From 1fd4e558289771a2d5b70f0da8155e0ba2721a49 Mon Sep 17 00:00:00 2001
From: Richard Sandiford <rsandifo@linux.vnet.ibm.com>
Date: Fri, 20 Dec 2013 11:49:48 +0000
Subject: [PATCH] [SystemZ] Extend RISBG optimization

The handling of ANY_EXTEND and ZERO_EXTEND was too strict.  In this context
we can treat ZERO_EXTEND in much the same way as an AND and then also handle
outermost ZERO_EXTENDs.

I couldn't find a test that benefited from the ANY_EXTEND change, but it's
more obvious to write it this way once SIGN_EXTEND and ZERO_EXTEND are
handled differently.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@197802 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/SystemZ/SystemZISelDAGToDAG.cpp | 20 +++++++++++++++++---
 test/CodeGen/SystemZ/risbg-01.ll           | 15 +++++++++++++--
 2 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp b/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
index f4a27733ce0..567a6b7451f 100644
--- a/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
+++ b/lib/Target/SystemZ/SystemZISelDAGToDAG.cpp
@@ -764,9 +764,22 @@ bool SystemZDAGToDAGISel::expandRxSBG(RxSBGOperands &RxSBG) const {
     return true;
   }
       
-  case ISD::SIGN_EXTEND:
-  case ISD::ZERO_EXTEND:
-  case ISD::ANY_EXTEND: {
+  case ISD::ANY_EXTEND:
+    // Bits above the extended operand are don't-care.
+    RxSBG.Input = N.getOperand(0);
+    return true;
+
+  case ISD::ZERO_EXTEND: {
+    // Restrict the mask to the extended operand.
+    unsigned InnerBitSize = N.getOperand(0).getValueType().getSizeInBits();
+    if (!refineRxSBGMask(RxSBG, allOnes(InnerBitSize)))
+      return false;
+
+    RxSBG.Input = N.getOperand(0);
+    return true;
+  }
+    
+  case ISD::SIGN_EXTEND: {
     // Check that the extension bits are don't-care (i.e. are masked out
     // by the final mask).
     unsigned InnerBitSize = N.getOperand(0).getValueType().getSizeInBits();
@@ -1064,6 +1077,7 @@ SDNode *SystemZDAGToDAGISel::Select(SDNode *Node) {
   case ISD::ROTL:
   case ISD::SHL:
   case ISD::SRL:
+  case ISD::ZERO_EXTEND:
     if (!ResNode)
       ResNode = tryRISBGZero(Node);
     break;
diff --git a/test/CodeGen/SystemZ/risbg-01.ll b/test/CodeGen/SystemZ/risbg-01.ll
index a4d11fdae5b..e303067e539 100644
--- a/test/CodeGen/SystemZ/risbg-01.ll
+++ b/test/CodeGen/SystemZ/risbg-01.ll
@@ -457,11 +457,22 @@ define i64 @f40(i64 %foo, i64 *%dest) {
   ret i64 %and
 }
 
+; Check a case where the result is zero-extended.
+define i64 @f41(i32 %a) {
+; CHECK-LABEL: f41
+; CHECK: risbg %r2, %r2, 36, 191, 62
+; CHECK: br %r14
+  %shl = shl i32 %a, 2
+  %shr = lshr i32 %shl, 4
+  %ext = zext i32 %shr to i64
+  ret i64 %ext
+}
+
 ; In this case the sign extension is converted to a pair of 32-bit shifts,
 ; which is then extended to 64 bits.  We previously used the wrong bit size
 ; when testing whether the shifted-in bits of the shift right were significant.
-define i64 @f41(i1 %x) {
-; CHECK-LABEL: f41:
+define i64 @f42(i1 %x) {
+; CHECK-LABEL: f42:
 ; CHECK: sll %r2, 31
 ; CHECK: sra %r2, 31
 ; CHECK: llgcr %r2, %r2
-- 
2.34.1