[AVR] Implement stacksave/stackrestore by expanding (PR31342)

Summary:
Authored by Florian Zeitz.

This implements the missing stacksave/stackrestore intrinsics via expansion.

Output of `llc -O0 -march=avr ~/devel/llvm/test/CodeGen/Generic/stacksave-restore.ll` for sanity checking (comments mine):

```
	.text
	.file	".../llvm/test/CodeGen/Generic/stacksave-restore.ll"
	.globl	test
	.p2align	1
	.type	test,@function
test:                                   ; @test
; BB#0:
	push	r28
	push	r29

	in	r28, 61
	in	r29, 62
	sbiw	r28, 4
	in	r0, 63
	cli
	out	62, r29
	out	63, r0
	out	61, r28

	in	r18, 61
	in	r19, 62

	mov	r20, r22
	mov	r21, r23

	in	r30, 61
	in	r31, 62

	lsl	r22
	rol	r23
	lsl	r22
	rol	r23
	in	r26, 61
	in	r27, 62
	sub	r26, r22
	sbc	r27, r23
	andi	r26, 252
	in	r0, 63
	cli
	out	62, r27
	out	63, r0
	out	61, r26

	in	r0, 63
	cli
	out	62, r31
	out	63, r0
	out	61, r30

	in	r30, 61
	in	r31, 62
	sub	r30, r22
	sbc	r31, r23
	andi	r30, 252
	in	r0, 63
	cli
	out	62, r31
	out	63, r0
	out	61, r30

	std	Y+3, r24                ; 2-byte Folded Spill
	std	Y+4, r25                ; 2-byte Folded Spill

	mov	r24, r26
	mov	r25, r27

	in	r0, 63
	cli
	out	62, r19
	out	63, r0
	out	61, r18

	std	Y+1, r20                ; 2-byte Folded Spill
	std	Y+2, r21                ; 2-byte Folded Spill

	adiw	r28, 4
	in	r0, 63
	cli
	out	62, r29
	out	63, r0
	out	61, r28

	pop	r29
	pop	r28
	ret
.Lfunc_end0:
	.size	test, .Lfunc_end0-test
```

Reviewers: dylanmckay

Reviewed By: dylanmckay

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D29553

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294146 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/AVR/AVRISelLowering.cpp b/lib/Target/AVR/AVRISelLowering.cpp
index fa2a391820636141c58edcf11e3328ce475b3d96..0f0d1de89a6533700b4425c60a4cab3c1c1e90fb 100644 (file)
--- a/lib/Target/AVR/AVRISelLowering.cpp
+++ b/lib/Target/AVR/AVRISelLowering.cpp
@@ -48,6 +48,8 @@ AVRTargetLowering::AVRTargetLowering(AVRTargetMachine &tm)
   setOperationAction(ISD::GlobalAddress, MVT::i16, Custom);
   setOperationAction(ISD::BlockAddress, MVT::i16, Custom);
 
+  setOperationAction(ISD::STACKSAVE, MVT::Other, Expand);
+  setOperationAction(ISD::STACKRESTORE, MVT::Other, Expand);
   setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i8, Expand);
   setOperationAction(ISD::DYNAMIC_STACKALLOC, MVT::i16, Expand);
 

diff --git a/test/CodeGen/AVR/intrinsics/stacksave-restore.ll b/test/CodeGen/AVR/intrinsics/stacksave-restore.ll
new file mode 100644 (file)
index 0000000..3985f49
--- /dev/null
+++ b/test/CodeGen/AVR/intrinsics/stacksave-restore.ll
@@ -0,0 +1,27 @@
+; RUN: llc -O0 < %s -march=avr | FileCheck %s
+
+; CHECK-LABEL: foo
+define void @foo() {
+entry:
+  br label %save
+
+; CHECK-LABEL: save
+; CHECK: in [[SREG1:r[0-9]+]], 61
+; CHECK-NEXT: in [[SREG2:r[0-9]+]], 62
+save:
+  %saved = call i8* @llvm.stacksave()
+  br label %restore
+
+; CHECK-LABEL: restore
+; CHECK: in r0, 63
+; CHECK-NEXT: cli
+; CHECK-NEXT: out 62, [[SREG2]]
+; CHECK-NEXT: out 63, r0
+; CHECK-NEXT: out 61, [[SREG1]]
+restore:
+  call void @llvm.stackrestore(i8* %saved)
+  ret void
+}
+
+declare i8* @llvm.stacksave()
+declare void @llvm.stackrestore(i8* %ptr)