Experimental support for aligned NEON spills.

ARM targets with NEON units have access to aligned vector loads and
stores that are potentially faster than unaligned operations.

Add support for spilling the callee-saved NEON registers to an aligned
stack area using 16-byte aligned NEON loads and store.

This feature is off by default, controlled by an -align-neon-spills
command line option.

llvm-svn: 147211

1 files changed, 73 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/Thumb2/aligned-spill.ll b/llvm/test/CodeGen/Thumb2/aligned-spill.ll
index 1a987d02d07..948c8ce2c2d 100644
--- a/llvm/test/CodeGen/Thumb2/aligned-spill.ll
+++ b/llvm/test/CodeGen/Thumb2/aligned-spill.ll
@@ -1,4 +1,5 @@
 ; RUN: llc < %s -mcpu=cortex-a8 | FileCheck %s
+; RUN: llc < %s -mcpu=cortex-a8 -align-neon-spills | FileCheck %s --check-prefix=NEON
 target datalayout = "e-p:32:32:32-i1:8:32-i8:8:32-i16:16:32-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:32:64-v128:32:128-a0:0:32-n32-S32"
 target triple = "thumbv7-apple-ios"
 
@@ -19,4 +20,76 @@ entry:
   ret void
 }
 
+; NEON: f
+; NEON: push {r4, r7, lr}
+; NEON: sub.w r4, sp, #64
+; NEON: bic r4, r4, #15
+; Stack pointer must be updated before the spills.
+; NEON: mov sp, r4
+; NEON: vst1.64 {d8, d9, d10, d11}, [r4, :128]!
+; NEON: vst1.64 {d12, d13, d14, d15}, [r4, :128]
+; Stack pointer adjustment for the stack frame contents.
+; This could legally happen before the spills.
+; Since the spill slot is only 8 bytes, technically it would be fine to only
+; subtract #8 here. That would leave sp less aligned than some stack slots,
+; and would probably blow MFI's mind.
+; NEON: sub sp, #16
+; The epilog is free to use another scratch register than r4.
+; NEON: add r[[R4:[0-9]+]], sp, #16
+; NEON: vld1.64 {d8, d9, d10, d11}, [r[[R4]], :128]!
+; NEON: vld1.64 {d12, d13, d14, d15}, [r[[R4]], :128]
+; The stack pointer restore must happen after the reloads.
+; NEON: mov sp,
+; NEON: pop
+
 declare void @g()
+
+; Spill 7 d-registers.
+define void @f7(double* nocapture %p) nounwind ssp {
+entry:
+  tail call void asm sideeffect "", "~{d8},~{d9},~{d10},~{d11},~{d12},~{d13},~{d14}"() nounwind
+  ret void
+}
+
+; NEON: f7
+; NEON: push {r4, r7, lr}
+; NEON: sub.w r4, sp, #56
+; NEON: bic r4, r4, #15
+; Stack pointer must be updated before the spills.
+; NEON: mov sp, r4
+; NEON: vst1.64 {d8, d9, d10, d11}, [r4, :128]!
+; NEON: vst1.64 {d12, d13}, [r4, :128]
+; NEON: vstr d14, [r4, #16]
+; Epilog
+; NEON: vld1.64 {d8, d9, d10, d11},
+; NEON: vld1.64 {d12, d13},
+; NEON: vldr d14,
+; The stack pointer restore must happen after the reloads.
+; NEON: mov sp,
+; NEON: pop
+
+; Spill 7 d-registers, leave a hole.
+define void @f3plus4(double* nocapture %p) nounwind ssp {
+entry:
+  tail call void asm sideeffect "", "~{d8},~{d9},~{d10},~{d12},~{d13},~{d14},~{d15}"() nounwind
+  ret void
+}
+
+; Aligned spilling only works for contiguous ranges starting from d8.
+; The rest goes to the standard vpush instructions.
+; NEON: f3plus4
+; NEON: push {r4, r7, lr}
+; NEON: vpush {d12, d13, d14, d15}
+; NEON: sub.w r4, sp, #24
+; NEON: bic r4, r4, #15
+; Stack pointer must be updated before the spills.
+; NEON: mov sp, r4
+; NEON: vst1.64 {d8, d9}, [r4, :128]
+; NEON: vstr d10, [r4, #16]
+; Epilog
+; NEON: vld1.64 {d8, d9},
+; NEON: vldr d10, [{{.*}}, #16]
+; The stack pointer restore must happen after the reloads.
+; NEON: mov sp,
+; NEON: vpop {d12, d13, d14, d15}
+; NEON: pop