Replace sra with srl if a single sign bit is required

E.g. (and (sra (i32 x) 31) 2) -> (and (srl (i32 x) 30) 2).

llvm-svn: 192884

2 files changed, 16 insertions, 5 deletions

diff --git a/llvm/test/CodeGen/PowerPC/rlwimi-and.ll b/llvm/test/CodeGen/PowerPC/rlwimi-and.ll
index e20a13fec0f..7963249ddf8 100644
--- a/llvm/test/CodeGen/PowerPC/rlwimi-and.ll
+++ b/llvm/test/CodeGen/PowerPC/rlwimi-and.ll
@@ -28,12 +28,11 @@ codeRepl17:                                       ; preds = %codeRepl4
   store i16 %rvml38.sroa.0.0.insert.insert, i16* undef, align 2
   unreachable
 
+; FIXME: the SLWI could be folded into the RLWIMI to give a rotate of 8.
 ; CHECK: @test
-; CHECK-DAG: slwi [[R1:[0-9]+]],
-; CHECK-DAG: rlwinm [[R2:[0-9]+]],
-; CHECK-DAG: srawi [[R3:[0-9]+]], [[R1]]
-; CHECK-DAG: rlwinm [[R4:[0-9]+]], [[R3]], 0, 23, 23
-; CHECK: rlwimi [[R4]], [[R2]], 0,
+; CHECK-DAG: slwi [[R1:[0-9]+]], {{[0-9]+}}, 31
+; CHECK-DAG: rlwinm [[R2:[0-9]+]], {{[0-9]+}}, 0, 31, 31
+; CHECK: rlwimi [[R2]], [[R1]], 9, 23, 23
 
 codeRepl29:                                       ; preds = %codeRepl1
   unreachable
diff --git a/llvm/test/CodeGen/SystemZ/shift-10.ll b/llvm/test/CodeGen/SystemZ/shift-10.ll
index 3fd965745ed..46ed2180dfd 100644
--- a/llvm/test/CodeGen/SystemZ/shift-10.ll
+++ b/llvm/test/CodeGen/SystemZ/shift-10.ll
@@ -64,3 +64,15 @@ define i64 @f5(i32 %a) {
   %or = or i64 %shl, 7
   ret i64 %or
 }
+
+; Test that SRA gets replaced with SRL if the sign bit is the only one
+; that matters.
+define i64 @f6(i64 %a) {
+; CHECK-LABEL: f6:
+; CHECK: risbg %r2, %r2, 55, 183, 19
+; CHECK: br %r14
+  %shl = shl i64 %a, 10
+  %shr = ashr i64 %shl, 60
+  %and = and i64 %shr, 256
+  ret i64 %and
+}