Increase opportunities to optimize (brcond (srl (and c1), c2)).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91717 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 6cef239..e6aa14c 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2755,7 +2755,34 @@
if (N1C && SimplifyDemandedBits(SDValue(N, 0)))
return SDValue(N, 0);
- return N1C ? visitShiftByConstant(N, N1C->getZExtValue()) : SDValue();
+ if (N1C) {
+ SDValue NewSRL = visitShiftByConstant(N, N1C->getZExtValue());
+ if (NewSRL.getNode())
+ return NewSRL;
+ }
+
+ // Here is a common situation. We want to optimize:
+ //
+ // %a = ...
+ // %b = and i32 %a, 2
+ // %c = srl i32 %b, 1
+ // brcond i32 %c ...
+ //
+ // into
+ //
+ // %a = ...
+ // %b = and %a, 2
+ // %c = setcc eq %b, 0
+ // brcond %c ...
+ //
+ // However when after the source operand of SRL is optimized into AND, the SRL
+ // itself may not be optimized further. Look for it and add the BRCOND into
+ // the worklist.
+ if (N->hasOneUse() &&
+ N->use_begin()->getOpcode() == ISD::BRCOND)
+ AddToWorkList(*N->use_begin());
+
+ return SDValue();
}
SDValue DAGCombiner::visitCTLZ(SDNode *N) {
diff --git a/test/CodeGen/X86/brcond-srl.ll b/test/CodeGen/X86/brcond-srl.ll
new file mode 100644
index 0000000..12674e9
--- /dev/null
+++ b/test/CodeGen/X86/brcond-srl.ll
@@ -0,0 +1,29 @@
+; RUN: llc < %s -march=x86 | FileCheck %s
+; rdar://7475489
+
+define i32 @t(i32 %a, i32 %b) nounwind ssp {
+entry:
+; CHECK: t:
+; CHECK: xorb
+; CHECK-NOT: andb
+; CHECK-NOT: shrb
+; CHECK: testb $64
+ %0 = and i32 %a, 16384
+ %1 = icmp ne i32 %0, 0
+ %2 = and i32 %b, 16384
+ %3 = icmp ne i32 %2, 0
+ %4 = xor i1 %1, %3
+ br i1 %4, label %bb1, label %bb
+
+bb: ; preds = %entry
+ %5 = tail call i32 (...)* @foo() nounwind ; <i32> [#uses=1]
+ ret i32 %5
+
+bb1: ; preds = %entry
+ %6 = tail call i32 (...)* @bar() nounwind ; <i32> [#uses=1]
+ ret i32 %6
+}
+
+declare i32 @foo(...)
+
+declare i32 @bar(...)