[Hexagon] Use constant extenders to fix up hardware loops

Use a loop instruction with a constant extender for a hardware
loop instruction that is too far away from the start of the loop.
This is cheaper than changing the SA register value.

Differential Revision: http://reviews.llvm.org/D9262

llvm-svn: 235882

1 files changed, 36 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/Hexagon/hwloop-range.ll b/llvm/test/CodeGen/Hexagon/hwloop-range.ll
new file mode 100644
index 00000000000..5e6fe78d0e0
--- /dev/null
+++ b/llvm/test/CodeGen/Hexagon/hwloop-range.ll
@@ -0,0 +1,36 @@
+; RUN: llc -march=hexagon -hexagon-loop-range=0 < %s | FileCheck %s
+
+; Test that the loop start address operand uses a constant extender
+; if the offset is out of range.
+
+; CHECK: loop0(##.LBB
+; CHECK: endloop0
+
+@g = external global i32, align 4
+
+define void @test(i32* nocapture %a, i32* nocapture readonly %b, i32 %n) #0 {
+entry:
+  %cmp6 = icmp slt i32 %n, 1
+  br i1 %cmp6, label %for.end, label %for.body.preheader
+
+for.body.preheader:
+  br label %for.body
+
+for.body:
+  %i.07 = phi i32 [ %inc, %for.body ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i32, i32* %b, i32 %i.07
+  %0 = load i32, i32* %arrayidx, align 4
+  %1 = load i32, i32* @g, align 4
+  %mul = mul nsw i32 %1, %0
+  %arrayidx1 = getelementptr inbounds i32, i32* %a, i32 %i.07
+  store i32 %mul, i32* %arrayidx1, align 4
+  %inc = add nuw nsw i32 %i.07, 1
+  %exitcond = icmp eq i32 %inc, %n
+  br i1 %exitcond, label %for.end.loopexit, label %for.body
+
+for.end.loopexit:
+  br label %for.end
+
+for.end:
+  ret void
+}