[mips] Add support for dynamic stack realignment.

Summary:
With this change we are able to realign the stack dynamically, whenever it
contains objects with alignment requirements that are larger than the
alignment specified from the given ABI.

We have to use the $fp register as the frame pointer when we perform
dynamic stack realignment. In complex stack frames, with variably-sized
objects, we reserve additionally the callee-saved register $s7 as the
base pointer in order to reference locals.

Reviewers: dsanders

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8633

llvm-svn: 238829

2 files changed, 301 insertions, 2 deletions

diff --git a/llvm/test/CodeGen/Mips/dynamic-stack-realignment.ll b/llvm/test/CodeGen/Mips/dynamic-stack-realignment.ll
new file mode 100644
index 00000000000..777930a37ad
--- /dev/null
+++ b/llvm/test/CodeGen/Mips/dynamic-stack-realignment.ll
@@ -0,0 +1,299 @@
+; RUN: llc < %s -march=mips -mcpu=mips2 | FileCheck %s \
+; RUN:    --check-prefix=ALL --check-prefix=GP32
+; RUN: llc < %s -march=mips -mcpu=mips32 | FileCheck %s \
+; RUN:    --check-prefix=ALL --check-prefix=GP32
+; RUN: llc < %s -march=mips -mcpu=mips32r6 | FileCheck %s \
+; RUN:    --check-prefix=ALL --check-prefix=GP32
+; RUN: llc < %s -march=mips64 -mcpu=mips3 | FileCheck %s \
+; RUN:    --check-prefix=ALL --check-prefix=GP64 -check-prefix=N64
+; RUN: llc < %s -march=mips64 -mcpu=mips64 | FileCheck %s \
+; RUN:    --check-prefix=ALL --check-prefix=GP64 -check-prefix=N64
+; RUN: llc < %s -march=mips64 -mcpu=mips64r6 | FileCheck %s \
+; RUN:    --check-prefix=ALL --check-prefix=GP64 -check-prefix=N64
+; RUN: llc < %s -march=mips64 -mcpu=mips3 -target-abi n32 | FileCheck %s \
+; RUN:    --check-prefix=ALL --check-prefix=GP64 -check-prefix=N32
+; RUN: llc < %s -march=mips64 -mcpu=mips64 -target-abi n32 | FileCheck %s \
+; RUN:    --check-prefix=ALL --check-prefix=GP64 -check-prefix=N32
+; RUN: llc < %s -march=mips64 -mcpu=mips64r6 -target-abi n32 | FileCheck %s \
+; RUN:    --check-prefix=ALL --check-prefix=GP64 -check-prefix=N32
+
+; Check dynamic stack realignment in functions without variable-sized objects.
+
+declare void @helper_01(i32, i32, i32, i32, i32*)
+
+; O32 ABI
+define void @func_01() {
+entry:
+; GP32-LABEL: func_01:
+
+  ; prologue
+  ; FIXME: We are currently over-allocating stack space. This particular case
+  ;        needs a frame of up to between 16 and 512-bytes but currently
+  ;        allocates between 1024 and 1536 bytes
+  ; GP32:       addiu   $sp, $sp, -1024
+  ; GP32:       sw      $ra, 1020($sp)
+  ; GP32:       sw      $fp, 1016($sp)
+  ;
+  ; GP32:       move    $fp, $sp
+  ; GP32:       addiu   $[[T0:[0-9]+|ra|gp]], $zero, -512
+  ; GP32-NEXT:  and     $sp, $sp, $[[T0]]
+
+  ; body
+  ; GP32:       addiu   $[[T1:[0-9]+]], $sp, 512
+  ; GP32:       sw      $[[T1]], 16($sp)
+
+  ; epilogue
+  ; GP32:       move    $sp, $fp
+  ; GP32:       lw      $fp, 1016($sp)
+  ; GP32:       lw      $ra, 1020($sp)
+  ; GP32:       addiu   $sp, $sp, 1024
+
+  %a = alloca i32, align 512
+  call void @helper_01(i32 0, i32 0, i32 0, i32 0, i32* %a)
+  ret void
+}
+
+declare void @helper_02(i32, i32, i32, i32,
+                        i32, i32, i32, i32, i32*)
+
+; N32/N64 ABIs
+define void @func_02() {
+entry:
+; GP64-LABEL: func_02:
+
+  ; prologue
+  ; FIXME: We are currently over-allocating stack space. This particular case
+  ;        needs a frame of up to between 16 and 512-bytes but currently
+  ;        allocates between 1024 and 1536 bytes
+  ; N32:        addiu   $sp, $sp, -1024
+  ; N64:        daddiu  $sp, $sp, -1024
