ARMFrameLowering: Reserve emergency spill slot for large arguments

Re-commit after revert in r300668. Changed getMaxFPOffset() to a
more conservative heuristic instead of trying to be clever and missing
for some exotic calling conventions.

We need to reserve an emergency spill slot in cases with large argument
types that could overflow immediate offsets for FP relative address
calculations.

rdar://31317893

Differential Revision: https://reviews.llvm.org/D31643

llvm-svn: 300761

1 files changed, 94 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/ARM/fpoffset_overflow.mir b/llvm/test/CodeGen/ARM/fpoffset_overflow.mir
new file mode 100644
index 00000000000..9c6cd931b15
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/fpoffset_overflow.mir
@@ -0,0 +1,94 @@
+# RUN: llc -o - %s -mtriple=thumbv7-- -run-pass=stack-protector -run-pass=prologepilog | FileCheck %s
+---
+# This should trigger an emergency spill in the register scavenger because the
+# frame offset into the large argument is too large.
+# CHECK-LABEL: name: func0
+# CHECK: t2STRi12 killed %r7, %sp, 0, 14, _ :: (store 4 into %stack.0)
+# CHECK: %r7 = t2ADDri killed %sp, 4096, 14, _, _
+# CHECK: %r11 = t2LDRi12 killed %r7, 36, 14, _ :: (load 4)
+# CHECK: %r7 = t2LDRi12 %sp, 0, 14, _ :: (load 4 from %stack.0)
+name: func0
+tracksRegLiveness: true
+fixedStack:
+  - { id: 0, offset: 4084, size: 4, alignment: 4, isImmutable: true,
+      isAliased: false }
+  - { id: 1, offset: -12, size: 4096, alignment: 4, isImmutable: false,
+      isAliased: false }
+body: |
+  bb.0:
+    %r0 = IMPLICIT_DEF
+    %r1 = IMPLICIT_DEF
+    %r2 = IMPLICIT_DEF
+    %r3 = IMPLICIT_DEF
+    %r4 = IMPLICIT_DEF
+    %r5 = IMPLICIT_DEF
+    %r6 = IMPLICIT_DEF
+    %r8 = IMPLICIT_DEF
+    %r9 = IMPLICIT_DEF
+    %r10 = IMPLICIT_DEF
+    %r11 = IMPLICIT_DEF
+    %r12 = IMPLICIT_DEF
+    %lr = IMPLICIT_DEF
+
+    %r11 = t2LDRi12 %fixed-stack.0, 0, 14, _ :: (load 4)
+
+    KILL %r0
+    KILL %r1
+    KILL %r2
+    KILL %r3
+    KILL %r4
+    KILL %r5
+    KILL %r6
+    KILL %r8
+    KILL %r9
+    KILL %r10
+    KILL %r11
+    KILL %r12
+    KILL %lr
+...
+---
+# This should not trigger an emergency spill yet.
+# CHECK-LABEL: name: func1
+# CHECK-NOT: t2STRi12
+# CHECK-NOT: t2ADDri
+# CHECK: %r11 = t2LDRi12 %sp, 4092, 14, _ :: (load 4)
+# CHECK-NOT: t2LDRi12
+name: func1
+tracksRegLiveness: true
+fixedStack:
+  - { id: 0, offset: 4044, size: 4, alignment: 4, isImmutable: true,
+      isAliased: false }
+  - { id: 1, offset: -12, size: 4056, alignment: 4, isImmutable: false,
+      isAliased: false }
+body: |
+  bb.0:
+    %r0 = IMPLICIT_DEF
+    %r1 = IMPLICIT_DEF
+    %r2 = IMPLICIT_DEF
+    %r3 = IMPLICIT_DEF
+    %r4 = IMPLICIT_DEF
+    %r5 = IMPLICIT_DEF
+    %r6 = IMPLICIT_DEF
+    %r8 = IMPLICIT_DEF
+    %r9 = IMPLICIT_DEF
+    %r10 = IMPLICIT_DEF
+    %r11 = IMPLICIT_DEF
+    %r12 = IMPLICIT_DEF
+    %lr = IMPLICIT_DEF
+
+    %r11 = t2LDRi12 %fixed-stack.0, 0, 14, _ :: (load 4)
+
+    KILL %r0
+    KILL %r1
+    KILL %r2
+    KILL %r3
+    KILL %r4
+    KILL %r5
+    KILL %r6
+    KILL %r8
+    KILL %r9
+    KILL %r10
+    KILL %r11
+    KILL %r12
+    KILL %lr
+...