[ARM] Don't generate deprecated T1 STM.

    
This prevents generating stm r1!, {r0, r1} on Thumb1, where value
stored for r1 is UNKONWN.

Patch by Zhaoshi Zheng.

Differential Revision: https://reviews.llvm.org/D27910

llvm-svn: 296538

2 files changed, 22 insertions, 4 deletions

diff --git a/llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp b/llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
index c87f70397b7..8e51f136b32 100644
--- a/llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
+++ b/llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
@@ -609,13 +609,12 @@ MachineInstr *ARMLoadStoreOpt::CreateLoadStoreMulti(
   // Exception: If the base register is in the input reglist, Thumb1 LDM is
   // non-writeback.
   // It's also not possible to merge an STR of the base register in Thumb1.
-  if (isThumb1 && isi32Load(Opcode) && ContainsReg(Regs, Base)) {
+  if (isThumb1 && ContainsReg(Regs, Base)) {
     assert(Base != ARM::SP && "Thumb1 does not allow SP in register list");
-    if (Opcode == ARM::tLDRi) {
+    if (Opcode == ARM::tLDRi)
       Writeback = false;
-    } else if (Opcode == ARM::tSTRi) {
+    else if (Opcode == ARM::tSTRi)
       return nullptr;
-    }
   }
 
   ARM_AM::AMSubMode Mode = ARM_AM::ia;
diff --git a/llvm/test/CodeGen/Thumb/stm-deprecated.ll b/llvm/test/CodeGen/Thumb/stm-deprecated.ll
new file mode 100644
index 00000000000..ffe2c0afd92
--- /dev/null
+++ b/llvm/test/CodeGen/Thumb/stm-deprecated.ll
@@ -0,0 +1,19 @@
+; RUN: llc -mtriple=thumbv6m-eabi -verify-machineinstrs %s -o - | FileCheck %s
+; RUN: llc -mtriple=thumbv5e-linux-gnueabi -verify-machineinstrs %s -o - | FileCheck %s
+
+%0 = type { %0*, %0*, i32 }
+
+@x1 = external global %0, align 4
+@x2 = external global %0, align 4
+
+; CHECK: str r0, [r1]
+; CHECK-NEXT: str r1, [r1, #4]
+; CHECK-NOT: stm
+
+define void @foo(i32 %unused, %0* %x) {
+  %first = getelementptr inbounds %0, %0* %x, i32 0, i32 0
+  %second = getelementptr inbounds %0, %0* %x, i32 0, i32 1
+  store %0* @x1, %0** %first
+  store %0* %x, %0** %second
+  unreachable
+}