ARM Ld/St Optimizer fix.

Allow LDRD to be formed from pairs with different LDR encodings. This was the original intention of the pass. Somewhere along the way, the LDR opcodes were refined which broke the optimization. We really don't care what the original opcodes are as long as they both map to the same LDRD and the immediate still fits.

Fixes rdar://10435045 ARMLoadStoreOptimization cannot handle mixed LDRi8/LDRi12

llvm-svn: 147922

2 files changed, 50 insertions, 3 deletions

diff --git a/llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp b/llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
index 6712fb6e9ad..af6a5b8d120 100644
--- a/llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
+++ b/llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp
@@ -1639,8 +1639,9 @@ bool ARMPreAllocLoadStoreOpt::RescheduleOps(MachineBasicBlock *MBB,
         LastOp = Op;
       }
 
-      unsigned Opcode = Op->getOpcode();
-      if (LastOpcode && Opcode != LastOpcode)
+      unsigned LSMOpcode
+        = getLoadStoreMultipleOpcode(Op->getOpcode(), ARM_AM::ia);
+      if (LastOpcode && LSMOpcode != LastOpcode)
         break;
 
       int Offset = getMemoryOpOffset(Op);
@@ -1651,7 +1652,7 @@ bool ARMPreAllocLoadStoreOpt::RescheduleOps(MachineBasicBlock *MBB,
       }
       LastOffset = Offset;
       LastBytes = Bytes;
-      LastOpcode = Opcode;
+      LastOpcode = LSMOpcode;
       if (++NumMove == 8) // FIXME: Tune this limit.
         break;
     }
diff --git a/llvm/test/CodeGen/ARM/ldrd.ll b/llvm/test/CodeGen/ARM/ldrd.ll
index d72e9bfc1da..a588bc31535 100644
--- a/llvm/test/CodeGen/ARM/ldrd.ll
+++ b/llvm/test/CodeGen/ARM/ldrd.ll
@@ -1,6 +1,8 @@
 ; RUN: llc < %s -mtriple=thumbv7-apple-ios -mcpu=cortex-a8 -regalloc=fast | FileCheck %s -check-prefix=A8
 ; RUN: llc < %s -mtriple=thumbv7-apple-ios -mcpu=cortex-m3 -regalloc=fast | FileCheck %s -check-prefix=M3
 ; rdar://6949835
+; RUN: llc < %s -mtriple=thumbv7-apple-ios -mcpu=cortex-a8 -regalloc=basic | FileCheck %s -check-prefix=BASIC
+; RUN: llc < %s -mtriple=thumbv7-apple-ios -mcpu=cortex-a8 -regalloc=greedy | FileCheck %s -check-prefix=GREEDY
 
 ; Magic ARM pair hints works best with linearscan / fast.
 
@@ -23,3 +25,47 @@ entry:
 	%2 = mul i64 %1, %a
 	ret i64 %2
 }
+
+; rdar://10435045 mixed LDRi8/LDRi12
+;
+; In this case, LSR generate a sequence of LDRi8/LDRi12. We should be
+; able to generate an LDRD pair here, but this is highly sensitive to
+; regalloc hinting. So, this doubles as a register allocation
+; test. RABasic currently does a better job within the inner loop
+; because of its *lack* of hinting ability. Whereas RAGreedy keeps
+; R0/R1/R2 live as the three arguments, forcing the LDRD's odd
+; destination into R3. We then sensibly split LDRD again rather then
+; evict another live range or use callee saved regs. Sorry if the test
+; is sensitive to Regalloc changes, but it is an interesting case.
+;
+; BASIC: @f
+; BASIC: %bb
+; BASIC: ldrd
+; BASIC: str
+; GREEDY: @f
+; GREEDY: %bb
+; GREEDY: ldr
+; GREEDY: ldr
+; GREEDY: str
+define void @f(i32* nocapture %a, i32* nocapture %b, i32 %n) nounwind {
+entry:
+  %0 = add nsw i32 %n, -1                         ; <i32> [#uses=2]
+  %1 = icmp sgt i32 %0, 0                         ; <i1> [#uses=1]
+  br i1 %1, label %bb, label %return
+
+bb:                                               ; preds = %bb, %entry
+  %i.03 = phi i32 [ %tmp, %bb ], [ 0, %entry ]    ; <i32> [#uses=3]
+  %scevgep = getelementptr i32* %a, i32 %i.03     ; <i32*> [#uses=1]
+  %scevgep4 = getelementptr i32* %b, i32 %i.03    ; <i32*> [#uses=1]
+  %tmp = add i32 %i.03, 1                         ; <i32> [#uses=3]
+  %scevgep5 = getelementptr i32* %a, i32 %tmp     ; <i32*> [#uses=1]
+  %2 = load i32* %scevgep, align 4                ; <i32> [#uses=1]
+  %3 = load i32* %scevgep5, align 4               ; <i32> [#uses=1]
+  %4 = add nsw i32 %3, %2                         ; <i32> [#uses=1]
+  store i32 %4, i32* %scevgep4, align 4
+  %exitcond = icmp eq i32 %tmp, %0                ; <i1> [#uses=1]
+  br i1 %exitcond, label %return, label %bb
+
+return:                                           ; preds = %bb, %entry
+  ret void
+}