsigned EltSize) {
return false;
for (unsigned i = EltSize, e = 16; i != e; i += EltSize) {
- if (N->getMaskElt(i) < 0) continue;
- for (unsigned j = 0; j != EltSize; ++j)
+ // An UNDEF element is a sequence of UNDEF bits.
+ if (N->getMaskElt(i) < 0) {
+ for (unsigned j = 1; j != EltSize; ++j)
+ if (N->getMaskElt(i+j) >= 0)
+ return false;
+ }
+ else for (unsigned j = 0; j != EltSize; ++j)
if (N->getMaskElt(i+j) != N->getMaskElt(j))
return false;
}
diff --git a/llvm/test/CodeGen/PowerPC/pr141642.ll b/llvm/test/CodeGen/PowerPC/pr141642.ll
new file mode 100644
index 0000000000000..38a7065747867
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/pr141642.ll
@@ -0,0 +1,13 @@
+; RUN: llc -mcpu=pwr8 -mtriple=powerpc64le-unknown-linux-gnu -O0 -debug-only=selectiondag -o - < %s 2>&1 | \
+; RUN: FileCheck %s
+; CHECK-NOT: lxvdsx
+; CHECK-NOT: LD_SPLAT
+
+define weak_odr dso_local void @unpack(ptr noalias noundef %packed_in) local_unnamed_addr {
+entry:
+ %ld = load <2 x i32>, ptr %packed_in, align 2
+ %shuf = shufflevector <2 x i32> %ld, <2 x i32> poison, <4 x i32> <i32 0, i32 1, i32 poison, i32 0>
+ %ie = insertelement <4 x i32> %shuf, i32 7, i32 2
+ store <4 x i32> %shuf, ptr %packed_in, align 2
+ ret void
+}
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You can test this locally with the following command:git-clang-format --diff HEAD~1 HEAD --extensions cpp -- llvm/lib/Target/PowerPC/PPCISelLowering.cppView the diff from clang-format here.diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index d1b17f227..967ebc4cb 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -2245,12 +2245,12 @@ bool PPC::isSplatShuffleMask(ShuffleVectorSDNode *N, unsigned EltSize) {
// An UNDEF element is a sequence of UNDEF bits.
if (N->getMaskElt(i) < 0) {
for (unsigned j = 1; j != EltSize; ++j)
- if (N->getMaskElt(i+j) >= 0)
+ if (N->getMaskElt(i + j) >= 0)
+ return false;
+ } else
+ for (unsigned j = 0; j != EltSize; ++j)
+ if (N->getMaskElt(i + j) != N->getMaskElt(j))
return false;
- }
- else for (unsigned j = 0; j != EltSize; ++j)
- if (N->getMaskElt(i+j) != N->getMaskElt(j))
- return false;
}
return true;
}
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Currently, the query assumes that a single undef bit implies the rest of the
EltSize - 1bits are undefs, but that's not always true.e.g. isSplatShuffleMask( <0,1,2,3,4,5,6,7,undef,undef,undef,undef,0,1,2,3>, 8) should return false.