[ARM] Fix insert point for store rescheduling.

In ARMPreAllocLoadStoreOpt::RescheduleOps, LastOp should be the last
operation which we want to merge. If we break out of the loop because
an operation has the wrong offset, we shouldn't use that operation
as LastOp.

This patch fixes some cases where we would move stores to the wrong
insert point.

Re-commit with a fix to increment NumMove in the right place.

Differential Revision: https://reviews.llvm.org/D30124

llvm-svn: 296815

llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp

@@ -2161,33 +2161,40 @@ bool ARMPreAllocLoadStoreOpt::RescheduleOps(MachineBasicBlock *MBB,
     unsigned LastBytes = 0;
     unsigned NumMove = 0;
     for (int i = Ops.size() - 1; i >= 0; --i) {
+      // Make sure each operation has the same kind.
       MachineInstr *Op = Ops[i];
-      unsigned Loc = MI2LocMap[Op];
-      if (Loc <= FirstLoc) {
-        FirstLoc = Loc;
-        FirstOp = Op;
-      }
-      if (Loc >= LastLoc) {
-        LastLoc = Loc;
-        LastOp = Op;
-      }
-
       unsigned LSMOpcode
         = getLoadStoreMultipleOpcode(Op->getOpcode(), ARM_AM::ia);
       if (LastOpcode && LSMOpcode != LastOpcode)
         break;
 
+      // Check that we have a continuous set of offsets.
       int Offset = getMemoryOpOffset(*Op);
       unsigned Bytes = getLSMultipleTransferSize(Op);
       if (LastBytes) {
         if (Bytes != LastBytes || Offset != (LastOffset + (int)Bytes))
           break;
       }
+
+      // Don't try to reschedule too many instructions.
+      if (NumMove == 8) // FIXME: Tune this limit.
+        break;
+
+      // Found a mergable instruction; save information about it.
+      ++NumMove;
       LastOffset = Offset;
       LastBytes = Bytes;
       LastOpcode = LSMOpcode;
-      if (++NumMove == 8) // FIXME: Tune this limit.
-        break;
+
+      unsigned Loc = MI2LocMap[Op];
+      if (Loc <= FirstLoc) {
+        FirstLoc = Loc;
+        FirstOp = Op;
+      }
+      if (Loc >= LastLoc) {
+        LastLoc = Loc;
+        LastOp = Op;
+      }
     }
 
     if (NumMove <= 1)

llvm/test/CodeGen/ARM/ldm-stm-i256.ll

@@ -0,0 +1,38 @@
+; RUN: llc -mtriple=armv7--eabi -verify-machineinstrs < %s | FileCheck %s
+
+; Check the way we schedule/merge a bunch of loads and stores.
+; Originally test/CodeGen/ARM/2011-07-07-ScheduleDAGCrash.ll ; now
+; being used as a test of optimizations related to ldm/stm.
+
+; FIXME: We could merge more loads/stores with regalloc hints.
+; FIXME: Fix scheduling so we don't have 16 live registers.
+
+define void @f(i256* nocapture %a, i256* nocapture %b, i256* nocapture %cc, i256* nocapture %dd) nounwind uwtable noinline ssp {
+entry:
+  %c = load i256, i256* %cc
+  %d = load i256, i256* %dd
+  %add = add nsw i256 %c, %d
+  store i256 %add, i256* %a, align 8
+  %or = or i256 %c, 1606938044258990275541962092341162602522202993782792835301376
+  %add6 = add nsw i256 %or, %d
+  store i256 %add6, i256* %b, align 8
+  ret void
+  ; CHECK-DAG: ldm r3
+  ; CHECK-DAG: ldm r2
+  ; CHECK-DAG: ldr {{.*}}, [r3, #20]
+  ; CHECK-DAG: ldr {{.*}}, [r3, #16]
+  ; CHECK-DAG: ldr {{.*}}, [r3, #28]
+  ; CHECK-DAG: ldr {{.*}}, [r3, #24]
+  ; CHECK-DAG: ldr {{.*}}, [r2, #20]
+  ; CHECK-DAG: ldr {{.*}}, [r2, #16]
+  ; CHECK-DAG: ldr {{.*}}, [r2, #28]
+  ; CHECK-DAG: ldr {{.*}}, [r2, #24]
+  ; CHECK-DAG: stmib r0
+  ; CHECK-DAG: str {{.*}}, [r0]
+  ; CHECK-DAG: str {{.*}}, [r0, #24]
+  ; CHECK-DAG: str {{.*}}, [r0, #28]
+  ; CHECK-DAG: str {{.*}}, [r1]
+  ; CHECK-DAG: stmib r1
+  ; CHECK-DAG: str {{.*}}, [r1, #24]
+  ; CHECK-DAG: str {{.*}}, [r1, #28]
+}