+  ; GP64:       sd      $ra, 1016($sp)
+  ; GP64:       sd      $fp, 1008($sp)
+  ; N32:        sd      $gp, 1000($sp)
+  ;
+  ; GP64:       move    $fp, $sp
+  ; N32:        addiu   $[[T0:[0-9]+|ra]], $zero, -512
+  ; N64:        daddiu  $[[T0:[0-9]+|ra]], $zero, -512
+  ; GP64-NEXT:  and     $sp, $sp, $[[T0]]
+
+  ; body
+  ; N32:        addiu   $[[T1:[0-9]+]], $sp, 512
+  ; N64:        daddiu  $[[T1:[0-9]+]], $sp, 512
+  ; GP64:       sd      $[[T1]], 0($sp)
+
+  ; epilogue
+  ; GP64:       move    $sp, $fp
+  ; N32:        ld      $gp, 1000($sp)
+  ; GP64:       ld      $fp, 1008($sp)
+  ; GP64:       ld      $ra, 1016($sp)
+  ; N32:        addiu   $sp, $sp, 1024
+  ; N64:        daddiu  $sp, $sp, 1024
+
+  %a = alloca i32, align 512
+  call void @helper_02(i32 0, i32 0, i32 0, i32 0,
+                       i32 0, i32 0, i32 0, i32 0, i32* %a)
+  ret void
+}
+
+; Verify that we use $fp for referencing incoming arguments.
+
+declare void @helper_03(i32, i32, i32, i32, i32*, i32*)
+
+; O32 ABI
+define void @func_03(i32 %p0, i32 %p1, i32 %p2, i32 %p3, i32* %b) {
+entry:
+; GP32-LABEL: func_03:
+
+  ; body
+  ; FIXME: We are currently over-allocating stack space.
+  ; GP32-DAG:   addiu   $[[T0:[0-9]+]], $sp, 512
+  ; GP32-DAG:   sw      $[[T0]], 16($sp)
+  ; GP32-DAG:   lw      $[[T1:[0-9]+]], 1040($fp)
+  ; GP32-DAG:   sw      $[[T1]], 20($sp)
+
+  %a = alloca i32, align 512
+  call void @helper_03(i32 0, i32 0, i32 0, i32 0, i32* %a, i32* %b)
+  ret void
+}
+
+declare void @helper_04(i32, i32, i32, i32,
+                        i32, i32, i32, i32, i32*, i32*)
+
+; N32/N64 ABIs
+define void @func_04(i32 %p0, i32 %p1, i32 %p2, i32 %p3,
+                     i32 %p4, i32 %p5, i32 %p6, i32 %p7,
+                     i32* %b) {
+entry:
+; GP64-LABEL: func_04:
+
+  ; body
+  ; FIXME: We are currently over-allocating stack space.
+  ; N32-DAG:    addiu   $[[T0:[0-9]+]], $sp, 512
+  ; N64-DAG:    daddiu  $[[T0:[0-9]+]], $sp, 512
+  ; GP64-DAG:   sd      $[[T0]], 0($sp)
+  ; GP64-DAG:   ld      $[[T1:[0-9]+]], 1024($fp)
+  ; GP64-DAG:   sd      $[[T1]], 8($sp)
+
+  %a = alloca i32, align 512
+  call void @helper_04(i32 0, i32 0, i32 0, i32 0,
+                       i32 0, i32 0, i32 0, i32 0, i32* %a, i32* %b)
+  ret void
+}
+
+; Check dynamic stack realignment in functions with variable-sized objects.
+
+; O32 ABI
+define void @func_05(i32 %sz) {
+entry:
+; GP32-LABEL: func_05:
+
+  ; prologue
+  ; FIXME: We are currently over-allocating stack space.
+  ; GP32:       addiu   $sp, $sp, -1024
+  ; GP32:       sw      $fp, 1020($sp)
+  ; GP32:       sw      $23, 1016($sp)
+  ;
+  ; GP32:       move    $fp, $sp
+  ; GP32:       addiu   $[[T0:[0-9]+|gp]], $zero, -512
+  ; GP32-NEXT:  and     $sp, $sp, $[[T0]]
+  ; GP32-NEXT:  move    $23, $sp
+
+  ; body
+  ; GP32:       addiu   $[[T1:[0-9]+]], $zero, 222
+  ; GP32:       sw      $[[T1]], 508($23)
+
+  ; epilogue
+  ; GP32:       move    $sp, $fp
+  ; GP32:       lw      $23, 1016($sp)
+  ; GP32:       lw      $fp, 1020($sp)
+  ; GP32:       addiu   $sp, $sp, 1024
+
+  %a0 = alloca i32, i32 %sz, align 512
+  %a1 = alloca i32, align 4
+
+  store volatile i32 111, i32* %a0, align 512
+  store volatile i32 222, i32* %a1, align 4
+
+  ret void
+}
+
+; N32/N64 ABIs
+define void @func_06(i32 %sz) {
+entry:
+; GP64-LABEL: func_06:
+
+  ; prologue
+  ; FIXME: We are currently over-allocating stack space.
+  ; N32:        addiu   $sp, $sp, -1024
+  ; N64:        daddiu  $sp, $sp, -1024
+  ; GP64:       sd      $fp, 1016($sp)
+  ; GP64:       sd      $23, 1008($sp)
+  ;
