[PPC] Better codegen for AND, ANY_EXT, SRL sequence
https://reviews.llvm.org/D24924
This improves the code generated for a sequence of AND, ANY_EXT, SRL instructions. This is a targetted fix for this special pattern. The pattern is generated by target independet dag combiner and so a more general fix may not be necessary. If we come across other similar cases, some ideas for handling it are discussed on the code review.
llvm-svn: 284983
diff --git a/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp b/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
index 150b0c8..1395a4b 100644
--- a/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelDAGToDAG.cpp
@@ -2657,6 +2657,23 @@
MB = 64 - countTrailingOnes(Imm64);
SH = 0;
+ if (Val.getOpcode() == ISD::ANY_EXTEND) {
+ auto Op0 = Val.getOperand(0);
+ if ( Op0.getOpcode() == ISD::SRL &&
+ isInt32Immediate(Op0.getOperand(1).getNode(), Imm) && Imm <= MB) {
+
+ auto ResultType = Val.getNode()->getValueType(0);
+ auto ImDef = CurDAG->getMachineNode(PPC::IMPLICIT_DEF, dl,
+ ResultType);
+ SDValue IDVal (ImDef, 0);
+
+ Val = SDValue(CurDAG->getMachineNode(PPC::INSERT_SUBREG, dl,
+ ResultType, IDVal, Op0.getOperand(0),
+ getI32Imm(1, dl)), 0);
+ SH = 64 - Imm;
+ }
+ }
+
// If the operand is a logical right shift, we can fold it into this
// instruction: rldicl(rldicl(x, 64-n, n), 0, mb) -> rldicl(x, 64-n, mb)
// for n <= mb. The right shift is really a left rotate followed by a
diff --git a/llvm/lib/Target/PowerPC/README.txt b/llvm/lib/Target/PowerPC/README.txt
index f1d4ca7..82c7239 100644
--- a/llvm/lib/Target/PowerPC/README.txt
+++ b/llvm/lib/Target/PowerPC/README.txt
@@ -658,3 +658,9 @@
ISA 2.07. LLVM needs to add infrastructure to recognize fusion opportunities
and force instruction pairs to be scheduled together.
+-----------------------------------------------------------------------------
+
+More general handling of any_extend and zero_extend:
+
+See https://reviews.llvm.org/D24924#555306
+
diff --git a/llvm/test/CodeGen/PowerPC/anyext_srl.ll b/llvm/test/CodeGen/PowerPC/anyext_srl.ll
new file mode 100644
index 0000000..1d729d2
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/anyext_srl.ll
@@ -0,0 +1,29 @@
+; RUN: llc -verify-machineinstrs -mtriple=powerpc64le-unknown-linux-gnu \
+; RUN: -mcpu=pwr8 < %s | FileCheck %s
+
+%class.PB2 = type { [1 x i32], %class.PB1* }
+%class.PB1 = type { [1 x i32], i64, i64, i32 }
+
+; Function Attrs: norecurse nounwind readonly
+define zeroext i1 @foo(%class.PB2* %s_a, %class.PB2* %s_b) local_unnamed_addr {
+entry:
+ %arrayidx.i6 = bitcast %class.PB2* %s_a to i32*
+ %0 = load i32, i32* %arrayidx.i6, align 8, !tbaa !1
+ %and.i = and i32 %0, 8
+ %cmp.i = icmp ne i32 %and.i, 0
+ %arrayidx.i37 = bitcast %class.PB2* %s_b to i32*
+ %1 = load i32, i32* %arrayidx.i37, align 8, !tbaa !1
+ %and.i4 = and i32 %1, 8
+ %cmp.i5 = icmp ne i32 %and.i4, 0
+ %cmp = xor i1 %cmp.i, %cmp.i5
+ ret i1 %cmp
+; CHECK-LABEL: @foo
+; CHECK: rldicl {{[0-9]+}}, {{[0-9]+}}, 61, 63
+
+}
+
+!1 = !{!2, !2, i64 0}
+!2 = !{!"int", !3, i64 0}
+!3 = !{!"omnipotent char", !4, i64 0}
+!4 = !{!"Simple C++ TBAA"}
+