llvm/test/CodeGen/ARM/prera-ldst-insertpt.mir

@@ -36,19 +36,22 @@ body:             |
     t2STRi12 %1, %0, 0, 14, _ :: (store 4)
     %10 : rgpr = t2LSLri %2, 1, 14, _, _
     t2STRi12 killed %10, %0, 4, 14, _ :: (store 4)
+
+    ; Make sure we move the paired stores next to each other, and
+    ; insert them in an appropriate location.
+    ; CHECK: t2STRi12 %1,
+    ; CHECK-NEXT: t2STRi12 killed %10,
+    ; CHECK-NEXT: t2MOVi
+    ; CHECK-NEXT: t2ADDrs
+
     %11 : rgpr = t2MOVi 55, 14, _, _
     %12 : gprnopc = t2ADDrs %11, killed %7, 19, 14, _, _
     t2STRi12 killed %12, %0, 16, 14, _ :: (store 4)
     %13 : gprnopc = t2ADDrs %11, killed %9, 19, 14, _, _
     t2STRi12 killed %13, %0, 20, 14, _ :: (store 4)
 
     ; Make sure we move the paired stores next to each other.
-    ; FIXME: Make sure we don't extend the live-range of a store
-    ; when we don't need to.
-    ; CHECK: t2STRi12 %1,
-    ; CHECK-NEXT: t2STRi12 killed %10,
-    ; CHECK-NEXT: %13 = t2ADDrs %11
-    ; CHECK-NEXT: t2STRi12 killed %12,
+    ; CHECK: t2STRi12 killed %12,
     ; CHECK-NEXT: t2STRi12 killed %13,
 
     tBX_RET 14, _
@@ -73,6 +76,15 @@ body:             |
     t2STRi12 killed %10, %0, 4, 14, _ :: (store 4)
     %3 : rgpr = t2MUL %2, %2, 14, _
     t2STRi12 %3, %0, 8, 14, _ :: (store 4)
+
+    ; Make sure we move the paired stores next to each other, and
+    ; insert them in an appropriate location.
+    ; CHECK: t2STRi12 {{.*}}, 0
+    ; CHECK-NEXT: t2STRi12 {{.*}}, 4
+    ; CHECK-NEXT: t2STRi12 {{.*}}, 8
+    ; CHECK-NEXT: t2MUL
+    ; CHECK-NEXT: t2MOVi32imm
+
     %4 : rgpr = t2MUL %1, %1, 14, _
     %5 : rgpr = t2MOVi32imm -858993459
     %6 : rgpr, %7 : rgpr  = t2UMULL killed %3, %5, 14, _
@@ -85,13 +97,7 @@ body:             |
     t2STRi12 killed %13, %0, 20, 14, _ :: (store 4)
 
     ; Make sure we move the paired stores next to each other.
-    ; FIXME: Make sure we don't extend the live-range of a store
-    ; when we don't need to.
-    ; CHECK: t2STRi12 {{.*}}, 0
-    ; CHECK-NEXT: t2STRi12 {{.*}}, 4
-    ; CHECK-NEXT: t2STRi12 {{.*}}, 8
-    ; CHECK-NEXT: t2ADDrs
-    ; CHECK-NEXT: t2STRi12 {{.*}}, 16
+    ; CHECK: t2STRi12 {{.*}}, 16
     ; CHECK-NEXT: t2STRi12 {{.*}}, 20
 
     tBX_RET 14, _