+  ; GP64:       move    $fp, $sp
+  ; GP64:       addiu   $[[T0:[0-9]+|gp]], $zero, -512
+  ; GP64-NEXT:  and     $sp, $sp, $[[T0]]
+  ; GP64-NEXT:  move    $23, $sp
+
+  ; body
+  ; GP64:       addiu   $[[T1:[0-9]+]], $zero, 222
+  ; GP64:       sw      $[[T1]], 508($23)
+
+  ; epilogue
+  ; GP64:       move    $sp, $fp
+  ; GP64:       ld      $23, 1008($sp)
+  ; GP64:       ld      $fp, 1016($sp)
+  ; N32:        addiu   $sp, $sp, 1024
+  ; N64:        daddiu  $sp, $sp, 1024
+
+  %a0 = alloca i32, i32 %sz, align 512
+  %a1 = alloca i32, align 4
+
+  store volatile i32 111, i32* %a0, align 512
+  store volatile i32 222, i32* %a1, align 4
+
+  ret void
+}
+
+; Verify that we use $fp for referencing incoming arguments and $sp for
+; building outbound arguments for nested function calls.
+
+; O32 ABI
+define void @func_07(i32 %p0, i32 %p1, i32 %p2, i32 %p3, i32 %sz) {
+entry:
+; GP32-LABEL: func_07:
+
+  ; body
+  ; FIXME: We are currently over-allocating stack space.
+  ; GP32-DAG:       lw      $[[T0:[0-9]+]], 1040($fp)
+  ;
+  ; GP32-DAG:       addiu   $[[T1:[0-9]+]], $zero, 222
+  ; GP32-DAG:       sw      $[[T1]], 508($23)
+  ;
+  ; GP32-DAG:       sw      $[[T2:[0-9]+]], 16($sp)
+
+  %a0 = alloca i32, i32 %sz, align 512
+  %a1 = alloca i32, align 4
+
+  store volatile i32 111, i32* %a0, align 512
+  store volatile i32 222, i32* %a1, align 4
+
+  call void @helper_01(i32 0, i32 0, i32 0, i32 0, i32* %a1)
+
+  ret void
+}
+
+; N32/N64 ABIs
+define void @func_08(i32 %p0, i32 %p1, i32 %p2, i32 %p3,
+                     i32 %p4, i32 %p5, i32 %p6, i32 %p7,
+                     i32 %sz) {
+entry:
+; GP64-LABEL: func_08:
+
+  ; body
+  ; FIXME: We are currently over-allocating stack space.
+  ; N32-DAG:        lw      $[[T0:[0-9]+]], 1028($fp)
+  ; N64-DAG:        lwu     $[[T0:[0-9]+]], 1028($fp)
+  ;
+  ; GP64-DAG:       addiu   $[[T1:[0-9]+]], $zero, 222
+  ; GP64-DAG:       sw      $[[T1]], 508($23)
+  ;
+  ; GP64-DAG:       sd      $[[T2:[0-9]+]], 0($sp)
+
+  %a0 = alloca i32, i32 %sz, align 512
+  %a1 = alloca i32, align 4
+
+  store volatile i32 111, i32* %a0, align 512
+  store volatile i32 222, i32* %a1, align 4
+
+  call void @helper_02(i32 0, i32 0, i32 0, i32 0,
+                       i32 0, i32 0, i32 0, i32 0, i32* %a1)
+  ret void
+}
+
+; Check that we do not perform dynamic stack realignment in the presence of
+; the "no-realign-stack" function attribute.
+define void @func_09() "no-realign-stack" {
+entry:
+; ALL-LABEL: func_09:
+
+  ; ALL-NOT:  and     $sp, $sp, $[[T0:[0-9]+|ra|gp]]
+
+  %a = alloca i32, align 512
+  call void @helper_01(i32 0, i32 0, i32 0, i32 0, i32* %a)
+  ret void
+}
+
+define void @func_10(i32 %sz) "no-realign-stack" {
+entry:
+; ALL-LABEL: func_10:
+
+  ; ALL-NOT:  and     $sp, $sp, $[[T0:[0-9]+|ra|gp]]
+
+  %a0 = alloca i32, i32 %sz, align 512
+  %a1 = alloca i32, align 4
+
+  store volatile i32 111, i32* %a0, align 512
+  store volatile i32 222, i32* %a1, align 4
+
+  ret void
+}
diff --git a/llvm/test/CodeGen/Mips/emergency-spill-slot-near-fp.ll b/llvm/test/CodeGen/Mips/emergency-spill-slot-near-fp.ll
index 3dc1cde7709..779620e1012 100644
--- a/llvm/test/CodeGen/Mips/emergency-spill-slot-near-fp.ll
+++ b/llvm/test/CodeGen/Mips/emergency-spill-slot-near-fp.ll
@@ -1,8 +1,8 @@
 ; Check that register scavenging spill slot is close to $fp.
 ; RUN: llc -march=mipsel -O0 < %s | FileCheck %s
 
-; CHECK: sw ${{.*}}, 4($fp)
-; CHECK: lw ${{.*}}, 4($fp)
+; CHECK: sw ${{.*}}, 4($sp)
+; CHECK: lw ${{.*}}, 4($sp)
 
 define i32 @main(i32 signext %argc, i8** %argv) "no-frame-pointer-elim"="true" {
 entry: